Table of Contents
Section A: The Business of Farming .............................................................................................. 2
Role and Importance of Agriculture ........................................................................................... 2
Challenges Confronting Agriculture ........................................................................................... 9
Alternative to Conventional Farming ....................................................................................... 20
Economic Factors of Production ............................................................................................... 27
Trade Agreements ..................................................................................................................... 46
Farm Financing and Support Services ...................................................................................... 50
Farm Organization and Planning .............................................................................................. 57
Section B: Crop Production .......................................................................................................... 66
Soil and Soil Fertility ................................................................................................................ 66
Land Preparation ....................................................................................................................... 93
Plant Morphology and Physiology ......................................................................................... 106
Plant Genetics, Breeding and Biotechnology ......................................................................... 128
Crop Husbandry ...................................................................................................................... 136
Harvesting and Postharvest Practices ..................................................................................... 153
Processing and Utilization ...................................................................................................... 158
Section C: Animal Production .................................................................................................... 164
Morphology and Physiology ................................................................................................... 164
Nutrition .................................................................................................................................. 170
Housing ................................................................................................................................... 183
Animal Genetics, Breeding and Reproduction ....................................................................... 191
Animal Husbandry .................................................................................................................. 209
Animal Products Technology .................................................................................................. 220
Section A: The Business of Farming
Role and Importance of Agriculture
1. Discuss the role and importance of agriculture in national, regional, and international
economies.
Foreign exchange earnings
Agriculture is very important to the economies of all Caribbean countries, both regionally and
internationally. When Caribbean agricultural goods and services are sold to other countries,
foreign exchange is earned. For example, the export of bananas and coffee earns foreign
currency. However, when foreign agricultural goods and services are imported, Caribbean
currency is converted to foreign exchange; importing agricultural machinery from abroad is
therefore a loss to the local community.
Contribution to Gross National Product
Gross National Product (GNP is a measure of the current value of goods and services from all
sectors of the national economy. Agriculture is a vital sector of the national economy and
contributes to the GNP.
Food security
Food security means being self-sufficient in food.
Food security is encouraging self-sufficiency by promoting and improving food production and
marketing. This will expand trade opportunities, increase the national income, and improve
nutrition. Food security should reduce dependence on imported foods by promoting the
development of food production locally.
Most Caribbean countries are now boosting their local food production and reducing food
imports.
In the Caribbean, food security is affected by:
• low agricultural productivity, resulting from inefficient use of water and other inputs
• a decline in earnings from traditional crops resulting from the loss of trade preferences
• a dependency on imported food resulting from the inability to produce food locally at
competitive prices
• increased poverty in many countries because of a loss of agricultural jobs.
Food security can be promoted by initiatives to improve food production and marketing, expand
trade opportunities, increase income, and improve nutrition.
Employment ratio of imported food to local produce
The agricultural sector can provide employment for many people. There is a wide range of job
opportunities, such as farming, agricultural education, marketing, engineering, and farm
management. Improved agricultural production improves the employment prospects of a region
— if more food is grown locally then more jobs are created. Importing food from abroad reduces
the number of local agricultural jobs. There is also concern about the quality of some of the food
imported into the Caribbean. It is thought that some imported food may be responsible for an
obesity problem within the population.
National and regional plans for agricultural development
Agricultural plans are policy documents, prepared by governments, private firms or international
organisations, setting out plans for agricultural development. Normally, local or national plans
are prepared by the government of each Caribbean country for a five-year period. The plan for
each country identifies the areas of agriculture which need attention and may specify the current
status, constraints, strategies, and resources required for the development of each area. Carefully
prepared plans can bring about agricultural development and national development. Regional
plans for agricultural development are produced through the cooperative efforts of Caribbean
countries, based on the agricultural needs of the region. Specific goals, objectives, constraints,
strategies, resources, and evaluation procedures help to put the plans into practice.
Trade liberalisation
Trade liberalisation helps global competitiveness. A fair trade in goods and services develops
through removing tariffs and non-tariff barriers. A tariff is a tax levied by a government on
imports (or occasionally exports) for purposes of protection, support of the balance of payments,
or the raising of revenue. Global trade liberalisation initiatives encourage greater efficiency in
marketing and trade by restructuring trade policy regimes to reduce the level of protection from
competition. Trade liberalisation does not just depend on the removal of barriers and the
economy of a country for each government in the formulation of their trade policies. This should
result in each country being encouraged to improve productivity in agriculture and making
greater efforts to improve the quality of agricultural products
2. List the various career opportunities in the agricultural sector
Careers in:
(a) sales
(b) services
(c) marketing
(d) production
(e) education
(f) agroprocessing
(g) journalism
(h) engineering
(i) administration
(j) management
(k) quality control
(l) food inspection
(m) certification
3. State the functions of local, regional, and international institutions concerned with
agricultural development in the Caribbean
Local:
Local institutions, both governmental and non-governmental, are essential for any modem
agricultural economy. The quality of the support mechanisms determines the quality of the
agricultural output. More importantly, it creates a sound foundation for new initiatives, growth
and expansion in the agricultural sector.
Ministry of Agriculture (MA)
Each Ministry of Agriculture is divided into several divisions which work in collaboration with
affiliated agencies, farmers' organisations, and commercial agri-businesses to provide support
services to farmers and agriculturalists for agricultural development.
Regional:
There are many institutions in the Caribbean concerned with agricultural development. Some
give advice and support, whilst others provide specialised training for careers in the agricultural
sector.
(a) Caribbean Community (CARICOM)
CARICOM is an organisation of 15 Caribbean nations and dependencies. It promotes economic
integration and co-operation.
CARICOM carries out these functions:
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co-ordinates economic policies and development planning
sets up special projects for less-developed countries
operates as a regional single market for many of its members (Caricom Single Market)
handles regional trade disputes.
(b) Caribbean Food and Nutrition Institute (CFNI)
CFNI aims to describe, manage and prevent nutritional problems facing Caribbean countries. It
runs training courses, conducts research programmes on food and nutrition and maintains a
library.
Research areas include:
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reduction of under-nutrition in children
prevention and control of diet-related chronic diseases
control of iron deficiency anaemia
improvement of household food security.
(c) Caribbean Development Bank (CDB)
CDB assists Caribbean nations in financing projects for its members. Its purpose is to contribute
to the economic growth and development of member countries and to promote economic cooperation and integration.
Its main functions are to:
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assist members in the co-ordination of their development programmes with a view to
achieving better utilisation of their resources, making their economies more
complementary, and promoting the orderly expansion of their international trade
mobilise additional financial resources for the development of the region
finance projects and programmes contributing to the development of the region
provide technical assistance to regional members
promote private and public investment in development projects
stimulate and encourage the development of capital markets within the region.
(d) Caribbean Agricultural Research and Development Institute (CARDI)
CARDI conducts research and demonstrates appropriate technologies to farmers.
CARDI provides technical assistance in areas such as:
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crop production, integrated pest management (IPM) and farming systems
livestock and forages
environmental and soils management technology services, e.g., the supply of quality
plant products and genetic products and services market research and statistical services
business development and consultancy.
(e) The University of the West Indies (UWI)
UWI, Faculty of Science and Agriculture, offers a wide range of courses leading to qualifications
(from diplomas to post-graduate degrees). Qualifications can be obtained in Natural Sciences,
such as Life Sciences and Chemistry, and aspects of agriculture, such as Animal Science, Food
Production, Economics and Extension Services. In addition, research units investigate specific
problems relating to crop and livestock production.
(f) College of Agriculture, Science and Education (CASE) [formerly JSA]
CASE, in Jamaica, is a multi-disciplinary tertiary level educational institution offering diplomas,
associate degrees and bachelor’s degrees. Of particular relevance are its bachelor’s degree
courses in Business Studies, Environmental Science and Agri-production and Food Systems
Management. There are associate degree courses in General Agriculture, Agricultural Education,
Natural Science and Business Studies. There are also courses leading to diplomas in Agriculture
and teaching qualifications. The Department of Animal Science helps to increase productivity of
livestock, and the Department of Plant, Soil Sciences and Engineering provides training in
Agronomy, Plant Science, Soil Science, Horticulture, Land Surveying, Plant Protection and Crop
Production. The diploma in Agriculture was designed to train skilled practitioners in specific
areas of agriculture, who would put their training into practice on farms and in other agricultural
enterprises. An Associate of Science degree trains students to be highly competent farmers and
'agri-preneurs'. This qualification enables graduates to enter most jobs that require a knowledge
of agriculture.
(g) Eastern Caribbean Institute of Agriculture and Forestry (ECIAF)
ECIAF provides courses that last two years and lead to diplomas in Agriculture, Forestry and
Agricultural Education. Completion of a diploma enables students to gain employment in
agriculture, forestry, or education, or to enter other courses in higher education if they wish to.
(h) Guyana School of Agriculture (GSA)
GSA provides training to certificate and diploma level in agriculture. The one-year course
leading to a certificate in Forest» trains students to become forestry technicians and teaches them
the principle of sustainable forestry. A two-year certificate course equips young people for
careers in farming. The diploma courses last for two years and lead to careers as Agricultural
Science teachers or agricultural field assistants. These courses are ii Agriculture, Animal Health,
Veterinary Public Health and Livestock Production and Management.
International:
The Caribbean nations are part of the global economy — agricultural development therefore
depends on international institutions as well as local and regional organisations.
(a) European Union (EU)
In October 2008, the 27 members of the European Union (EU) and 15 Caribbean nations signed
an Economic Partnership Agreement (EPA). It included measures to stimulate trade, investment
and innovation, and to promote sustainable development, build a regional market among
Caribbean countries and help eliminate poverty. The effect will be to open up markets for
produce from the Caribbean countries by removing tariffs and encouraging trade liberalisation.
The agreement is important for the economies of Caribbean countries and encourages fair trade
for commodities such as sugar, coffee and bananas.
(b) Inter-American Institute for Cooperation on Agriculture (IICA)
IICA is an institution for agricultural research and graduate training in tropical agriculture. It was
founded in response to changing needs in the Americas and has evolved into an agency for
technical co-operation in the field of agriculture, promoting agricultural development and rural
well-being.
The IICA supports and encourages:
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agro-energy and biofuels
biotechnology and biosafety
rural communities
trade and agribusiness
trade negotiations
institutional modernisation
technology and innovation
environmental management
agricultural health
organic agriculture.
(c) Food and Agriculture Organization (FAO)
FAO of the United Nations leads international efforts to defeat hunger. It helps countries to
modernise and improve agriculture, forestry and fisheries practices and ensures good nutrition
for all.
Within the organisation, there are departments for:
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agriculture and consumer protection
economic and social development
fisheries and aquaculture
forestry
natural resources management and environment
technical co-operation.
There are regional, sub-regional, country and liaison offices worldwide. There is a sub-regional
office for the Caribbean in Barbados and country offices in many Caribbean countries.
(d) Organization of American States (OAS)
OAS is made up of 35 independent nations of the Americas. It was founded in 1948 with 21
members but expanded to include the independent Caribbean nations. The goal of member
nations was to 'achieve an order of peace and justice, to promote solidarity, to strengthen
collaboration, and to defend sovereignty, territorial integrity and independence'. It seeks to
promote economic, social, and cultural development and to eradicate extreme poverty.
(e) Inter-American Development Bank (IDB)
IDB is an international organisation established to support Latin American and Caribbean
economic and social development and regional integration. It is the largest multilateral source of
financing and lends money mainly to governments and government agencies. The bank is owned
by 47 member states of which 26, including the Caribbean countries, can borrow money and 21
others cannot. There are some criticisms of the way in which it works. Some of the projects are
considered to be damaging to local environments and local people.
(f) Canadian International Development Agency (CIDA)
CIDA is the federal body that Development Agency funds assistance to developing countries in
the form of goods, services, the transfer of knowledge and skills, and humanitarian relief in
emergencies and for natural disasters.
CIDA advises on many topics including:
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food
nutrition
agriculture
rural development
co-operatives
• fisheries
• forestry
• water management
• the environment
• health and population
Experts broaden the scope of the CIDA beyond financial support and help developing countries
to take charge of their own economies. In addition, skilled workers and technicians are sent to
developing countries. Trainees may also take up scholarships in Canada.
CIDA funds many projects, such as:
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providing supplements to children with vitamin A
global immunisation programmes
supporting HIV/AIDS prevention, education, and care.
Agriculture covers a wide range of subject areas and is therefore a 'multi-faceted
discipline'.
Agriculture is a key sector of the Caribbean economy. It makes a significant development
in the GNP and to foreign exchange earnings.
The production of food locally is encouraged so that more opportunities for employment
are created.
Careful planning is needed to bring about agricultural development and boost local
agricultural county office the national economy and regional economy.
Global trade liberalisation encourages improvement in agricultural productivity, greater
efficiency in marketing and fair trade for goods and services.
There are many career choices in the agricultural sector; there are employment
opportunities for skilled and unskilled people in all aspects of food production and
marketing.
The Ministry of Agriculture in each Caribbean country, together with other agencies and
institutions, provides support services for agricultural development.
In the Caribbean, there are institutions providing advice and support to the agricultural
sector, as well as some which provide specialised careers training.
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Caribbean countries are part of the global economy; their agricultural development
depends on contributions from international organisations.
Challenges Confronting Agriculture
4. Discuss the major challenges affecting local and regional agriculture
Climate
Agricultural production is directly affected by climatic conditions. For any period, production
may be high or low depending on the weather conditions. There are two distinct seasons: a dry
season and a wet season, although the months comprising the two seasonal periods vary slightly
in some Caribbean states.
In the dry season, there is plenty of sunshine, high temperatures and a shortage of water,
especially for crop irrigation. As a result, crop cultivation is not possible in areas where there is
no water.
The wet season has heavy rainfall, cool temperatures, high humidity. and strong winds, including
hurricanes. Farmers are challenged to control pests and diseases, which are more common during
the rainy season. In addition, crops and livestock are damaged by floods and strong winds.
Strategies for coping with climate
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In the dry season, farmers conserve soil water by cultural practices, such as organic
mulching, incorporating pen manure and other organic matter into the soil, and
transplanting seedlings into concave 'pockets' to keep soil water within the root zone.
In the rainy season, drainage systems are essential. Farmers use cambered beds and
ridges for crop cultivation, and practise pruning and staking of crops.
Governments can assist farmers, by means of subsidies, to establish ponds to reduce the
disastrous effects of flooding and to store water during the dry season.
Similarly, governments, through the Forestry Division, can help farmers to establish
windbreaks in areas where crops are prone to wind disasters.
Topography
The topography, or external features of the land, affects methods of cultivation and crop
production. Farmers prefer to cultivate land which is flat or undulating because movement of
machinery and equipment for land preparation, crop harvesting, and transportation of produce is
easier. Figure 2.1 Hilly terrain — machines are difficult to operate in these areas.
However, most of the Caribbean is hilly or mountainous. There are no alternatives to the use of
manual methods for most field operations in hilly areas. Mountainous areas have shallow topsoil
and are prone to soil erosion and landslips. Farmers can carry out strip cropping, cover cropping,
contouring, and terracing. However, these options are not always easy. The erection of barriers of
stone, wood or grass is expensive, although these can help to control soil erosion.
Mechanisation in hilly areas
Mechanisation allows farmers to complete agricultural tasks more speedily and efficiently. This
increases their production and profitability. However, in the Caribbean there is limited use of
mechanisation due to hills and mountains. There is some use of machinery: the sugar cane and
rice industries in Guyana and Trinidad and Tobago are fully mechanised. Limited use is also
made of machinery in land preparation, milking cows, plucking chickens, application of
pesticides, weed control and crop irrigation. Across the Caribbean, regional governments and
private firms need to introduce mechanisation. This mechanisation should be appropriate for the
terrain and reasonably priced for farmers.
Rural infrastructure
In the Caribbean, rural communities have often developed into villages and towns as a result of
agriculture. Sometimes the infrastructure has been developed on a planned basis to help farming
communities. Infrastructure refers to the basic services and installations needed for a community
to function, such as transportation and communications systems, water and power lines, and
public institutions including schools.
However, nationally, and regionally, many rural areas still lack an essential infrastructure. Often
there is no incentive for farmers to continue living in these areas, where they experience hardship
because of few basic amenities. Roads, a water supply, electricity and telephones, educational,
medical, and recreational facilities all need to be available. Many rural areas lack shops and
public transport systems.
Farmers want their families to have a better lifestyle and therefore they often migrate to urban
areas. This rural-to-urban drift causes abandonment of agricultural land, absentee farmers, a
shortage of agricultural labour and a lowering of agricultural production. The governments of
Caribbean countries need to address the needs of farmers in rural communities. Investment in
rural infrastructure is the pathway to greater agricultural productivity and food security.
Extension services
There is a worldwide pool of technical knowledge about agriculture, gained from developments
in science. This knowledge can be used to help agricultural development and food security. With
modern communication links and internet services, many regional territories have websites from
which farmers can access technical agricultural information.
Throughout the Caribbean, extension officers make farmers aware of the latest developments in
agriculture and encourage them to adopt modem technology. In some countries there are not
enough extension officers. In addition, training centres are not always equipped to provide the
training and practical demonstrations needed to convince farmers of the benefits of new
practices. This results in reluctance to use new technical knowledge without first seeing whether
it will really work. Local and regional governments need to train more extension officers and
provide well-equipped training centres.
Praedial larceny
Praedial larceny is stealing agricultural produce, such as crops and livestock, and it causes severe
economic losses to farmers. This crime deprives farmers of the opportunity of harvesting what
they have planted and nurtured and robs them of hard-earned dollars. This is a problem,
especially for farmers who cultivate crops which are easy to harvest (for example, bananas,
watermelons, pumpkins, cabbages, corn, and cucumbers). Often, farmers or other family
members have to stay on the farm day and night or hire a security officer. The culprits are not
always caught. In addition, complaints to the police do not always yield a desirable response. It
may be difficult to identify offenders and bring them to justice. The few who have been caught in
the act have had low fines imposed by the courts. As a result, some farmers, especially those
regularly targeted, have given up commercial farming.
Local and regional governments need to address the problem with strategies such as:
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hiring praedial larceny officers (estate police) or encouraging farmers' co-operatives to
hire praedial larceny officers
conducting regular police checks in rural districts
imposing more severe fines on offenders
raising public awareness of this crime.
Land tenure systems
Land tenure refers to the rights and conditions under which people hold, own, use, control and
enjoy property (land). For the farmer, land is necessary for agricultural production and is a vital
resource. Traditionally, parents have handed down land as a legacy to their children. With each
generation, sub-division of the land has resulted in fragmentation. Often parcels of land have
become too small to be run as economically viable (land is handed down through the farming
units. generations). Some landowners are not interested in farming the land themselves but allow
farmers to rent it or enter into a share-cropping arrangement. The farmers who rent the land are
known as tenant farmers. Tenant farmers are not always keen on managing the land properly or
carrying out soil improvements, because the land is not their own and they can be evicted at short
notice.
Loss of agricultural land
In the Caribbean, land is a symbol of economic power. As time passes, land often appreciates
(rises) in value; it may be used for commercial purposes and housing, provided that approval is
granted by the government. Land is a scarce resource: it warrants careful use and land reform
policies for state lands and areas that are idle or abandoned by their owners. Each Caribbean
state needs to ensure that agricultural lands are identified and mapped out, and also allocated by
means of a land tenure system to farmers 'for agricultural production and national food security.
In some countries, tougher measures are needed to ensure that good agricultural land is not used
for the development of residential areas.
Sustainable land use
More sustainable management of land can reverse land degradation and desertification. But
management of land resources needs to be improved if it is to address the following problems:
loss of soil fertility, reduction in freshwater resources, loss of biological diversity and
degradation of coastal ecosystems. Sustainable land use is a term which means planning and
managing land for agriculture, settlement development, tourism, forestry, and livestock. To
increase sustainable land use within the region, a partnership of national, regional and I
international organisations with farming and forestry communities has been proposed. The
partnership will look at integrated land use management, appropriate technologies, food security,
economic development, and environmental protection.
Environmental issues
Farmers interact with the natural environment by removing vegetation, tilling the soil,
introducing new plant species, spraying with pesticides, and modifying microclimatic conditions.
Although necessary for food production, environmentalists worry about the harmful effects of
these farming practices.
The major concerns relevant to agriculture are:
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destruction of ecosystems
loss of biodiversity
build-up of pollution
pesticide resistance.
Food safety
More people now travel within the Caribbean region and all over the world for business and
pleasure. Some may visit farms abroad and inadvertently bring seed, plant, soil, or animal
materials into their home country. These materials may harbour pests and diseases which can
spread rapidly and cause havoc to domestic agriculture.
Nationally and regionally, sanitary, and Phyto-sanitary (SPS) certification procedures govern the
import and export of plants, animals and their products. Normally, licences are issued for import
and export purposes. Incoming plants and animals are quarantined for observation, testing and
certification of their disease-free status before release for propagation in the country.
Governments sometimes impose restrictions on the import of certain agricultural products, such
as poultry (chickens, eggs) and beef, from countries which have experienced 'bird flu' or 'mad
cow' disease. Agricultural workers associated with these outbreaks are also monitored to ensure
that diseases are not transmitted to other farms and that no agricultural pests• or diseases are
brought into their home country.
Natural disasters
Each year, Caribbean countries are threatened by loss of life, property damage and social
disruption as a result of natural disasters. Tropical storms, hurricanes, tidal waves, heavy rains,
and droughts have occurred in the last 30 years. Disasters have cost the region billions of dollars
and damaged economic health and development. The Caribbean Disaster Emergency Response
Agency (CDERA) has developed a strategy for the management of such disasters, known as the
CDM (Comprehensive Disaster Management) strategy. This places emphasis on the benefits of
strengthening the infrastructure so that installations are as storm-resistant as possible. Investment
in roads, drainage systems, electrical and water services, schools, and hospitals saves money in
the long term, as the cost of clean-up procedures is usually greater and involves rehabilitation
and total rebuilding. This strategy depends on persuading individual governments to make
investments — this is always a challenge.
Gender issues and agriculture
During the colonial era, women in Caribbean countries were paid lower agricultural wages than
men (for the same number of hours and type of work). In addition, women were barred from
holding managerial positions in the agricultural sector as well as in other occupations. At that
time, men saw themselves as being superior to women, who played subservient roles in the home
and workplace. Most men felt that it was demeaning to take orders from a woman boss or to
work under her leadership.
In most Caribbean territories, gender issues have been addressed. Although resistance still exists,
gender equality is advocated with respect to all occupations, including those which were
formerly thought of as exclusive to women, such as nursing, home economics, dressmaking, and
cosmetology. In the agricultural sector, jobs are advertised seeking persons who possess the
requisite qualifications, knowledge, skills, and experience, regardless of gender. Of course,
where heavy manual labour is concerned the employer is free to select the best person for the
particular job.
5. Discuss major current issues that could affect global agriculture
Globalisation has revolutionised agriculture. It is the process of increasing the connectivity and
interdependence of the world's markets and businesses. Globalisation offers farmers access to
world markets. Aircraft can now deliver fresh agricultural produce to the industrialised countries
from almost anywhere in the world in a single day. In addition to trading opportunities,
globalisation allows farmers to access information about new production techniques. Many
issues affect agriculture worldwide. Some of these also affect countries of the Caribbean and
they are outlined below.
Biodiversity
Biodiversity is the variation of life forms (plants and animals) on Earth and the many different
habitats (ecosystems) in which plants and animals live together. It is often used as a measure of
the health of biological systems. The biodiversity found on Earth today is made up of many
millions of biological species, the product of nearly 3.5 billion years of evolution.
Three levels of biodiversity have been identified:
• genetic diversity — the diversity of genes and organisms
• species diversity — the populations of organisms in an ecosystem
• ecosystem diversity — the range of habitats on Earth.
Natural vegetation, such as forest, is often cleared for agricultural purposes; this results in loss of
ecosystems with their associated plants and animals. There is worldwide concern about the loss
of natural ecosystems in the quest to increase food production and clear land for building. Loss
of biodiversity results from changes in terrestrial (land), marine and freshwater ecosystems.
Biodiversity also affects air quality, climate, and erosion. It is important for countries to conserve
biodiversity through public education and awareness.
Global warming
The Earth is surrounded by a blanket of air known as the atmosphere, which is made up of many
gases. Two of these, carbon dioxide and methane, are called greenhouse gases. In a greenhouse,
the glass roof and walls trap the heat energy of the sun and keep it within the greenhouse. A
warm temperature is maintained, and the enclosed plants thrive. Carbon dioxide and methane in
the atmosphere act rather like a greenhouse, producing what is known as the greenhouse effect.
When the sun's rays strike the Earth, some heat energy is absorbed, and some is radiated back
into space. The greenhouse gases in the atmosphere trap the energy and keep it in, warming the
air beneath and enabling all forms of life to survive. If this energy was not trapped, it would be
too cold to sustain life on Earth.
Within the last century, there has been an increase in the production of greenhouse gases due to
human activities. Increased industrialisation, motor transport, aeroplanes, the burning of garbage,
bush fires and deforestation all contribute to carbon dioxide in the atmosphere. This means that
more heat energy is trapped within the Earth's atmosphere, resulting in global warming.
Global warming can produce these effects:
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a rise in sea level, causing loss of coastal land areas and affecting agriculture, fishing and
community life
increased temperatures, which favour the growth of some crops but harm others
more drought, affecting water availability for both domestic and agricultural use
more hurricanes, which may have greater strength and cause havoc to crops and livestock
a rise in sea temperature, causing changes to coral reefs, fisheries and other marine
organisms
loss of habitats and diversity, with loss of plants and animals due to more stormy weather.
Bioterrorism
Bioterrorism is the intentional use of micro-organisms to bring about ill-effects or death to
humans, livestock, or crops. Agriculture is a perfect target for bioterrorism because an attack on
food supplies affects food stores, restaurants, suppliers, and consumers as well as farmers. All
countries need to be prepared for the possibility of an attack on crops, livestock, or humans.
Diseases useful to bioterrorists:
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Smallpox is a viral disease that can be fatal. In 1980, the disease was eradicated due to
worldwide vaccination programmes. Some stocks of the virus are kept in high-security
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laboratories. If smallpox is deliberately released, it could cause a public health
catastrophe.
Anthrax is a disease caused by a spore-forming bacterium called Bacillus anthracis. It is
caught by humans after contact with infected animals or infected animal products. It has
the potential to be used as a biological warfare agent.
Crop diseases, such as smuts and blights caused by fungi, can be spread easily by fungal
spores. If large areas of cereal crops are destroyed, less grain is produced.
Ricin is a toxin made from waste left over from processing castor beans. It is easily made
and very toxic. As little as 500 micrograms, about the size of the head of a pin, injected
into a human is lethal. Ricin has been used as a bioterrorist weapon and is a serious
threat.
Bioterrorism is hard to protect against or to prevent because small quantities of the organisms are
easy to hide and can be spread quickly. Sometimes pathogenic organisms can be spread by
mistake or by people unaware of the consequences. The rules which govern the import and
export of plants and animals are designed to protect against diseases being transported around the
world.
Food security
Food security refers to the availability of food and access to it. As defined by the FAO, 'food
security exists when people have physical and economic access to sufficient, safe and nutritious
food to meet their needs for an active and healthy life'. The United States Department of
Agriculture (USDA) states that food security for a household means access to enough food for an
active, healthy life. It includes the availability of nutritionally adequate and safe foods and an
ability to acquire these foods in socially acceptable ways (without resorting to emergency food
supplies, scavenging, or stealing).
Worldwide, up to 2 billion people lack food security due to:
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poverty
global population growth
climate change
increased production of biofuels on agricultural land
loss of agricultural land to industry and residential areas.
There are direct relationships between agricultural productivity, hunger, and poverty. 75% of the
world's poor live in rural areas and make their living from agriculture. Hunger and child
malnutrition are greater than in urban areas. In rural areas, there is greater dependence on
subsistence farming so improvements in agricultural productivity aimed at small-scale farmers
will benefit the rural poor first. Increased agricultural productivity enables farmers to grow more
food, which leads to better diets. Market conditions that offer a level playing field also lead to
higher farm incomes; and raised incomes often result in farmers growing higher value crops,
benefiting themselves and the economy.
Environmental degradation
Environmental degradation refers to the environment being damaged in any way.
Environmental degradation is brought about by:
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natural hazards
atmospheric pollution
water pollution
land pollution
global warming
coral reef destruction
deforestation
Natural hazards
Natural hazards are hazards which are not man-made. They occur at the surface of the Earth,
causing loss of life, damage to property and land. They can cause short-term or long-term
changes. The most common natural hazards in the Caribbean are volcanic eruptions, earthquakes,
floods, and hurricanes. Some of their effects are shown in Table 2.1.
Atmospheric pollution
Pollution occurs when the environment is contaminated by toxic substances. Atmospheric
pollution is pollution of the air. It is caused mainly by burning fossil fuels (often for the
generation of electricity). Smoke, dust particles and gases (carbon dioxide, sulphur dioxide,
nitrous oxides) are released. Sulphur dioxide is poisonous and dissolves in rainwater to form acid
rain, which damages crops. An increase in carbon dioxide contributes to global warming.
Atmospheric pollution is difficult to control, other than by reducing dependence on fossil fuels
and reducing 'carbon footprints'.
Water pollution
Water pollution describes toxic substances getting into streams, rivers, and oceans. Some of these
substances come from pollutants in the atmosphere. Others result from sewage, excessive use of
fertilisers and pesticide run-off. Organic matter and nutrients in freshwater can cause algae to
grow rapidly and crowd out other water plants. When the algae die, they are broken down by
bacteria which use up oxygen in the water. The result is that other aquatic organisms die through
lack of oxygen. In marine ecosystems, agricultural run-off can upset the food webs. Oil spillage
kills sea birds and affects plankton on which marine organisms are dependent.
Land pollution
Land pollution can be caused by agricultural activities, urban waste disposal and mineral
extraction. Land that is severely polluted cannot grow crops and poisonous substances will affect
the biodiversity of habitats. Waste from crops and animals should be composted and recycled for
use as fertiliser. Excessive use of fertilisers and pesticides should be discouraged, so that run-off
is minimised.
Coral reef destruction
Coral reefs are fragile ecosystems and easily damaged by pollution. Polluted water runs off the
land, enters the sea and increases the growth of algae which live on the reef. This kills the coral
underneath the algae. Corals can be smothered by sediments washed into the sea from rivers and
coastal dredging activities. Over-fishing and tourist activities upset the ecological balance so that
the physical structure of the reefs, as well as the plants and animals that live in them, suffer
damage. If sea temperatures rise, due to global warming, the coral is weakened and becomes
paler in colour. This is called coral bleaching. Weakened coral can be attacked by bacterial and
viral diseases. The invasion of coral reefs in the Caribbean by species such as the Indo-Pacific
lionfish could also alter the ecosystem.
Deforestation
For thousands of years, forests have been cleared to provide agricultural land for crop production
and rearing animals. The clearance of trees is known as deforestation. Five hundred years ago,
most of the Caribbean was covered in dense tropical forest. There are still many areas covered in
natural forest, but rising population means that there is pressure to clear land for crop production,
industry, and houses. Forests are cleared and wood is used for fuel, but there is no policy for
replanting trees. The forested areas that remain are in mountainous regions with high rainfall.
These are less accessible to the machinery needed to clear the land for farming. Natural hazards,
such as forest fires and tropical storms, also destroy forests. Hurricanes uproot forests and strip
leaves, leaving the trees bare. Volcanic activity, producing poisonous gases and hot lava, has
affected forests in Montserrat and St Vincent.
It is important to retain forests as they:
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provide areas for recreation, such as nature reserves and National Parks, with facilities for
hiking and other forms of relaxation
control soil erosion by providing cover to break up the force of the rain on the soil
absorb carbon dioxide and provide oxygen through photosynthesis
are an important source of timber for building and furniture.
Within protected areas of forest, replanting and maintenance work can be carried out to avoid
over-exploitation
6. Explain the terminology used in food safety, importation, and certification exercises
The procedures described in this section are used internationally to ensure that food is produced
and processed in a safe way. Good Agricultural Practices (GAPS) are applied to crop production
and animal husbandry, whereas HACCP and GMPs relate to the manufacture and processing of
food.
Good Agricultural Practices (GAPs)
As defined by the Food and Agriculture Organisation (FAO) of the United Nations, GAPs are
principles applied to crop production and processing, which result in safe and healthy food,
considering economic, social and environmental sustainability.
GAPs can be applied to a wide range of farming systems and rely on four principles:
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the economic and efficient production of enough safe and nutritious food
sustaining natural resources
maintaining farming enterprises and jobs
meeting the cultural and social demands of society.
GAPs provide opportunities to decide which farming practices to follow to achieve higher
production.
Some GAPs relate to soil:
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reduction of erosion by hedging and ditching
the correct application of fertilisers
the use of manure, grazing and crop rotation in restoring and maintaining the organic
content of the soil
green manuring by growing leguminous crops
protection of soil structure by limiting use of heavy machinery (this compacts the soil).
Some GAPs relate to water:
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careful use of irrigation
avoiding drainage and fertiliser run-off
planting of suitable crops in areas of low rainfall
maintaining plant cover to avoid water run-off in the wet season.
Some GAPs relate to animal production, health, and welfare:
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respect for animals
avoidance of procedures such as tail docking and de-beaking
reducing use of antibiotics and hormones unless needed for treatment of disease
avoidance of animal waste in any feed given to stock
reducing the transport of live animals, thus cutting down on the risks of epidemics
keeping records so that all animals and their treatments can be traced.
Hazard Analysis Critical Control Point (HACCP)
HACCP is a systematic approach to food safety used to identify potential hazards in the food
industry. It is used at all stages of food production and preparation, particularly the production of
juice, seafood, meat, and poultry products. It ensures that food is fit for human consumption by
monitoring the stages in its production.
There are seven HACCP principles:
1. Conduct a hazard analysis to identify measures that can be taken to control any
biological, chemical, or physical hazard that could cause food to be unsafe for human
consumption.
2. Identify Critical Control Points (CCPs) in a food manufacturing process at which a
hazard can be prevented, removed, or reduced.
3. Establish critical limits for each critical control point. A critical limit sets a value at which
a hazard must be controlled at each point.
4. Establish critical control point monitoring requirements to ensure that the manufacturing
process is under control.
5. Establish corrective actions to be taken when the monitoring process indicates that a
critical limit is not being met — this means that products harmful to health do not
become available for human consumption.
6. Establish record-keeping procedures so that it can be seen that all steps of the process
have been monitored for hazards.
7. Establish procedures for ensuring that the HACCP system is working as it should and that
the products from any manufacturing process are safe.
Food processing plants must ensure that their products are safe. They are required to validate
their own HACCP plans, which have to be verified to make sure that they are adequate.
Verification includes reviewing of plans, inspection of critical control point records and
microbial sampling.
Good Manufacturing Practices (GMPs)
GMPs regulate the manufacture and testing of food products, drugs, and medicines. Every aspect
of a process is documented so that products can be traced and recalled if unsatisfactory. GMPs
are particularly important in the manufacture of pharmaceutical products (medicines). GMPs in
the food industry identify and prevent the contamination of raw materials. They also deal with
poor design of processing plants and procedures and deficiencies in training employees.
Refrigerated foods, meat and dairy foods have a high risk of safety problems as they may
become contaminated with pathogens. Another problem is that allergens may be introduced into
foods (some people, for example, are allergic to nuts). Food safety experts recommend that
training of employees is important in maintaining quality control of materials, adequate cleaning
of equipment and documentation of procedures. GMPs, together with HACCP, ensure that
manufactured food products are fit for human consumption.
Alternative to Conventional Farming
7. Explain the importance of non-conventional farming systems
Modern farming methods
By conventional farming methods we mean modem farming methods, which are designed to
produce large quantities of food to be sold for profit. Farming is now a large-scale industry and
relies on the use of machinery and chemicals. Few people are required to operate the machinery,
which prepares the land, sows the seeds and harvests the crops. This trend in farming has
occurred in response to increasing populations and the demand for cheaper food. Monoculture,
where large areas of land are planted with the same crop year after year, is a feature of modem
farming. It often leads to greater farm profits as a much greater quantity of a crop can be grown.
However, monoculture also leads to loss of natural ecosystems and habitats. Modem farming
relies on artificial fertilisers to improve soil fertility and increase crop yields. Diseases are
prevented by pesticides; weeds are destroyed by herbicides and chemicals are fed to animals to
promote growth. However, there is now concern that modem agricultural practices damage the
environment and soil structure, reduce biodiversity and introduce health hazards to both humans
and animals.
Traditional farming methods
In contrast to modern fanning, traditional methods of agriculture cause less damage to the
environment. An example of traditional fanning is small-scale mixed farming, where there is
recycling of waste materials. The waste from animals is used as manure, so nutrients are returned
to the soil via the carbon and nitrogen cycles. By growing a wide range of crops and using crop
rotation, both soil structure and fertility can be maintained. Traditional farming methods are
more sustainable than modem methods.
Non-conventional farming systems
Non-conventional farming systems have developed in response to concerns about the effects of
intensive systems on the environment and the quality of food produced. Most non-conventional
systems are labour-intensive (they employ more people than conventional systems). Also, yields
are lower than in conventional systems. However, the food produced by non-conventional
farming is likely to be of better quality and so command a higher market price.
Organic farming
Organic farming is a form of non-conventional agriculture that excludes, or strictly limits, the
use of artificial fertilisers, herbicides and pesticides, plant growth regulators and animal feed
additives. Biological pest control is used instead to get rid of pests. Compost, green manure and
crop rotation are used to maintain soil fertility. Techniques may vary from country to country, but
the principles and practices were set out in a document produced by the International Federation
of Organic Agricultural Movements (IFOAM). In 2005, this organisation created the Principles
of Organic Agriculture as guidelines for the certification of organic farms.
Organic farmers need to develop a fertile soil on which they grow a mixture of crops. They
cannot use artificial fertilisers and use of pesticides is restricted. They rear animals in a humane
way, without routine use of the hormones and antibiotics that are common in intensive livestock
production. They are not allowed to grow genetically modified crops.
Hydroponics
Hydroponics (from the Greek words hydros [water] and ponos [labour]) is the practice of
growing plants in a nutrient solution without soil. This is another form of non-conventional
farming. Instead of soil, the plants may be rooted in peat, sand, or rock wool. Soil is not essential
for the growth of terrestrial plants (plants that grow on land), as roots can absorb all the mineral
ions needed for growth from a nutrient solution. Hydroponics can supply fruit and vegetables in
areas where the soil is lacking or of poor quality. The commercial use of hydroponics was
demonstrated on Wake Island in the Pacific. In the 1930s, this rocky atoll was a refuelling stop
for an airline. As there was no soil, vegetables for the passengers were grown in nutrient
solutions. Space research programmes have also looked into growing plants on other planets or
during long flights.
The nutrient film technique
In the 1960s, the nutrient film technique (NFT) was developed. A circulating system supplies
plant roots with oxygen and nutrients. This technique is widely used for growing tomatoes,
cucumbers and salad vegetables in glasshouses. The plants are grown in troughs, with roots
embedded in rock wool or some other inert material. They are supplied with a nutrient solution
containing the balance of minerals essential for healthy growth. The solution is pumped into the
troughs, circulates around the roots, collects in a tank and is then re-circulated.
Concentration of the nutrient solution can be varied at different stages of growth as required. The
solution is aerated so that roots obtain oxygen. As plants grout, they are supported by wires
suspended from the roof of the glasshouse.
The advantages of the nutrient film technique are:
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high yields as plants get all the nutrients they require
soil-borne diseases are eliminated
produce is clean and not covered in soil
harvesting the produce is easier and more efficient.
The nutrient film technique is usually carried out in glasshouses, where temperature and light can
be controlled. Costs of installing and running this are high, but producing fruit and vegetables in
large quantities and of good quality out of season can make this technique profitable.
Grow boxes
A grow box is an enclosed box used to grow plants in a self-contained environment. The box has
a hydroponics system, a built-in light and a means of ventilation. Some have air-conditioning to
maintain the correct temperature and to enrich the atmosphere with carbon dioxide to boost
growth (carbon dioxide makes plants grow faster).
Grow boxes are used by people who have no garden and for growing plants out of season. They
are easy to use and allow the gardener to control the environment of the plant to achieve the best
growth. They are also used for growing plants in controlled conditions in laboratories. Simplified
grow boxes, suitable for patios and decking, have been devised. These incorporate a watering
system and deliver measured quantities of fertiliser, but they are designed for use outdoors and
do not include a lighting system or temperature control.
In the Caribbean, grow boxes of varying sizes are constructed using local and discarded
materials such as bamboo, wood, galvanised sheets, and bricks. The growing medium may be a
mixture of topsoil and pen manure, sharp sand and rotted bagasse (or plastering sand and rotted
sawdust).
Trough culture
Trough culture involves growing crops in shallow troughs, 15-20 cm deep and 60-70 cm wide.
Troughs can be filled with an inert, soil-less medium, such as rock wool, and are connected to a
drip system which supplies water and nutrients in solution. Once the troughs have been set up,
they are easy and inexpensive to maintain. They can be used for vegetables and flowers; the
gardener can put them in greenhouses or anywhere convenient. Both grow boxes and trough
culture enable plants to be grown where space is limited, or soil is poor. Modifications can be
made to suit circumstances, e.g., the number of units and their arrangement; the use of different
types of inert material; whether temperature and lighting need to be controlled. Commercial
systems have many units, but both methods can be used on a smaller scale.
Urban and peri-urban farming
Urban and peri-urban farming is the cultivation of small areas of land, usually less than 2
hectares, in or near cities, towns and villages. The small farms, or market gardens as they are
sometimes called, produce fresh vegetables, fruit, and meat for urban consumers. These benefit
the community by increasing the quantity and quality of the food available. They contribute to
food safety and food security.
Market gardens are intensively cultivated, and most crops grown are short-term, growing and
ripening within 3 months. Crops include tomatoes, lettuces, cucumbers, cabbages, Pak-choi,
celery, sweet peppers, and spinach. Sometimes four short-term crops are grown in a year, so
fertilisers are used to maintain soil fertility. If the small farm is mixed, with some animals being
kept, then farmyard manure is used together with artificial fertilisers. This type of farming
includes the use of pots, troughs, grow boxes, discarded tyres, hydroponics, and sheds covered
with polythene.
Produce is harvested by the farmer, often with the help of his family, who also get it ready for
market. Vegetables are cleaned, graded, and made to look presentable to the consumer. If the
farm is very small, the farmer will sell from a roadside stall. If the farm is bigger, the farmer will
sell to a wholesaler, who buys the whole crop and transports it to a market where it is sold to
retailers. Each time produce is sold, e.g., from farmer to wholesaler and from wholesaler to
retailer, the price increases.
Urban farms are important to the economy of the Caribbean region. Several Caribbean
governments have set up marketing boards to purchase crops from urban farmers and retail them
to the public.
The benefits of urban farms include:
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a reduction in transport costs as food is grown locally
fewer pesticides, which make food production more sustainable
no food preservatives as food does not have to travel long distances
employment for local people.
8. Explain the principles that govern organic farming
In organic farming, the use of herbicides and pesticides is limited resulting in an increase in
biodiversity. Organic farming benefits the environment in many ways. Weed species growing in
an organic crop attract insects which feed on plant pests. In turn, these insects will provide food
for birds and mammals. The use of farmyard manure to add organic matter to the soil encourages
soil micro-organisms, which contribute to soil fertility by breaking down plant and animal
remains. Overall, there are 30% more species found on organic farms than on conventional
farms. Organically grown produce is usually higher priced than other produce — but healthconscious people will often pay these prices.
Soil management on organic farms
An organic farmer uses soil management to ensure a supply of the essential nutrients (nitrogen,
potassium, and phosphorus). Instead of relying on artificial fertilisers, the farmer can use some of
the methods summarised in Table 3.1.
Weed control on organic farms
Weed control on organic farms poses problems as herbicides are not encouraged. Methods
include hand-weeding, hoeing, mulching with compost and the use of plastic films spread across
the ground. In rice-growing areas, ducks and fish have been introduced to paddy fields to eat
weeds and insects.
Pest control on organic farms
The control of insects and other pests is difficult to achieve without chemicals. Pests cause
serious losses, and few organic farmers manage to eliminate the use of chemical pesticides
entirely. Organic insecticides include Bt (a bacterial toxin produced by Bacillus thuringiensis),
Pyrethrum and Rotenone. Although these are permitted, they are often combined with biological
pest control and cultural methods in a technique called integrated pest management (IPM). IPM
involves pest control using an array of complementary approaches including natural predators,
pesticides, and other biological and environmental control practices. In this way, the use of
chemicals is reduced and damage to the environment and harmful residues in food are
minimised.
Biological pest control involves the introduction of another species to control the pest. The
introduced species will reduce the population of the pest but will not get rid of it completely.
The introduced species may be:
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a natural predator of the pest organism, such as a mite
a parasitoid, such as a wasp that lays its eggs in another insect
a parasite, such as a nematode worm that lives in slugs
a pathogenic (disease-causing) organism, such as a bacterium.
Before any biological control method is used, it has to be tested to make sure that no unwanted
diseases are introduced, that it only affects the pest organism, and that the control organism can
be bred in sufficient numbers to be effective. Biological control is most successful in glasshouse
crops, such as tomatoes and cucumbers. The control organisms are introduced into the
glasshouse (an enclosed area), and numbers of pest and predator can be carefully monitored.
If the life cycle of an insect pest is interrupted, its numbers will fall. Insects mate once and the
female stores the sperm. If the sperm are infertile, fewer offspring will be produced. It is possible
to sterilise male insects using ionising radiation (X-rays) and then allow them to mate with
normal females. The sperm will be defective, and the eggs laid by the females do not develop.
This method has been effective in the control of screwworms which harmed the cattle industry in
the USA.
Alternative control methods involve the use of chemicals and hormones to lure insects to
positions where they can be killed by other methods. Hormones from female insects attract the
males. If traps are baited with these hormones, the males can be caught and destroyed. If there
are no males for the females to mate with, no eggs will be laid, and the pests will be reduced.
Certification of organic farms
Farmers who sell their produce as 'organic' must obtain certification.
There are some basic steps to the certification procedure:
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the farmer finds a suitable agency that will carry out the procedure
the farmer makes an application (it is usually necessary to pay a fee at this stage)
the farm has to be inspected by the agency
the farmer will be notified whether or not the application is successful.
The application form requires details of:
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soil fertility planning
seeds and seed planting
weed and pest management practices
storage and handling of produce
details of the crops grown, and the fields used (a map of the farm has to be supplied)
plans for monitoring how the farm will be managed to avoid contamination with nonorganic products.
When the farm is inspected, the fields, implements and buildings are reviewed. The farmer
provides the inspector with records of crops planted, sources of seeds used, details of harvesting
and storage, how the produce is transported to market, and the sales records. Before a certificate
can be granted, land has to be free from prohibited pesticides and fertilisers for 3 years. If
livestock are involved, the conditions in which they are kept, their feed and medication have to
be inspected.
The inspectors have to be convinced that the producer uses techniques that conserve and build
soil resources, produce little pollution, and support natural pest management. In addition, the
inspectors make sure that there is no contamination from pesticides and fertilisers used on
neighbouring farms.
Becoming 'organic' can be expensive and time-consuming for a small farmer. There is usually a
fee to be paid for inspection and certification, and much record-keeping and paperwork.
However, the principles of organic farming encourage the maintenance of ecological balance and
biodiversity. Many consumers are prepared to pay more for organically produced food.
Economic Factors of Production
9. Define the economic functions of production, consumption, and marketing
Farming is a business, and a farm can be defined as an economic unit engaged in the production
and sale of agricultural produce for maximum profit. A farm may produce crops or livestock.
Sometimes farms produce both crops and livestock (a mixed farm).
Farms often consist of different sections, each focused on the production of one type of crop or
livestock. Each section of a farm is known as an agricultural enterprise. The farmer manages
each enterprise by deciding how much to produce and how to allocate resources to obtain high
yields and maximum profit. To do this, knowledge of the production process is necessary. The
farmer also must understand the likely demand for the commodity and the way in which it is
marketed.
In any country, the economy is the vehicle of change and development. There are three major
parts of this vehicle: production, consumption, and marketing. Each part carries out specific
functions.
Production plays the role of the engine of the economy, marketing has the role of the driver, and
consumption provides the fuel.
Production
Production is a planned economic activity incorporating several inputs; it focuses on the
manufacture of goods and the provision of a number of services. The aim of production is to
satisfy people's wants. As the volume of production increases, wealth is created, and this
promotes economic welfare of the population. Their standard of living is improved as more of
their wants are satisfied.
Types of production
There are two types of production: primary and secondary. Primary production refers to goods or
raw materials which are produced initially, for example pineapple or sugar cane. Some of these
goods may be consumed as primary products. Alternatively, primary products may undergo
secondary production, which involves processing the raw products into secondary products. For
example, pineapple may be processed into jam and juice, or sugar cane can be processed to make
sugar, molasses, bagasse, and rum.
Goods
Different kinds of goods are derived from production. Capital goods are items such as a farm
tractor and a dairy herd — these are used in several production cycles. There is always a quantity
of goods existing on a farm and this is called the capital. Luxury goods, such as a swimming pool
and a big screen television set, provide enjoyment and act as status symbols. Consumable goods,
such as foodstuffs, are goods which are essential for human nutrition.
Services
Services can be grouped into:
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commercial services, such as those provided by agri-supply stores and livestock depots
technical services, such as those provided by extension officers and agri-teachers
professional services, such as those provided by agricultural consultants and
veterinarians.
Consumption
Consumption is an economic, consumer-centred activity. It involves the purchase and use of
goods and services by clients and customers (known as consumers). Consumption normally
comes after production and marketing and is the fuel which keeps the economic engine of
production running.
Consumption patterns vary. Some factors which contribute to decision-making by consumers are:
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Income level
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Consumers want to obtain goods and services at the lowest cost. They purchase and use
those goods and services which they can afford. People on low incomes are limited in
terms of the quantity and the form of product which they can purchase.
Satisfaction of needs
Consumers choose goods and services which satisfy their tastes and convenience. With
respect to food, consumers buy products which are easy to prepare and use, and which
meet their survival, nutritional and health needs.
Religious reasons
Some consumers do not buy certain foods, such as pork and beef, due to religious beliefs.
Others buy only 'halal' meat from reputable meat shops. 'Halal' involves the reciting of a
special prayer by Muslims as the animal is being slaughtered.
Health concerns
More consumers are becoming health-conscious and avoid buying foods which contain
high amounts of cholesterol and saturated fats.
Aesthetic features
Product features (design, presentation, colour, taste and general appearance) appeal to
consumers, increasing consumption of those products.
Product substitutes
Knowledge of product substitutes and their availability might enable some, consumers to
make compromises and choose alternative goods and services.
Marketing
Marketing is the link between production and consumption. It incorporates several business
activities in a co-ordinated way to promote the flow of goods and services from the point of
production until they finally reach the consumer. The process is streamlined to get the right
product to a particular consumer at the right place and time. This is achieved by the co-operative
effort of each business operator in the marketing channel.
Middlemen operate between the producers and consumers. They are agents, brokers, wholesalers
(merchants), processors and retailers (vendors).
The merchant wholesalers purchase and collect products together at a focal point for distribution
to processors and retailers. Often this is accomplished through the services of commission agents
and brokers, who are also acting as salespersons. Huge sums of money are spent in advertising
and product promotion to persuade consumers to purchase and use new products.
Marketing functions (see Table 4.1) vary in complexity, depending on the nature of the products,
quantity produced and the characteristics of the market.
10. State the factors of production
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Land
Labour - to carry out the tasks
Capital - is needed to finance any manufacturing process
Management structure is necessary to co-ordinate the activities
The essential resource is the one from which the product is derived. In the case of agricultural
production, land is an essential resource (see Figure 4.4).
Agricultural production varies with the amount, quality, and effective use of these essential
resources: land, labour, capital and management. These resources are known as the factors of
production.
11. Relate the factors of production to agriculture
Land
The Caribbean region is dominated by small island states with little flat or undulating land and
there are numerous smallholdings on hilly terrain. Only Guyana and Belize have large expanses
of flat land suitable for large-scale agricultural development. Unfortunately, those areas are
currently under-used. Despite land reclamation initiatives in some Caribbean countries, land as a
factor of production is a limited resource which cannot be created. Farmers may work on land
which is rented or leased. Many do not own land and enter into sharecropping arrangements with
their landlords. Sharecropping is a system of agriculture or agricultural production in which a
landowner allows a tenant to use the land in return for a share of the crop produced on the land.
Often sharecropping farmers may farm two or more scattered holdings. Land tenure systems
were described in Chapter 2. The suitability of the land for agricultural production depends on
both climate and topography. The climate, with its seasonal variations in rainfall and
temperature, affects the types of crops that can be grown; whereas the topography affects the
ease of cultivation and equipment that can be used (see Chapter 2).
Loss of agricultural land
Land often appreciates (rises) in value over time and can make large profits for residential
developers who sell the land for housing. Governments also acquire land in prime agricultural
areas for housing schemes. Over-cultivation and a loss of soil fertility also mean that less
agricultural land is available. If agricultural productivity is to be maintained or increased, land
needs to be managed and used effectively. Therefore, farmers should adopt suitable soil
management techniques, cultural practices and take advantage of improved technology. In this
way, soil fertility and agricultural land can be maintained.
Labour
Labour is the total sum of money (the cost) and the total number of man-hours required for the
production of commodities.
In the Caribbean, labour has been a challenging factor of production in commercial farming, both
locally and regionally. Slavery and indentureship, instituted by the former plantocracy, have
resulted in a negative attitude towards agriculture labour. III-treatment of the slaves resulted in
their descendants pursuing other careers rather than working on the land.
Farmers with smallholdings largely rely on self-labour and family labour (the work is done by
the family). The cost of such labour is not considered as a part of the general cost of production,
as no money is actually paid out for the work done.
Casual labour
Farmers who operate medium-scale and large-scale farms use hired labour on a permanent basis
and casual labour (temporary paid labour) for specific farm operations.
Casual labour may be:
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seasonal labour at peak periods for planting, harvesting, fertiliser applications or pest and
disease control
task labour for specified hours of work and operations such as procuring forage and
milking cows
contract labour for infrastructural works, such as the construction of livestock pens and
land preparation.
In Trinidad and Tobago, the minimum wage policy of the government has increased the income
of farm workers but has not resulted in attracting workers into the private agricultural sector.
People would rather work for the government unemployment relief programmes where hours of
work and tasks are less demanding. The wages and conditions are also better.
The intervention of local and regional governments, as well as the International Labour
Organisation (ILO), is required to:
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develop a system of wages based on specialised agricultural skills which would attract
workers to the agricultural sector
institute measures to foster better labour relations
promote the welfare of farm workers and their families, especially in the private
agricultural sector.
Capital
Capital refers to all buildings, machinery, equipment, tools, materials, tree crops and livestock
which are used to produce agricultural goods and services on a continuing basis.
Each resource has a productive lifespan and a monetary value that decreases with time due to
depreciation. Depreciation is a decrease in value due to age or wear. Farmers need to ensure that
regular maintenance is carried out to keep each resource in a serviceable condition. Collectively,
capital resources and land are referred to as assets and are expressed in monetary terms as
wealth.
Loans
If a farmer needs to finance an agricultural enterprise and has no money from family resources,
he may seek a low interest loan. The farmer may have to offer capital resources, or assets, as
collateral to the lending institution. In this way, capital enables the farmer to become self-reliant.
It is easier for farmers with large farms to borrow money than it is for farmers with small farms.
The larger the farm, the greater the assets; this means that profits will be greater, and the farmer
can repay the loan more quickly.
Loans can be obtained from:
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commercial banks
agricultural banks
co-operatives
credit unions.
Some commercial banks have agricultural advisers who understand the problems of farming and
can give advice. Usually, these banks only make loans to big farms. Commercial banks do not
like lending to small farmers, particularly as their profits can be badly affected by a bad harvest,
hurricanes, and other disasters. The small farmer is not a good risk and may not be able to repay
the loan promptly.
The Caribbean Development Bank (CDB) is committed to financing projects in the region and
has departments that loan money to farmers. It prefers long-term loans and is prepared to allow a
longer repayment time.
In the case of co-operatives (see page 72), several farmers working together can apply for a loan.
A bank is likely to look more favourably at such applications.
A credit union is a co-operative financial institution that is owned and controlled by its members.
It is different from a conventional bank in that members who have accounts in the credit union
collectively own the credit union. It offers facilities for. savings accounts, as well as for
borrowing money at reasonable rates of interest.
The Caribbean Confederation of Credit Unions is an organisation that fosters co-operation and
mutual self-help. Funds help a variety of projects including rural development. There is provision
for funding small businesses and small farmers. Jamaica, for example, has 56 credit unions with
assets of millions of dollars.
Sources of capital
In the Caribbean, farmers may obtain capital, that is money (cash) and/or a stock of agricultural
materials, from the following sources:
1. Government institutions
Agricultural Development Bank These include the (ADB), the Ministry of Agriculture
and agricultural societies. The ADB and the agricultural societies offer loans at low rates
of interest, usually from 3% to 6%. The Ministry of Agriculture arranges subsidised farm
inputs (machinery, equipment, breeding stock, starter colonies of bees, hybrid seeds and
other planting mate rials). They also arrange leases for state land.
2. Commercial banks/Enterprises and insurance companies
The rates of interest from commercial banks, insurance companies and financial agencies
are higher than those from the government institutions (8% to 14%). The commercial
enterprises sell land, planting mate rials, machinery and equipment.
3. Credit Unions
These offer loans at low rates of interest.
4. Co-operatives and Associations
These organisations rent out machinery and equipment and offer loans at low rates of
interest. Depending on the nature of the co-operative or association, planting materials,
breeding stock and starter colonies of bees may be offered.
5. Sou-Sou Groups
In these friendly co-operative savings schemes, each person in a small group contributes
every week or month, as agreed, an equal portion of money. The sum of the group's total
contribution goes to one member of the group in rotation, so that every month, week or
fortnight one person benefits from a large sum of money, interest-free, that can be put to a
particular use. In Dominica the practice is more often called a 'sub'. This system was
more widespread before banks openly welcomed small-scale savers and before the Credit
Union movement established itself in the 1950s and 1960s.
6. Moneylenders
Loans from moneylenders have high rates of interest and relatively short repayment
times.
7. Personal savings
The farmer may have saved money over a period of time from the profits of the farm
8. Relatives
This may take the form of a loan, at a reasonable rate of interest, borrowed machinery
and equipment, or an inheritance of land, cash, buildings or machinery and equipment.
9. Friends
Friends may offer loans at reasonable rates of interest, or land, machinery, tree crops and
livestock might be borrowed in a share-cropping arrangement.
Fixed and working capital
Fixed capital is the amount of capital permanently invested in a business. It refers to assets that
are not used up in the production of a product. It is the capital that is invested in land, buildings,
vehicles, and equipment. Working capital refers to the assets of a business that are used to
convert raw materials into a product. For a farmer, the working capital consists of labour costs,
cost of seed or stock, means of getting the product to market, and the cash received for goods.
The farmer keeps accounts of expenditure on labour, seeds and hire of equipment and the
receipts for the produce that is sold. He can then see whether or not there is a profit, which can
be invested to improve the enterprise.
Management
Management focuses on the effective use of resources by the farmer. These resources include
land, labour, materials, finances and time. The farmer needs to achieve maximum production at
minimum cost. If used wisely, management can sustain agricultural output and quality.
On small-sized and medium-sized holdings, most farmers act as their own farm managers. They
carry out the functions of planning, organising and directing the workers and supervising farm
operations. On large farms, farm managers are employed to carry out these tasks. A farm
manager may be responsible for running a single enterprise or have overall responsibility for
day-to-day operations on the farm.
Management involves situational analysis, decision-making and the acceptance of full
responsibility for the outcomes, whether they are positive or negative. It requires people who
have gained technical knowledge of the scientific principles of agriculture, and who can combine
practical farming skills with business experience. A good farm manager has a grasp of the factors
of production and uses resources effectively to make a profit.
12. Explain the law of diminishing returns
The 'law of diminishing returns' states that if inputs are fixed and increasing amounts of just one
variable input are added, then the marginal output per unit of the variable input will increase up
to a certain point and then decline. Another name for marginal output is marginal return. To
understand how this law works, we need to understand the terms used.
Input
Input is something that is 'put into' a production system for a particular purpose and which
contributes to the end result. Inputs include energy, information, data programmes and supplies.
In a farming enterprise, inputs consist of:
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land
labour
machinery
fuel
farm buildings
planting materials
fertilisers and pesticides.
In agricultural production, inputs such as land, machinery, equipment, and farm buildings do not
change and are referred to as fixed inputs. The quantities of other inputs, such as labour, fuel,
stock, and maintenance of equipment may change; these are referred to as variable inputs.
Costs
Costs are the expenses involved in any transaction. Farmers have to buy farm inputs and convert
them into products. Costs that do not change, such as land rental, machinery, and buildings, are
referred to as fixed costs. Variable costs are those costs which change with the level of
production. These include the cost of fuel, feed, fertilisers, and pesticides. Obviously, if a farmer
decides to increase the number of broiler chicks, then more feed will be needed (see Table 4.2).
Output
The output is the quantity of product resulting from a production process. It can also be called
the yield or the return. The output may be expressed in metric tonnes (sugar cane), kilograms
(sweet potatoes) or simply numbers of products such as lettuce or eggs. In economics, output is
always measured in units. One unit could be 100 kg of sweet potatoes or 1000 table eggs.
The production of further units of output would require a greater amount of inputs, which would
increase the total cost to the farmer. Since most farmers operate with limited resources, they are
limited in the maximum number of units of output they can produce. For example, a farmer
would need to cultivate extra land, employ more labour and spend more on fertilisers if extra
units of sweet potatoes were to be produced.
The costs associated with output are:
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fixed costs (FC)
variable costs (VC)
total cost (TC)
average cost (AC)
marginal cost (MC).
As can be seen in Table 4.3, at any level of output:
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total cost (TC) is fixed cost (FC) plus variable cost (VC)
average cost (AC) is total cost (TC) divided by the number of units of output
marginal cost (MC) is the increase in total cost (TC) which is derived from the last unit of
commodity that is produced.
Returns
Farmers put their inputs into agricultural enterprises with the aim of making a profit. The yields
of the crop or the profits made are called the returns. If a particular input is increased, unit by
unit, there is an incremental increase in output up to a point. After this point, any further increase
in input does not increase the rate of output. The rate of increase of output declines with each
additional unit of input (see page 47 for the 'law of diminishing returns').
For example, in producing one ha of sweet potatoes, a farmer may gradually increase the units of
fertiliser (input) and find that his yield (output) has also increased progressively up to a
maximum point. After this point, continued increase in the units of fertiliser results in a steady
decline in output. These features are referred to as increasing returns when the output increases;
and diminishing returns as the output declines. Table 4.4 demonstrates this principle. Figure 4.5
shows the data in Table 4.4 plotted on a graph.
Increasing returns mean that each additional unit of input increases total outputs successively.
The successive increase in total output for each additional unit of input is called marginal output,
marginal return, marginal product or marginal yield (these all mean the same). Decreasing
returns mean that each additional unit of input increases total output at a declining rate. This
declining rate of increase in total output, resulting from each successive unit of input, is called a
diminishing return. The 'law of diminishing returns' is also known as the 'law of diminishing
marginal returns' and also as the 'law of marginal proportions'.
In Table 4.5, the fixed input is the land, the variable input is the quantity of fertiliser, and the
output or product is corn. Total output is total yield or total product. Average output (average
yield or average product) is calculated by dividing total output by the number of units of fertiliser
applied at any level of production. Marginal output (marginal yield or marginal product) is the
increase in total output which results from increasing the variable input by one unit. For
example, if 6 units of fertiliser are applied, total output is 2800 kg of corn, average output is 470
kg of corn and the marginal output is 300 kg of corn.
The total product curve
Figure 4.6 shows the relationship between the variable input and the total output. This is called
the total product curve. It rises sharply and then levels off before declining. The output increases
first at an increasing rate, then at a decreasing rate to a maximum level and then declines. The
maximum rate is reached at D, where the marginal product curve reaches 0. The declining rate of
increase starts at A where the marginal product is at its maximum.
Average product curve
The average product curve is obtained from the total product divided by the number, of units of
variable input, so the shape of the curve depends on the shape of the total product curve. The
maximum is reached at C where the average product is equal to the marginal product.
Marginal product curve
The marginal product curve increases very sharply in the beginning, reaches a maximum and
then declines. When the average product is at a maximum (C), then the marginal product is equal
to the average product. The marginal product becomes 0 (E) when the total product curve is at
the maximum (D).
The three stages
Look at Figure 4.6. In Stage 1, the total product is increasing sharply, and the point is reached
where average product equals marginal product. In Stage 2, both average product and marginal
product are declining although total product is still increasing, but at a decreasing rate. Stage 3
represents the inefficient stage of production as total product and average product decrease, and
marginal product shows negative values. It is costly to increase the variable input beyond the
point where the total product is at its maximum.
Relevance and application
The 'law of diminishing returns' is of relevance to farmers and horticulturalists. Producers need
to remember that there is increasing growth and development in crops and animals up to a
maximum point, beyond which diminishing returns set in. In producing broilers, for example,
diminishing returns become evident after 8 weeks when they have reached an average weight of
2 kg. From this time onwards, the birds consume an enormous quantity of feed but the rate of
increase in their body weight declines. Therefore, feed is wasted if they are kept until they reach
3.5 kg.
In the case of crops, there may be wastage of fertilisers, organic manure, pesticides and labour if
variable inputs do not result in the maximum marginal product. Such resources could be used
more profitably to produce other short-term crops or to raise a new batch of early maturing
animals.
13. Relate demand and supply to pricing.
Sellers mark their goods at a specific price or price range to dispose of their stock. In this way,
they hope to make a profit, enabling them to continue their business and perhaps expand it. If the
price of the goods is not controlled by the government, the seller is free to fix a price based on
market intelligence, the business location, and the total cost involved in buying and transporting
the goods to the place of business.
The willingness of the consumer to buy goods depends on the price as well as the supply. If the
price is too high, sales are poor because of low demand. If the price is too low, demand will be
high. The seller will be able to sell all his goods, but his profit may be very small, and this could
affect his business. Obviously, for any commodity, there is an optimum price which consumers
will be willing to pay and at which the seller may sell all his goods. This optimum price requires
decision-making on the part of the seller. The decision is based on the strength of demand from
prospective buyers and a guarantee of a regular supply of goods.
Demand
Demand is the quantity of a product which consumers are willing to buy at a certain price at a
particular time. Demand is directly related to price. If the price is high, demand will be low.
Lowering the price will result in an increase in demand for the product.
The demand schedules
The demand schedule for a product is the sum of all the individual consumers' demands,
tabulated to show the relationship between the quantity of the product demanded at various
prices. The demand schedule is also known as the market demand schedule and the prices are
called demand prices. The information in Table 4.6 can be shown graphically (see Figure 4.7).
In Figure 4.8, the curve DD shows at a glance the relationship between price and the quantity
bought. It is not necessary to have actual prices and quantities marked on the axes. You can see
that prices and quantity increase evenly from 0 to Y and from 0 to X respectively and that the
typical demand curve DD slopes downward from left to right.
The `law of demand'
The first law of supply and demand is also called the 'law of demand'. It states that the lower the
price, the greater the quantity that will be demanded.
Change in demand
In Figure 4.9, the demand curve DD represents the same conditions of demand at a certain time.
Generally, a change in demand results in a new demand curve which represents new conditions
of demand and time.
In Figure 4.9, the original state of demand is represented by curve DD. The price is OP and the
quantity demanded is OQ. If there is a change in demand, represented b' then at the old price of
OP the quantity now demanded is OQ1. This quantity is smaller than the former quantity.
Similarly, a change of demand represented bi the demand curve D2D2 shows that at the same
price of OP, a larger quantity of OQ is demanded.
Factors affecting change in demand
Some of the factors bringing about a change in demand are:
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change in tastes and preferences
change in income
replacement of old products with new ones (technical innovations)
change in the prices of other commodities
change in population • future trade expectations
taxes and duties
advertising the product.
Supply
Supply is the quantity of a commodity that is placed on the market at a particular time and at a
certain price. This supply does not include the entire stock, but only the amount that is brought
on to the market at the prevailing price and time. As with demand, the supply of a product is
directly related to the price of that product. Obviously, sellers want to release a larger amount of
a product on the market when the price is at a high level.
The supply schedule
The supply schedule for a commodity is the grand total of all the amounts of the individual
sellers, tabulated to show the relationship between the quantity offered for sale at different
prices. This is also known as the market supply schedule and the prices in the schedule are called
supply prices. A supply curve (Figure 4.10) can be plotted using the data in Table 4.7.
The 'law of supply'
The second law of supply and demand, also called the 'law of supply', states that the higher the
price, the greater the quantity that will be supplied.
Changes in supply
As with demand, a change in supply results in a new supply curve (Figure 4.12) which represents
new conditions of supply and time.
In Figure 4.12, the initial state of supply is represented by the curve SS, the price is OP and the
quantity supplied is OQ. If some factor causes the supply to change, the new conditions of
supply are represented by S,S,, which is smaller than the former. quantity. A change of supply
represented by S2S2, indicates that at the same price of OP, a larger quantity OQ2 is supplied.
Factors affecting change in supply
These factors cause a change in supply:
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high consumption of their own product by the producer (less product is supplied to the
market)
change in cost of production
change in technique of production
changes in the weather
taxation of commodities
future expectations.
Pricing
The pricing of commodities in a perfect market occurs through the interaction of the market
forces of supply and demand. The price of the product is determined by the demand in relation to
the conditions of the supply at a particular time. At some point, these two forces are brought into
balance (or equilibrium). The equilibrium price is the price at which demand, and supply are
equal.
Figure 4.13 shows that at the price OP, the quantity supplied (OQ) is the same as the quantity
demanded (OQ). The point at which the demand curve DD intersects with the supply curve SS is
called the equilibrium point. At any price higher than the equilibrium price OP, supply will
exceed demand and the sellers will have a substantial quantity of unsold products. At any price
lower than the equilibrium price OP demand will exceed supply and there will be a shortage of
that particular product.
The effect of changes in demand and supply
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An increase in demand tends to increase price and increase supply.
A decrease in demand has the opposite effect, resulting in a lowering of price and the
quantity supplied.
An increase in supply tends to lower price and increase demand.
A decrease in supply will increase price and reduce the quantity demanded.
Elasticity of demand and supply
Elasticity measures the degree of responsiveness of each of the market forces (supply and
demand) to changes in price. It also enables the government to set up appropriate policies to
regulate the economy. The elasticity of demand (Ed) is the degree of responsiveness of the
demand for a product to a change in its price. It is expressed as:
Elasticity of demand may be:
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elastic — greater than 1: a small change in price results in a big change in the quantity
demanded
inelastic — less than 1: a considerable change in price causes a small change in the
quantity demanded
unitary — equal to 1: a change in the price brings about a proportionate change in the
quantity demanded.
Similarly, elasticity of supply (Es) is the degree of responsiveness of supply to a change of price.
Elasticity of supply may be:
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elastic — greater than 1: a small change in price results in a big change in the quantity
supplied
inelastic — less than 1: a considerable change in price causes a small change in the
quantity supplied
unitary — equal to 1: a change in the price brings about a proportionate change in the
quantity supplied.
Price mechanisms
A price mechanism refers to a wide variety of ways to match up buyers and sellers. It enables the
distribution of scarce goods to consumers and scarce factors of production to producers. The
demand of consumers, or consumption, encourages producers to expand their business. This
stimulates demand for factors of production and for an increased supply of commodities.
Demand, supply, and price are dependent on one another, and the equilibrium price equates de
with supply.
The government may put price controls on certain commodities. Max prices may be fixed for
certain products to protect consumers, especially members of the community. Minimum fixed
prices may be set to F agricultural producers against a fall in income due to a bumper harvest.
The purpose of raising prices by taxation is to reduce consumption of comm (which are thought
to be harmful to the economy. This can be done to the loss of foreign exchange as a result of the
import of goods. Subsidies are imposed on certain foodstuffs to keep the cost of living down or
to encourage domestic production.
Trade Agreements
14. Evaluate the effects of international trade agreements on the agricultural sector and
peoples of the Caribbean
Specific international trade agreements:
(a) Caribbean Single Market and Economy (CSME)
In 2006, after considering the challenges of an increasingly globalised economy and the need to
increase competitiveness of its goods and services, the Caribbean Community (CARICOM) set
up the Caribbean Single Market and Economy (CSME).
The CSME (Figure 5.1) enables free movement of goods, services, capital and people across
member states in the Caribbean. This means that production and marketing operations are
promoted and supported in an enlarged, single economic area. There is a better environment for
the competitive production of goods and services for external and intra-regional markets.
Entrepreneurs in the CARICOM region are able to:
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use their talents and resources more fully
trade freely without hindrance
establish and service markets in other states
attract capital or invest and use funds in another state
hire skilled workers from any of the member states, resulting in greater efficiency,
competitive production, and increased profits.
At present, there are 15 full members of CARICOM of whom 12 are members of the CSME.
Montserrat is a full member of CARICOM and awaits approval for membership of the CSME.
Haiti and the Bahamas are full members of CARICOM but have not joined the CSME. The
introduction of a single currency is scheduled for completion between 2010 and 2015. The
removal of trade barriers and the opening up of new opportunities for over 6 million CARICOM
nationals (14 million if Haiti is included) enables the CSME to stimulate growth.
Free movement of goods
To enable free movement, the following measures will be taken:
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there will be no import duties on goods originating from the CARICOM region
tariffs and quantitative restrictions will be removed in all member states
intra-regional imports will be treated differently from extra-regional imports
there will be agreed regional standards for the production of goods within the CARICOM
region providing a major incentive for high quality products from producers and
manufacturers
CARICOM producers and manufacturers will be able to market their goods to over 6
million people (14 million if Haiti is included).
Free movement of services
Member states will be required to:
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remove impediments restricting the right of any CARICOM national to provide regional
services
ensure that nationals from other member states have access to land, buildings and other
factors of production on a non-discriminatory basis for the purpose of providing services
to the region.
Free movement of capital
Free movement of capital will:
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enable CARICOM nationals to transfer money to any member state electronically and
also through bank notes and cheques; no new monetary restrictions will be added, and
existing ones will be removed
promote and increase investment regionally
allow firms access to a wider market for raising capital at competitive rates, so enabling
the productive sectors to become more competitive regionally and internationally
foster the development of a regional capital market which will increase the attractiveness
of the region for investment.
Free movement of people
Free movement of people will:
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promote a closer union among the people of the CARICOM member states
abolish discrimination on grounds of nationality in all member states
entail the removal of work permits for certain categories of workers
encourage an interchange of managerial, professional and technical expertise within the
region
enable certain categories of workers to travel freely to member states and enjoy the same
benefits and rights regarding conditions of employment as those given to national
workers.
The CSME is of particular importance in the agricultural sector, making it easier for the
marketing of produce, securing investments and the movement of workers. All the points made
generally about the free movement of goods, services, capital and people can be applied to any
agricultural enterprise or associated business.
(b) World Trade Organisation (WTO)
WTO is an international organisation which promotes free trade by persuading countries to
abolish tariffs on imports and other barriers to trade. It is the only international body that
oversees the rules of international trade.
Functions of the WTO include:
• checking free trade agreements
• settling trade disputes between governments
• organising trade negotiations.
Decisions made by the WTO are absolute and all member countries must abide by its rules. Any
country that breaches the rules may have trade sanctions imposed on it. As of July 2008, there
were 153 member countries, representing 95% of world trade.
Since 2001, the WTO has been trying to negotiate a trade agreement which would benefit poorer
countries; but it has been hampered by disagreement between exporters of agricultural
commodities in bulk and countries with large numbers of subsistence farmers. These countries
want to ensure that there are safeguards to protect farmers from a drop in prices or a surge in
imports. In 2008, member countries met in Geneva to resolve the problem, but the talks failed.
Some critics maintain that free trade only leads to the rich countries becoming richer and the
poorer ones poorer.
Free trade between Caribbean countries is now established, but better access to world markets
could benefit the economy of the region. The WTO is working to encourage trade agreements
that promote the economies of poorer countries.
(c) Free Trade Area of the Americas (FTAA)
At the Summit of the Americas in Miami in December 1994, 34 countries of the region agreed to
the establishment of a Free Trade Area of the Americas (FTAA), in which barriers to trade and
investment were to be progressively eliminated. The ultimate goal was to create an area of free
trade and regional integration. The main objectives are shown in Figure 5.2.
These objectives are similar to the objectives of CARICOM and the WTO, with the emphasis on
removing trade barriers and opening up markets to member countries. Attempts have been made
to ensure that any negotiations are transparent, considering the differences in the levels of
development and the size of the economies in participating countries. It was agreed that
negotiations should contribute to the raising of living standards, the improvement of working
conditions and protection of the environment.
FTAA agreements are consistent with WTO rules. Member countries may negotiate and accept
obligations individually or collectively as a sub-regional group for example, CARICOM. Some
trade expansion has occurred through bi-lateral trade deals with member countries and by the
enlargement of existing agreements.
The FTAA has not yet come into full effect: its target deadline was 2005 but this was missed. In
June 2009, a fifth Summit of the Americas was held in Trinidad and Tobago. The focus was on
human prosperity, energy security, climate change and sustainable development.
The FTAA has not progressed as far as CARICOM and the CSME, so its benefits to Caribbean
countries are limited. Where separate bi-lateral agreements have been reached, there are
advantages to participating countries, but these agreements are not widespread and do not
involve all countries.
(d) The Lome Convention (Lome I -IV)
The Lome Convention was a trade and aid agreement between the European Community (EU)
and 71 African, Caribbean and Pacific (ACP) countries. The first agreement was signed in 1975.
It came into force in 1976 and provided a framework for co-operation between the members of
the European Community and the developing ACP countries, which were formerly British,
Belgian, Dutch and French colonies. The Convention allowed ACP agricultural and mineral
exports to enter the European Community free of duty, a quota system for sugar and beef and 3
billion Euros of financial aid. Since 1976, the agreement has been renewed three times (Lome II,
III and IV) and in 2000 it was replaced by the Cotonou Agreement. This was signed by 15
members of the EU and 79 ACP countries.
The partnership between Europe and the ACP countries has charted a course from decolonisation
to globalisation, geared towards global and political issues. The Cotonou Agreement is expected
to run for 20 years. It focuses on a global approach to development and involves the progressive
abolition of obstacles to trade between the countries in accordance with the rules of the WTO.
The Cotonou Agreement aims to get rid of poverty in ACP countries and to promote their entry
into the world economy.
To stop the poverty, ACP countries need to:
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face up to the challenge of competition on the international market
increase production, supply and the competitive nature of their products
maintain high standards of quality and performance
attract inward investment.
To improve the efficiency of production in the ACP countries, the Cotonou Agreement makes
provision for granting subsidies for long-term development support and an investment facility to
promote the private sector. The allocation of financial resources will be based not only on their
needs but also on their performance levels.
The challenges facing the ACP countries are large but not insurmountable. Enormous effort is
required to strengthen their capabilities, relying not only on their own resources but also on
external assistance as provided by the Cotonou Agreement. In this way, they will be able to adapt
to developments in today's world.
(e) International Sugar Agreement (ISA)
In 1992, the International Sugar Agreement (ISA) was negotiated.
The objectives of the ISA are to:
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ensure international co-operation in connection with world sugar matters
provide a forum for intergovernmental consultations on sugar and on ways to improve the
world sugar economy
make trade easier by collecting and providing information on the world sugar market and
other sweeteners
increase the demand for sugar, particularly for non-traditional uses.
Farm Financing and Support Services
15. Evaluate the process of obtaining capital from established sources
How to Obtain Loans
To obtain a loan from a reputable financial institution, farmers need to fulfil certain requirements
(see Figure 6.2).
Farmer’s Registration
The applicant (farmer applying for a loan) must be a registered farmer. In Trinidad and Tobago,
the registration of farmers is done by the Ministry of Agriculture at regional and county
agricultural offices. Farmers who are registered are more favourably considered for loans,
subsidies and other national incentives. In other territories, such as Jamaica, registration is via
the Ministry of Agriculture.
Creditworthiness
The creditworthiness of a farmer is a measure of the farmer's ability to pay off debts. It is
determined on the basis of assets, liabilities and net worth. From information supplied by the
applicant, the lending institution will know the monthly income and expenses of the farmer. They
then judge whether he will be able to repay the loan if it is granted.
Risk and uncertainty apply to agriculture so limited loans are sometimes made to farmers on the
basis of their creditworthiness. Often such loans are insufficient for the farmer to set up a new
enterprise which could generate substantial profit.
It is an advantage for a farmer to have a good credit-rating and reputation. A farmer who has
borrowed money previously and repaid the loans promptly is more favourably treated than
someone who has not asked for credit before. Normally, credit-rating and reputation are
researched by the lending agency as part of the application process.
The farm proposal and budget estimate
The farm proposal outlines the farmer's intentions. It is a document which details his objectives,
the enterprises he proposes, his farming techniques, the resources needed and the anticipated
output and income. Using his farm proposal, the farmer prepares and submits a budget estimate
for each of the enterprises he intends to pursue. The budget estimate justifies the amount of loan
required for the proposed farming business. Some farmers approach financial agencies without
detailed proposals and budget estimates. Renowned lending institutions require carefully
prepared proposals and budget estimates and will not offer loans without these.
Farm records and experience
Farm records provide documentary evidence of previous enterprises and justify the experience of
the applicant. Many farmers keep poor farm records and are unable to satisfy the lending
institutions as to their ability to run an enterprise successfully. It is difficult to judge the farming
experience and 'track record' of an applicant if there are no records.
Collateral, security, guarantor
Financial institutions make sure that the farmer has some form of collateral or security to offer
that will cover the total amount of the loan. This may be in the form of property such as land, a
house, farm machinery, equipment, or livestock. Often, a relative or friend serves as a guarantor,
pledging their property as security for recovery of the loan should the farmer fail to repay it.
Some farmers who operate small farms lack the collateral for loans and cannot find guarantors
willing to pledge their personal property as security.
Lifestyle and character
Honesty, sincerity, perseverance, and a determination to work hard are character traits which are
highly regarded. Farmers should aim to be good role models as they transact business with
financial institutions.
Problems with obtaining loans
Lack of collateral, poor creditworthiness, insufficiently detailed farm proposals and budget
estimates have been mentioned already as problems. In addition, farmers who find it difficult to
meet the loan requirements of some institutions may be forced to take out loans with high rates
of interest, or to make repayments over a shortened period of time. These types of loans are
stressful for farmers, particularly if the agricultural enterprise is still being developed and not
producing much income.
Credit supervision
Some farmers may use their loans for purposes other than agriculture. Any farmer who obtains a
loan from the Agricultural Development Bank undergoes credit supervision, where trained staff
make regular farm visits, give technical advice and pay the fanner the money in phases until the
enterprise is completed.
16. Discuss the concept of cooperatives
A co-operative is a legal organisation which enables its members, as a group, to improve their
economic status in a competitive society. A co-operative is a business venture. It is voluntarily
and collectively owned, controlled, operated, patronised and managed by its members on a nonprofit or cost basis for the economic benefit of all its members. A co-operative (see Table 6.1)
can be distinguished from any other business organisation by its guiding principles. These
principles are referred to as the 'cooperative concept' (see Figure 6.3).
Roles and functions of co-operatives
Co-operatives fulfil the following roles:
•
•
•
•
•
•
•
•
•
•
promote voluntary, open membership
pursue business ventures
encourage active participation and teamwork
generate collective ownership
encourage equity in sharing
operate on a non-profit or cost basis
improve the economic well-being of members
provide desirable services to satisfy patron-owners
generate greater bargaining power for better prices and contracts
attract governmental aid, resulting in benefits for patron-farmers.
Co-operatives are important organisations in many countries and fulfil many functions. A cooperative helps its members to reduce operating costs, enables them to increase their levels of
production so that they can increase their income, and challenges them to produce better quality
produce and become more competitive. In a wider sense, co-operatives encourage agricultural
development and reduce poverty.
Group demonstrations and technical training sessions are organised more easily through cooperatives as members share a common interest. Greater interest in productivity and business
enterprise is created.
Types of co-operatives
Co-operatives can be grouped in two ways: by their function or by their links with other groups.
Co-operatives grouped by function
There are seven types of co-operatives (see Table 6.2) which perform different functions.
Co-operatives grouped by links
Most co-operatives are linked in groups at local, regional and national levels:
•
•
•
Local co-operatives offer members representation and services at the village or district
level.
Regional co-operatives provide services and representation at the county or regional
level, based on nominees from local co-operatives.
National co-operatives supply representation and services at national level, through
nominees from the regional co-operatives, who are representatives of the various local
groups.
There are also:
•
•
independent co-operatives, not affiliated to any other co-operatives
federated co-operatives, comprised of small local co-operatives, operating as an
integrated unit and banded together for greater economic power and efficiency
•
centralised co-operatives, composed of delegates from local co-operatives, operating as a
centralised control unit and initiating directives from the local co-operatives for action;
the structure of these means that each member cannot participate directly in the decisionmaking process.
Managing a farmers' co-operative
Management of a farmers' co-operative is a shared responsibility between the Chief Executive
Officer, the Board of Directors and the patron-owner-members. Policies and regulations drawn
up by the Board and approved by the general membership are used for the day-to-day running
and management.
Management is aimed towards the economic well-being of the farmers, who are the patrons,
users and owners of their co-operative. It uses managerial talents and approved policies to
achieve results using the limited resources available. Problems may sometimes arise for the
management team (see Figure 6.4).
Limited Capital
Co-operatives operate with limited amounts of finance (or capital) which come from its patronmembers. It is not possible to provide a wide range of services or to generate funds through
public investment, as in a non-co-operative business. Such procedures are not allowed according
to the co-operative concept. This means that the co-operative may have to seek credit or ask
patron-members for more money to finance the necessary services. It is important that the farmer
elected as the manager or Chief Executive Officer has the skills and experience to make
decisions promptly.
Business volume
The volume of business transactions fluctuates between high and low. It depends on how often
members use the services they have provided for themselves. High levels of business volume
help a co-operative. It is up to members to ensure that they use the services to sustain their cooperative.
Membership issues
In a co-operative, each member is a patron, a user and an owner. Every member needs to
demonstrate a sense of ownership, loyalty and commitment. In some cases, members do not give
their full support by way of their share contributions and business patronage. Members need to
face up to the shared responsibility of supporting their co-operative investment.
Local Competition
Co-operatives often face competition from the local business community who feel that they are
an economic threat to their clients and business. Large local businesses use bulk buying and
obtain discounts from merchant suppliers. In retailing their goods, they may offer lower prices
than the co-operatives. Members of cooperatives need to focus their efforts on good
management, greater production and better quality.
Global issues
Issues such as globalisation, trade liberalisation, competitiveness and quality standards directly
affect farmers' co-operatives. Such issues may make it difficult for co-operative managers to
meet the challenging task of international requirements and to educate, train and motivate their
members.
17. Evaluate the incentives that may be given to farming
Risk and uncertainty
The agricultural sector is affected by factors which involve risk and uncertainty.
These include:
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•
•
the weather
natural disasters (volcanoes)
over-production and under-production
• fluctuating market prices
• increasing costs of inputs
• unstable incomes of farmers.
Governments can help to stabilise production, market prices and farm incomes through subsidies
and price support policies.
Price support
Farmers can be guaranteed minimum cost-based prices by the government, referred to as
guaranteed prices, for selected crops or commodities. The commodities may be export-oriented
(sugar cane, cocoa, coffee, citrus fruits and bananas) or for domestic consumption (rice, root
crops, milk, mutton and eggs). These guaranteed prices are incentives to production. They
demonstrate commitment on the part of the government. In Trinidad and Tobago, price support is
offered to farmers for the commodities shown in Table 6.3.
Subsidy
A subsidy is a financial incentive to farmers or producers for infrastructural development,
technical operations, purchasing farm inputs and establishing agricultural enterprises. Normally,
specific subsidies are offered to farmers, but the government's commitment is only towards a
percentage of the cost and up to a maximum amount of money. Some examples are listed in
Table 6.4, overleaf.
In many Caribbean countries, there are tax exemptions for agricultural inputs and import duty
concessions on farm machinery. Most domestic unprocessed foods are exempt from general
consumption tax. These measures encourage agricultural enterprises and create employment in
the agricultural sector.
The purpose of price supports and subsidies
The main function of price supports and subsidies are to:
•
•
•
•
•
speed up the growth of agricultural output
stabilise agricultural production, market prices and farm incomes
increase the local market supply of commodities for home consumption and export
speed up or encourage growth in the output of specific commodities
provide a more regular income for farmers and producers.
In addition, these incentives enable the government to achieve its targets in agriculture and to
speed up innovation in farming.
Farm Organization and Planning
18. Prepare different types of farm records
Farm management is essential to agriculture because agricultural enterprises by themselves do
not guarantee profitability. Farm resources need to be organised and managed and the starting
point of this is farm planning. The plans outline the intentions of the farmer regarding the use of
resources, the enterprise to be pursued and the anticipated production. There are four questions to
be answered before starting on any new agricultural enterprise. These are:
•
•
•
•
What to produce?
Why chooses the product?
How much to produce?
How to achieve the production?
The choice of product is determined by factors such as the location of the farm, the experience of
the farmer, the demand and market price of the commodity, and the resources available. A
detailed farm plan, taking into consideration the answers to the key questions, eliminates some
uncertainty. It also enables the farmer to apply for a loan from a reputable financial institution. If
progress of the planned enterprise is recorded on a regular basis, there is information available
for future use.
Farm planning may be carried out on a short-term or a long-term basis.
Short-term planning relates to planning for enterprises for 1 year or for those with a short
production cycle. The main objective is to make as much profit as possible, so the farmer
chooses crops and livestock which will provide income in a few weeks or months on a
continuing basis. Such enterprises could be vegetable production (Pak choi, tomatoes and beans)
or poultry production (broilers, ducks).
Long-term planning refers to planning for periods of longer than 1 year. Usually, plans are made
for enterprises that need some time (1-3 years) to become established before production begins.
Examples are tree crops (citrus, mango, avocado) and dairy farming (heifers and cows for milk
production).
The objective of long-term planning is to develop and expand resources on the farm so that the
earning capacity and asset value of the farm will increase in the future. If a farmer is considering
an enterprise requiring a long-term plan, then it is advisable to undertake one or two short-term
enterprises to produce some income until the long-term projects become productive.
Poultry farming - a short-term enterprise. Growing citrus trees — a long-term enterprise.
Farm records
Farm records detail essential data about agricultural enterprises, and the farm as a whole, in
written or electronic form. The data should include records of transactions, facts, information and
observations. While a farmer may remember some of the transactions carried out on a day-to-day
basis, it is not possible to remember details of figures, quantities and dates so it is vital to keep
written records. The different types of farm records are summarised in Table 7.1.
Farm records should/The characteristics of good farm records.:
•
•
•
•
•
•
be easy to do and keep
serve a definite purpose
be simple, useful and effective
be accurate and complete, giving the essential information
be kept consistently
be easily accessible.
Farm inventory
A farm inventory is a record of the farm resources, in terms of quantity and value, at the
beginning and end of an accounting period (normally one calendar year). It includes land,
machinery, tools and equipment, buildings, livestock, field crops and materials. Inventory
records may be done collectively or separately for each of the resources, such as land, machinery
and buildings. Farmers with large farms prefer separate inventories for each resource because it
is easier to show continuity on a yearly basis. The information on each resource can be found
more readily and necessary action can be taken more promptly. An example of a separate
inventory system for tools and equipment is shown in Figure 7.4.
Production records
Production records are used for crop and livestock enterprises to follow the prof and determine
the performance and productivity of different crop varieties breeds of animals. With such
records, farmers can find out whether inputs, as feed and fertiliser, are being used efficiently.
This will ensure that high yield and profitability are obtained on a consistent basis. For example,
livestock records can be kept to show the milk production of individual cows or the feed
conversion ratio (FCR) when a particular type of feed is used for fattening weaners. Similarly,
there are record forms for egg production and other types of livestock enterprises, such as rabbit
and broiler production.
Records for rabbit production
As an example, records for rabbit production should include:
•
•
•
•
•
an animal inventory to include total number of bucks, does and weavers
breeding records for each buck and doe with breeding dates, including number in each
litter of each doe, number of live births and mortality, and remarks (e.g., whether the doe
was a good mother)
feeding records, to include feed given, feeding regime, growth rate and feed conversion
ratios
medication records
weight at marketing or slaughter, cost of production and income from sale.
From the records, a farmer can work out whether the enterprise makes a profit or a loss. They
also highlight problems where savings or improvements can be made to make the enterprise
more profitable in the long term. In assessing the enterprise, the farmer also needs to take into
account the cost of the buildings and the labour.
Records for crops
Crop production record forms show the performance of the crop variety, the yield and how much
profit (or loss) was made. An example of a record form for a crop of lettuce is shown in Figure
7.5.
Chemical treatment record
Any treatment given to crops or livestock is a consumable resource and needs to be offset against
any profit made. Chemical treatments include fertilisers and pesticides for crops and medication
and concentrates and drugs for livestock. Figure 7.6 shows a record form for the use of fertiliser.
In the 'Remarks' column, the farmer should record the crop to which fertiliser is applied. This is
cross-referenced on the crop production record and the cost is offset against the profit from sale
of the crop.
19. Distinguish among gross farm income and net farm income, gross margin and net profit
In small agricultural enterprises, financial records may take the form of income (farm receipts)
and expenditure (farm expenses). Using these, a farmer will determine his profit or loss.
In larger businesses, the financial records include:
•
•
•
•
the profit and loss account (referred to as the cash account)
the assets of the farm
the liabilities of the farm
the net worth statements or balance sheet.
Profit and loss account
Figure 7.7 shows a profit and loss account for one month. The income is on the left-hand side
and gives details of produce sold and price achieved. The expenditure is on the right-hand side
and includes labour, fuel and other consumables. The only details missing from this account are
the quantities of produce sold and the consumables used. These would appear on the records for
each enterprise on the farm.
The balance sheet, or net worth statement, shows the value of assets left for the farmer after all
claims and liabilities against the business have been paid.
A balance sheet is shown in Figure 7.8. The assets include the land, buildings, machinery and
equipment, field crops, livestock and cash. The liabilities include unpaid rent and wages,
mortgage commitment and money owing to creditors.
Income
Income is money earned by producing commodities which are in demand and selling them at
current market prices to wholesalers, retailers and consumers. After subtracting the costs of
production, the farmer uses the income to purchase necessities for the family, educate children,
invest in savings, and buy the inputs required to continue the farm operations.
In determining income, several factors have to be considered:
•
•
•
fixed inputs and fixed costs (total fixed cost)
variable inputs and variable costs (total variable cost)
output and the market price gained (total income).
Production records
Figure 7.9 shows a production record for a duck rearing enterprise, where all the costs are set out
and the total income shown.
From Figure 7.9, you can see that the total income is the market price multiplied by the number
of ducks sold. This is $90 000 and represents the gross income, that is the income regardless of
the cost of the inputs.
gross income =total income
The net income is the gross income minus the total cost of the inputs (the total fixed cost plus the
total variable costs). In this case, the net income is $52 000 because the total cost of the inputs is
$35 500 + $2500 (this equals $38 000). So, $90 000 - $38 000 = $52 000.
Having seen how net income is worked out for one agricultural enterprise, it is easy to see how
gross farm income and net farm income can be calculated. The farmer needs to add up the gross
income from all the enterprises, add up the total cost of the fixed and variable inputs, and use
these figures to calculate a net farm income.
Two other terms often used in connection with balance sheets are gross margin and net profit.
Gross margin is equal to gross income minus variable costs. It is the difference between the sales
and the production costs.
Gross margin is an indication of how profitable an enterprise is. Those agricultural businesses
with higher gross margins will have more money left over to spend on other operations. Net
profit is a measure of profit over time, and it is calculated by subtracting all the costs of a
business from the receipts. This means subtracting all the costs from the gross profit. Net profit
can be shown on the profit and loss account for a business.
20. Develop a partial and a complete budget
A complete budget is also known as a total budget or a whole farm budget. It is prepared for a
farm which has a new owner or new management. It can also be used when there is a major
change in the resources and enterprises of a farm, or when a complete re-organisation is
undertaken. It is usually prepared when an existing farm wants to change its systems of
production and introduce improved technology (see Figure 7.10).
A partial budget is prepared when there is change in a specific aspect of the existing farm plan
that requires some modification to the budget. For example, a farmer may decide to rear 6000
broiler birds instead of 4000, or purchase a pick-up truck
instead of hiring transportation. In such situations, most of the income (receipts) and expenses
(costs) in the existing budget will remain the same and only some will change. A partial budget
identifies the income and expenses that will change and sets out how additional costs and income
will affect the change in profit.
The financial gains and losses are set out in the partial budget as:
•
•
debits: additional costs and reduced income
credits: additional income and reduced costs.
21. Explain the relationship between budgeting and decision making
Decision Making
Decision-making is the ability to make sound objective judgements and initiate follow-up action,
based on all data and information available. It is also the process of identifying, analysing and
selecting the right course of action to solve a problem.
All farmers and entrepreneurs involved in farming are required to make decisions about farm
plans, budgets, work schedules, modifications and improvements. Sound decision-making results
in farm profitability and development of the business.
Decision-making (see Figure 7.12) is not a simple matter for farmers. They have to consider
limited resources, changing weather, the unpredictable nature of production, the ups and downs
of the market and natural disasters. Hasty decision-making can bring economic losses and
bankruptcy.
Budgeting
Budgeting is estimating the quantity of inputs, costs, outputs, income and profit related to an
agricultural enterprise. It focuses on the physical components (what to produce, how to produce
it and how much to produce) and the financial components (anticipated costs, returns and profit).
Budgeting is an essential process in farm planning.
Reasons for budgeting
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•
•
•
•
It helps the farmer to decide which farm plan or agricultural enterprise to choose.
It allows the farmer to compare the profitability of different enterprises.
It makes the preparation of whole farm budgets easier.
It provides documentary evidence for financial institutions when a loan application is
made.
It makes it easier for the farmer to control the finances of the farm.
Section B: Crop Production
Soil and Soil Fertility
22. Describe the process of soil formation
Soil on the Earth is like the skin on a mango, except that soil varies in composition, type, and
thickness at different places. Soil is formed by the weathering of rocks. Weathering is the
decomposition of Earth's rocks through direct contact with the planet's atmosphere. Soil may be
found overlying these rocks or it may be transported by natural forces, such as water, wind, and
glacial action, and deposited at other sites. Soil is a mixture of mineral particles, organic
material, air, and water. It provides an environment for the growth of plants as well as a habitat
for vast numbers of soil organisms. Weathering involves the breakdown of bedrock (unweathered
rock) into smaller and smaller particles, together with the activities of plants, animals and
humans. The type of soil formed depends on the parent material, or bedrock. Where the parent
material is shale, then a clay soil is produced. Where the parent material is sandstone then sandy
soils result. Soils formed in sloping or mountainous areas are shallow due to erosion, usually by
water. If there is a good vegetative cover with organic matter as a top layer, then soil will form
even on hillsides. But if there is erosion, then soil development occurs only in the foothills and
valleys with very little soil formed in higher regions. There are three forms of weathering:
mechanical (or physical), chemical and biological.
Mechanical (or physical) weathering
Weathering due to ice Physical weathering is the breakdown of rocks by mechanical means. If
forces arc applied to rock, either within the rock or from an external source, then the rock breaks
down. The most important type of physical weathering is brought about by frost. In areas where
the temperature falls below 0 °C, any water that has filtered down into the cracks in the rock will
freeze. As water freezes it expands and takes up a larger space, exerting pressure and causing the
cracks to get bigger. When the temperature rises, the ice melts, and the larger crack can hold
more water. When the temperature drops again, there will be more ice formed, yet more pressure
and the crack will get deeper. Eventually this process will break up rock into smaller fragments.
Weathering due to moving water
Water in streams dislodges and carries away rock fragments. These collide, disintegrate, and get
worn down into small, rounded pebbles and eventually miner particles. Heavy rain also dislodges
rock fragments and washes them into rivers. In coastal areas, waves beat on rocks causing them
to disintegrate.
Weathering due to wind
In very dry regions, wind containing sand particles has an abrasive action at wears away the
surfaces of rocks. The particles of rock can be carried to other sites where they are deposited
Glaciers
Glaciers can cause weathering as they move down mountain slopes. They erode rocks,
transporting and depositing materials many kilometres away on lower ground.
Weathering due to the sun
In the daytime, the sun heats up the surface of rocks causing them to expand. At night, when
temperatures drop, rock cools and contracts. Over a long period, the continued expansion and
contraction of the rock will cause it to fragment. This is due to stresses set up as the surface
expands more than the centre of the rock, causing the surface layers to break away.
Chemical Weathering
Chemical weathering is weathering which alters the chemical nature of the rock. The main
factors which cause chemical weathering are water, oxygen and carbon dioxide.
Water
Rocks are made of materials which have different levels of solubility. For example, sodium
chloride (common salt) is soluble and is only found as a solid (rock salt) in very dry areas. Other
rocks which are soluble, but less so, include gypsum (calcium sulphate) and carbonates, e.g.,
calcium carbonate. Silica, a component of sand, is only slightly soluble in water.
Water can change the minerals in rocks. If water is added to some soil minerals it causes
chemical changes and new minerals are formed. For example, potassium may be removed from
the rock known as feldspar, leaving aluminium and silicon. These can then re-crystallise forming
clay.
Oxygen and carbon dioxide
Oxidation occurs when minerals in rock combine with atmospheric oxygen, or the oxygen
dissolved in rainwater. The minerals are converted to oxides which are more likely to break
down or undergo weathering. For example, when water combines with the iron-containing rock,
olivine, ferrous oxide is released. The ferrous oxide becomes oxidised by oxygen in the
atmosphere to ferric oxide, known as haematite.
When carbon dioxide in air dissolves in rainwater, carbonic acid is formed. This is a weak
inorganic acid. As rainwater filters through rock containing carbonate, such as limestone, the
minerals in the rock dissolve and the rock breaks up. In most humid regions, other dilute
inorganic acids (such as nitric and sulphuric), and some organic acids are also important in
weathering rocks.
Biological Weathering
Biological weathering refers to disintegration of rocks and the formation of soil through the
activities of living organisms. If there are cracks in a rock, some soil will gather. If a seed
germinates in this soil, its growing roots exert pressure and eventually the rock splits. Animals
which tunnel into the soil, such as worms, ants and moles, contribute to weathering by bringing
new material to the surface where it is exposed to rainwater and the atmosphere.
Plants rot and are decomposed by micro-organisms in the soil. In this process organic acids,
called humic acids, are released into the soil and break down rock minerals. The plant roots also
release carbon dioxide into the soil and carbon dioxide breaks down carbonates (see above).
Volcanic activity and soil formation
Volcanic activity has occurred in several Caribbean islands, giving rise to igneous rocks and
volcanic soils. Volcanic soils are found on Grenada, St Vincent, St Lucia, Dominica and
Montserrat. The soil on slopes and in the valleys of the volcanic cones is derived from the lava
thrown out when an eruption occurs. Volcanic soils are dark grey and have a granular structure.
They are porous and high in sulphur, phosphorus and potassium. At the time of an eruption,
volcanic ash is dispersed by volcanic pressure and by the wind. It settles on the soil, where it
appears as a fluffy, greyish layer. In the years following an eruption, it becomes incorporated into
the topsoil by weathering and cultivation by farmers. It is not easy to see decomposed organic
matter in such soils because of their colour.
Organic matter
Organic matter consists of the dead and decaying remains of plants and animals. The
accumulation of organic matter on the soil surface protects it from erosion and encourages soil
formation. Organic matter provides a source of energy for micro-organisms which help to form
humus. Humus is a brown or black substance formed from decayed, and partially decayed, plant
and animal material.
•
•
•
Humus is important as it:
helps to bind sand and clay particles into clumps producing a granular soil (it improves
the texture)
contains some of the nutrients which plants need.
Effects of soil organisms on soil
Soil micro-organisms, such as bacteria and fungi, break down organic matter to humus.
Earthworms (see Figure 8.2) contribute to soil formation and soil fertility because they:
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•
•
•
make tunnels allowing air down into the soil
create tunnels which contribute to the drainage of the soil
make their tunnels by swallowing soil, so that the organic matter is digested, and mineral
particles pass out of the gut back into the soil. In some species, egested soil is deposited
on the surface as a 'worm cast' and consists of finely ground particles. The effect is to mix
up layers of soil.
pull leaves into their tunnels for food, increasing the organic content of the soil and
contributing to mixing.
Other burrowing organisms, such as insects, insect larvae, slugs, spiders and woodlice, keep soil
loose and aerated. Their faeces contribute to the organic matter and provide food for microorganisms. Plant roots bind soil particles together and also create channels for the cycling of
nutrients within the soil.
Effect of human activities on soil
Several human activities affect the formation and fertility of soil:
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•
•
•
land clearing interrupts the accumulation of organic matter
grading and levelling of land removes the topsoil and often sub-surface layers as well
mining, quarrying and soil removal upset the activity of soil-organisms and soil
formation
ploughing disturbs soil profiles but it does break up rock fragments.
23. Describe a soil profile with reference to major soil horizons
A soil profile is a vertical section dug down through the soil showing a natural sequence of
horizontal layers of soil. It can be revealed by digging a rectangular pit so that one wall of the pit
exposes the colours and textures of the different layers. Alternatively, a soil auger can be used to
remove a core of soil and the different layers can be identified. Figure 8.3 shows a soil auger in
use.
Soil horizons
Each layer, or soil horizon, has different physical and chemical properties. The development of a
soil profile is affected by the topography of the land, soil texture, drainage and soil erosion. In a
typical, undisturbed, well-drained forest soil, at least four major horizons can be recognised.
Horizons are named 0, A and B and may contain one or more sub-horizons, which are named O1,
O2, A1, A2, A3 and B1, B2, B3.
The importance of soil profiles
For the farmer, the soil profile is relevant in terms of land preparation needed before planting
crops. During ploughing, the furrow slice or topsoil is cut and inverted by the ploughshare.
Depending on the thickness of horizons 0, A and B, this slice may include horizon 0 and part of
horizon A, or horizon 0, horizon A and part of horizon B.
The area beneath the furrow slice is referred to as the subsoil. If there is a hardpan or impervious
layer, resulting from the accumulation and compaction of leached deposits, then the subsoil may
need to be broken with a sub-soiler.
Depending on the soil profile, the farmer can decide on the depth of ploughing, selection of
equipment for tillage, and the choice of crops (shallow-rooted or deep-rooted).
Types of Soils
Latosols
Most soils in the Caribbean are latosols, formed when
rainfall is greater than evaporation and there is rapid
leaching of dissolved minerals. These soils support
dense, tropical rainforest. The organic layer (0
horizon) of leaves and litter is usually less than 25
mm deep. Because of high temperatures and
humidity, organic matter decomposes very quickly.
The A horizon is 300 mm deep and a dark brown to
reddish colour. The clay content makes the soil sticky.
Rendzina
Another type of soil in the Caribbean region is a
rendzina, which develops over limestone rocks. This
soil is thin, with the A horizon 200 to 250 mm deep.
The soil is dark in colour due to the amount of humus
and there is much animal activity. Although there are
rendzinas in many Caribbean countries, they are not
widespread. The best examples are on the plateaux of
Jamaica.
24. Describe the major components of soil
Soil is made up of:
•
•
inorganic matter (mineral particles)
organic matter
•
•
water
air.
The mineral particles and the organic matter (about 50%) are referred to as solids. The water and
air, which make up the remaining 50%, are referred to as pore space. By volume, the solid
fraction is made up of 45% mineral particles and 5% organic matter. The pore space fraction is
divided into 25% water and 25% air, both of which vary according to weather conditions.
Inorganic matter
The mineral component of soil, derived from the weathering of rocks, is porous and consists of
stones, gravel, sand, silt and clay. These components vary in size and composition as shown in
Table 8.2.
The coarser mineral fragments may be bound into lumps, clods or aggregates by humus and
colloidal clay particles. These aggregates are porous and contain pore spaces for soil air and soil
water.
Organic matter
Organic matter consists of fresh or decaying plant and animal residues and humus. Humus is the
end product of the decomposition of organic matter by micro-organisms. It is black or dark
brown. In the tropics and sub-tropics, organic matter is broken down rapidly to humus by soil
micro-organisms. Although the organic content of soils is small (3 % to 5%), it benefits the soil
and improves crop growth and production in the following ways:
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it loosens clay particles, serving as a 'granulator'
it binds mineral particles, especially sand, into aggregates
it reduces the cohesion (sticking together) of clay and silt particles
it increases the water-holding capacity of sandy soils
it supplies mineral ions, such as nitrates, sulphates and phosphates
it is the source of energy for the soil micro-organisms
it increases the productive capacity of soils.
Soil water
Soil water, from rainfall or irrigation, is needed for plant growth and for the soil organisms. It
may be present as a soil solution in the pore spaces or held as a film around tiny mineral particles
(adsorbed water). Figure 8.7 shows this. Dissolved mineral salts in the soil solution supply
essential nutrients for plants. After rainfall, the soil may be saturated with water. But following
drainage, the level will reach field capacity, which is the optimum water level for plant growth.
At field capacity the larger pore Figure 8.7 Soil water: spaces are filled with a continuous stream
of water capillary water and adsorbed which moves upwards by capillarity (capillary water.
water). This can be used by plants for photosynthesis. Excess water is lost from plants by
transpiration. If soil water is lost and not replenished, crop plants begin to will during the day but
regain their turgidity at nightfall. This is known as temporary wilting. It indicates that the soil
water level has decreased and that the plant roots cannot take up enough water to replace that
being lost by transpiration during the day. Turgidity is regained at nightfall because the
temperature drops, and less water is lost from plants by transpiration. If soil water loss persists
without replacement, the roots are unable to obtain any water so leaves and soft stems droop and
do not recover at night. This state is referred to as permanent wilting and can result in death of
the crop. Permanent wilting is an indication that the capillary stream of water in the pore space is
broken. Plant roots are unable to take up the adsorbed water which is held tightly round soil
particles.
Soil air
Soil air and soil water share the pore space together, and interchangeably, in the soil. The volume
percentage of air present in the pore space is referred to as the soil aeration. Following heavy
rainfall, as water drains through the soil, air moves into the larger pore spaces which were
formerly occupied by water. As the soil water continues to drain away or is used, soil air enters
the smaller pores. The composition of the soil air varies, depending on soil-water relationships
and the biological activities in the soil. Generally, in soil air:
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the moisture content is higher than in atmospheric air
the oxygen level is lower
the carbon dioxide level is higher.
The differences in levels of oxygen and carbon dioxide are due to the respiration of plant roots
and soil organisms.
In practical farming, soil aeration occurs when the farmer carries out tillage and drainage. Soil
aeration encourages the growth of plant roots. It also ensures there is enough oxygen for the
respiration of micro-organisms that bring about decomposition. In addition, aeration helps to
remove toxic gases.
25. Describe the physical and chemical properties of major soil types
The classification of soil types is based on the proportions of different-sized mineral particles
and the natural soil-forming processes. The sizes of the different mineral particles are included in
Table 8.2 on page 97.
It follows that:
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•
a clayey soil will contain a high proportion of clay particles
a silty soil will consist mainly of silt particles
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a sandy soil will have more sand particles than other types
a loam soil will contain about equal amounts of sand, silt and clay particles.
There are also other differences between soils. For example:
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gravelly soils contain large amounts of particles larger than 2 mm in diameter
alluvial soils are formed through the action of running water, which erodes rocks,
transports mineral particles and deposits them at a distance from the parent rock
colluvial soils have moved down the slope, or accumulated at the bottom of a hill as a
result of gravity; they are often gravelly
volcanic soils are formed from lava and volcanic ash
peaty soils are found in marshy areas and form due to the accumulation and partial
decomposition of organic matter
saline soils are found in coastal areas affected by sea water and contain high
concentrations of salt; these are of little value in crop production.
Physical properties of soil
Soil texture
Soil texture refers to the fineness or coarseness of the soil. It is determined by the proportion of
different sized mineral particles present (see Figure 8.8). For the farmer, soil texture is related to
the workability of the soil and how easy it is to plough. Some soils are 'light' as they are easy to
till (sandy soils), some are 'heavy' (clay soils), and others are 'intermediate' (loam soils). Soil
texture can be determined by three main techniques, which are summarised in Table 8.3.
Soil texture is important to the farmer because it affects the:
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holding capacity of air and water in the soil
ease and rapidity of drainage
total surface area of mineral particles available for chemical reactions to take place
workability of the soil, whether it is 'light' or 'heavy'
ease with which roots can penetrate
way in which crops respond to fertilisers.
Soil structure
Soil structure refers to the arrangement of the various particles, cemented together into clusters
(aggregates) which create a network of cracks and pores in the soil. Although aggregates may be
made up of similar types of particles, they generally differ in size, shape, particle composition
and arrangement, and stability. Aggregates contain pore spaces between their particles (intra-pore
spaces) and there are spaces between adjacent aggregates (inter-pore spaces).
The aggregates may form:
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lumps with a diameter greater than 1 cm
crumbs with a diameter from 5 to 10 mm
granules with a diameter of less than 5 mm.
Aggregates (see Table 8.4) are classified into four major types.
Factors affecting aggregate formation
The following all affect the ease with which aggregates form:
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Climate: the effects of wetting, drying, freezing and thawing.
Activities of soil organisms: fungal mycelia cement the soil particles together;
earthworms, termites, beetles and slugs burrow and mix soil particles; micro-organisms
decompose organic matter and form humus.
Organic matter accumulation and decay: the binding effect of humus.
Activities of plant roots: penetration, permeation, gum exudates and root decay.
Tillage operations: ploughing, rotovating, manuring and liming.
In practical farming, farmers recognise the importance of preparing and maintaining the soil in a
suitable physical condition for the cultivation of crops. Tillage will break up and mix the soil to
produce stable aggregates and a crumb structure called the tilth. A good tilth provides adequate
aeration, moisture, drainage and root-room for the crop.
Soil porosity and soil aeration
Soil porosity is the volume percentage of pore space in a lump of soil that is not occupied by
solid soil particles. It varies according to the soil type and the tilth. A porous soil allows:
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water to percolate into the soil and become trapped as a film around mineral particles
after drainage
air, containing oxygen, to enter the soil for the respiration of plant roots and soil
organisms
plant roots to penetrate and grow freely in the soil
soluble nutrients, from fertilisers and organic manures, to spread through the soil and
become available to plant roots.
Soil aeration is dependent on soil porosity and also on the amount of the pore space which is
occupied at any one time by soil water. Soil air and soil water occupy the same pore space and
the amounts of each will vary according to the conditions. A well-drained soil contains more air
than a waterlogged soil.
Soil temperature and soil organisms
In the Caribbean, temperature on the soil surface ranges between 23°C and 30°C. Within the top
15 cm of soil (the furrow slice), temperatures between 28°C and 30°C are the most favourable
for the soil organisms, biochemical processes and soil formation. Soil temperature is influenced
by sunlight, vegetation cover, soil cover (both natural and artificial), soil moisture and organic
matter content. All these factors, with the exception of direct sunlight, lower the soil temperature.
Soils that lack vegetation cover and which have little organic matter, lose moisture rapidly when
exposed to direct sunlight. Consequently, the soil temperature will rise.
Soil temperature affects:
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soil macro-organisms, such as earthworms, which are more actively burrowing when it is
warm
soil microbial activity which increases when warm and decreases when cold
roots of seedlings which are destroyed by high soil temperatures as plant cells dehydrate
due to evapo-transpiration.
germination of seeds which is more rapid under warm temperatures
soil caking and crusting which occurs as a result of high soil temperatures, direct sunlight
and rapid loss of moisture.
Farmers can lower soil temperature by mulching, cover cropping, intercropping, irrigation,
improving soil cover and incorporating organic matter into the soil.
Chemical properties of soil
Soil nutrients
Plants require 17 essential nutrient elements for their growth and development. These are shown
in Figure 8.9, overleaf. Fourteen of these are supplied by the soil. The others (carbon, hydrogen
and oxygen) come from air or water.
Nine of the elements are required in large quantities and are designated as macronutrients. The
others are only required in small amounts and are the micronutrients or trace elements. The
macro-nutrient elements are present in soils as ions and may be derived from the parent rock,
released from organic matter by the activities of soil micro-organisms, or added in the form of
fertilisers. For example, calcium and magnesium occur in limestone and dolomite. Dolomite is a
rock which is processed into dolomitic limestone and used as a liming material on acidic soils to
reduce the acidity. In Figure 8.9, three of the major nutrients are called primary elements. These
are nitrogen, phosphorus and potassium and can be supplied to crops in the form of inorganic
fertilisers (see Topic 8.6). Calcium, magnesium and sulphur are known as secondary elements.
Calcium and magnesium help to improve soil aggregation. This affects aeration and tilth in clay
soils. Sulphur, needed by all plants for protein synthesis, is obtained from rainwater, farm
manure or superphosphate fertiliser added to the soil. The roles of the major nutrients in crop
production are summarised in Table 8.5.
The micro-nutrients are only required by plants in very small quantities. If there is a deficiency,
indicated by poor growth of a crop, they can be supplied to the plants as foliar sprays (applied to
the leaves) or combined with other fertilisers and added to the soil.
Soil particle-soil nutrient relationship
Plants obtain soil nutrients from two main sources: the adsorbed nutrients on the surfaces of clay
and humus particles (colloids) and the dissolved minerals in the soil solution. These essential
nutrient elements are present in the form of ions: cations which are positively charged (K', Ca"
and Mg") and anions which are negatively charged (Cl-, SO4 and NO3). The uptake of ions by
the roots is not passive but requires energy from aerobic respiration. Soil particles, both mineral
and organic, are reservoirs of soil nutrient elements. These elements may be held in
combinations not readily available for plant nutrition and are released by physical, chemical and
biological processes. The rate of release is affected by environmental conditions in the soil. Table
8.6 summarises some soil minerals and their associated nutrient elements.
Leaching
Once nutrients have been released into the soil, they maybe lost through leaching— in this
process soluble substances are removed by water. The nature and size of the soil particles are
directly related to this loss of nutrients. For example, leaching is greater in soils made up of
coarse sand particles than in soils with finer particles, such as silt and clay. Potassium, a nutrient
found in most soils, is generally low in sandy soils due to leaching. Similarly, chemical reactions
and the exchange of soil nutrient elements are associated with the nature and size of clay and
humus particles. Clay and humus particles are very small, but they possess large surface areas
and negative charges which attract positive nutrient ions and water. Each particle is referred to as
a micelle or micro-cell and has a great capacity for attracting positively charged nutrient ions.
This attraction of nutrient ions to the surfaces of the clay and humus particles enables nutrients to
be held in the soil so that they are not removed by leaching.
Soil pH
The pH of the soil is a measure of the hydrogen ion concentration of the soil water. pH is
measured on a scale from 1 to 14. A value of 7 is neutral: values below 7 are acidic and those
from 8 to 14 are alkaline. The pH range for soils is from 3 to 10, but most tropical soils have a
pH value between 5 and 7.
Soils in limestone areas are slightly alkaline due to particles of calcium carbonate. Sandy soils
tend to be slightly acidic because the rain causes leaching of soluble ions which would otherwise
neutralise the acidity.
Acid soils are less fertile than alkaline soils because the acidity causes the mineral salts to be
more soluble and therefore more easily washed away by rain. When rainfall is greater than
evaporation, calcium, magnesium, and potassium ions are leached away from the topsoil as the
water moves downwards. The soil becomes more acidic because hydrogen ions replace the
calcium, magnesium, and potassium ions. In tropical regions, minerals that are less soluble in
water, such as aluminium, kaolinite and quartz, are left in the top layers of soil. Soil acidity can
be reduced by liming. The pH can be determined using Universal Indicator test strips. Farmers an
interested in the pH of the soil as certain crops favour a certain pH. If necessary, they can adjust
the pH to suit their crops.
26. Explain how major elements are recycled in nature
The carbon and nitrogen cycles are important in making carbon and nitrogen compounds
available for the activities of living organisms. Green plants are the producers, building up their
food supplies from carbon dioxide, water, and sunlight (photosynthesis) and also using mineral
ions from the soil. The consumers are the animals which eat both plants and other animals. The
decomposers in the soil, such as bacteria and fungi, break down the dead remains of other
organisms, releasing nutrients for plants to use again. Soil contains large numbers of microorganisms, many involved in the recycling of nutrients. Some of these organisms are shown in
Table 8.7. Bacteria and fungi are of vital importance in nutrient recycling.
The Carbon Cycle
The carbon cycle (Figure 8.10) shows how carbon and carbon compounds linked to natural
processes and products. Three processes underpin the carbo cycle: photosynthesis, respiration,
and decomposition.
During photosynthesis, plants take in carbon dioxide from the atmosphere and use it to
manufacture simple sugars (which are carbon-containing compounds); these are then built up
within the plant to make carbohydrates, lipids, and proteins. Animals and humans, as consumers,
eat the plants or plant products thereby taking carbon compounds into their bodies. All living
organisms require energy which is released from carbon compounds through respiration. Carbon
in the form of carbon dioxide is a waste product of respiration and is released into the
atmosphere. In the process of decomposition, waste products from crop residues, green manures,
animal urine and faeces, dead and decaying organisms are digested by micro-organisms. These
micro-organisms gain energy from the decomposition process and release carbon dioxide into the
atmosphere as a result of their respiration. Some carbon dioxide dissolves in soil water forming
carbonic acid, carbonates and bicarbonates of calcium, magnesium, and potassium. As these
compounds are soluble, they can be used by plants. Often, they are lost through leaching. When
carbon-containing fuels (wood, coal, petroleum, and natural gas) are burnt, carbon dioxide is
released into the atmosphere. Coal and petroleum come from plants which were buried millions
of years ago, so these fuels are referred to as 'fossil fuels'. The carbon cycle summarises the
circulation of carbon compounds in natural processes. It also enables us to understand some of
the causes of the 'greenhouse effect', which keeps the Earth warm. 'Global warming' results from
increasing levels of carbon dioxide in the atmosphere.
The nitrogen cycles
Nitrogen is essential for forming plant and animal protein. Figure 8.11 shows the nitrogen cycle.
Nitrogen as a gas makes up 79% of the Earth's atmosphere, but few organisms can use it in this
form.
How nitrogen in the air is made available to plants
During thunderstorms, lightning converts gaseous nitrogen to nitrogen oxides, which dissolve in
rainwater and get washed into the soil as nitrates. Plants can use nitrates and they absorb these
through their roots.
Atmospheric nitrogen is 'fixed' into nitrates by two different groups of nitrogenfixing bacteria
found in the soil. Rhizobium bacteria enter the roots of leguminous plants, such as peas and
beans, and causes nodules to form (see Figure 8.12). The bacteria live in the root nodules and
take up nitrogen gas and convert it to compounds of nitrogen which the plants can use to make
proteins. Other bacteria, such as Azotobacter and Clostridium, live freely in the soil. These
bacteria convert nitrogen to ammonium compounds, which can be used by some plants or
oxidised to nitrites and nitrates by other bacteria in the soil.
Nitrifying bacteria
The organic matter which comes from the remains of plants and animals, urine, faeces, crop
residues and compost, undergoes decomposition by bacteria and fungi in the soil and ammonium
compounds are formed. Under aerobic conditions, ammonium compounds are converted to
nitrites and nitrates by nitrifying bacteria. Nitrosomonas converts ammonium compounds to
nitrites and Nitrobacter converts nitrites to nitrates. The nitrates are then taken up by the plant
roots and built into plant protein.
Denitrifying bacteria
In anaerobic soil conditions, denitrifying bacteria obtain their energy by converting nitrates to
nitrogen gas, which escapes from the soil into the atmosphere. This is also a part of the nitrogen
cycle.
27. Explain the factors affecting soil fertility
Soil fertility refers to the productive capacity of a soil in which the soil conditions, nutrient
supply and availability are favourable for the growth of crop plants. A fertile soil has the
following characteristics:
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moderately porous with good aeration and drainage
retains adequate moisture
has a high organic matter content and is rich in nutrient elements
has adequate permeability for roots
is slightly acidic (optimum pH 5.5 to 6.5)
is relatively free from toxins, pests, and diseases.
Soil fertility is affected by climate, topography, the nature of the parent material, fertilisers, and
soil management.
Climatic factors
In the Caribbean, climatic factors determine the crops that can be grown and the livestock that
can be reared. When first colonised by Europeans, the main crops were those that would not
grow in Europe but thrived in the Caribbean. Sugar cane, coffee and cocoa were grown for
export. The climatic factors which determine where crops are grown are rainfall, temperature,
wind, and humidity.
Rainfall
Rainfall is seasonal and varied in its intensity. In the rainy season, prolonged rainfall results in
waterlogged soils which prevent tillage and also affect the soil organisms. Heavy rainfall causes
flooding in low-lying areas and there is erosion of soil, together with leaching of nutrients and
damage to crops and livestock. In the dry season, there is a lack of water, and it is necessary to
irrigate for crop production to be successful. Many areas, particularly flat islands such as Antigua
and Barbados, have low mean annual rainfalls and prolonged periods of drought. These dry
periods harm plants and reduce productivity.
Temperature
Most Caribbean countries are between 1 °N of the Equator and the Tropic of Cancer so the
climate is tropical with an average range of temperature between 22°C and 34°C (suitable for
year-round agriculture). Although most territories have hilly areas, there is not a great range of
temperature variation.
Wind
Since the Caribbean area is mainly made up of small island states, it is wind-swept and cooled by
sea breezes and the north-east trade winds. The winds mean that a uniform temperature is
maintained throughout any island, with occasional variations. However, the area is prone to
hurricanes with high winds and torrential rainfall.
Humidity
Humidity (a measure of the water content of the atmosphere) varies according to the seasons. In
the wet season, the humidity is high and in the dry season it is low. Humid conditions do not
affect soil fertility, but during periods of high humidity there is greater spread of fungal diseases.
Biotic factors
Agricultural activities impact on soil fertility, especially those practices which involve the
preparation, use and tillage of the land. In clearing land for crop production, it is poor practice to
burn natural vegetation as this destroys organic matter in the soil. The topsoil is exposed to
erosion and soil organisms, especially micro-organisms which bring about decomposition and
the formation of humus, are destroyed. Some agricultural practices, such as planting trees, help
to conserve topsoil, retain water in the soil and preserve the micro-organisms.
Topographic factors
Most Caribbean countries are hilly, and few have large areas of flat land. This affects soil fertility
in several ways. Soils on the slopes of mountains are shallow due to erosion and the most fertile
soils are in the valleys. Because accessibility is limited in hilly areas, farmers find it difficult to
till the soil and improve soil fertility. There are restrictions on the use of heavy farm machinery
in such regions, so effective land preparation cannot be carried out. Farming in the hilly areas is
limited to small enterprises.
The nature of the parent material
The parent material of soils consists of rocks which make up the Earth's crust. These rocks vary
in size from large masses to small fragments such as boulders, gravel, and stones. All rocks are
made up of inorganic minerals which have become consolidated and hardened geologically. They
become weathered physically, chemically, and biologically to form soils.
Types of rocks
Igneous rocks are formed from the cooling and solidification of molten rock. The major minerals
in these rocks are quartz, micas, and feldspars. Sedimentary rocks are formed from other rocks
which have been weathered, transported, and deposited at the bottom of swamps, lakes or seas
through natural forces. As a result of geological processes, heat, and pressure the material
becomes hardened into sedimentary rocks. The minerals normally found in sedimentary rocks
include sandstone, shale, and limestone. Metamorphic rocks result from changes which occur to
igneous and sedimentary rocks when they are subjected to intense heat, pressure and chemical
processes within the Earth's crust. In the case of sedimentary rocks, sandstone is changed to
quartzite, shale to slate and limestone to marble. Igneous rocks are changed to gneisses and
schists. The fertility of soils depends on the nature and sizes of the particles derived from the
rocks. Soils derived from limestone tend to be alkaline and those derived from sandstone are
usually acidic.
Land management
The way in which land is managed by farmers has an impact on soil fertility. Good management
benefits the soil and can bring about higher yields of crops. Good management practices include:
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agro-forestry and silviculture which conserve topsoil and water and also preserve the soil
organisms
application of fertilisers, organic matter and lime to improve the nutrient status of the
soil, maintain fertility and promote crop growth
efficient land clearing
avoiding the burning of vegetation
pruning, tillage, drainage, mulching, staking, cover cropping and planting shade trees on
pastures — all these improve the soil condition.
Agro forestry is a system of land use in which harvestable trees or shrubs are grown among or
around crops or on pastureland. Silviculture is the growing of forest trees.
Taking care with chemicals
The use of hazardous chemicals and the inefficient disposal of waste materials cause pollution of
water and soil. There is also a risk of these chemicals destroying the soil micro-organisms.
Inorganic and organic fertilisers
Inorganic fertilisers include sulphate of ammonia, nitrate of potash (saltpetre) and NPK
(consisting of nitrogen, phosphorus and potassium). These fertilisers are manufactured through
chemical processes. They are also known as artificial fertilisers.
Organic fertilisers are derived from plant and animal remains. Organic fertilisers are referred to
as manures or compost. They improve the structure, aeration and drainage of soils in addition to
supplying nutrients.
Both manures and inorganic fertilisers supply nutrients. The manures maintain and improve the
soil's structural properties and supply essential nutrients. The artificial fertilisers contribute a
concentrated supply of essential soil nutrients but do not affect the structural properties of the
soil.
Soil amendments describe substances such as lime, gypsum, sulphur, bagasse coffee-hulls,
manure and organic fertilisers which may be used to improve so properties. These substances
make the soil more productive, correct soil nuttier deficiencies and replace nutrient elements lost
through crop removal. The maintenance of soil fertility is described in Topic 8.10.
28. State the importance of minor nutrients in crop production
The minor nutrients are referred to as micro-nutrients or trace elements. They are important for
plant growth as they are found in many of the enzymes needed for cells to function properly. It is
not always easy to identify the effects of individual elements. For example, yellowing of leaves
could be due to a lack of magnesium sulphur, nitrogen or iron (see Table 8.8).
29. Interpret fertilizer ratio
Inorganic fertilisers can be simple fertilisers, supplying one of the major nutrient elements:
nitrogen, phosphorus or potassium. For example, urea provides nitrogen, single superphosphate
provides phosphorus and muriate of potash provides potassium.
What does fertiliser ratio mean?
Mixed or compound fertilisers provide two or more of these elements in a simple fertiliser ratio.
Low grade fertilisers contain less than 25% of the nutrient elements, medium grade contain
between 25% and 40% and high grade more than 40%. Manufacturers of fertilisers normally use
labels which indicate the percentage of nitrogen (N), phosphorus (P) and potassium (K), together
with the ratio of these three elements, on their fertiliser bags. Labelling indicates the type and
grade of fertiliser that is offered for sale, as well as the nutrient content and the nutrient ratio (see
Table 8.9).
From Table 8.9, we can see that some fertilisers have different percentages of total nutrients but
the same nutrient ratio. For example, NPK 5:10:5 and NPK 10:20:10 have the same nutrient ratio
but their total nutrient content is different. NPK 5:10:5 has a total nutrient content of 20%,
whereas NPK 10:20:10 has a total nutrient content of 40%.
Fertilisers with a higher nutrient content will cost more. So, while two fertilisers, such as NPK
20:10:10 and NPK 10:5:5 with the same nutrient ratio of 2:1:1, may be suitable for particular
crops, the rates of application must be adjusted because of the difference in their total nutrient
content. If NPK 10:5:5 at the rate of 500 kg per hectare is recommended for a particular crop and
the farmer only has NPK 20:10:10, then he will need to apply 250 kg per hectare as this fertiliser
has twice the total nutrient content of the NPK 10:5:5.
30. explain how soil fertility can be maintained
Keeping the soil in a fertile state is a challenge for farmers. Several methods can be used:
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soil amendments
cropping systems
soil and land management
irrigation and drainage.
Soil amendments
Soil amendments include any materials that supply ingredients and nutrient elements which
collectively improve soil structure and maintain soil fertility. They vary in type, but their main
functions are to improve soil structure, to increase water-holding capacity and permeability, to
supply nutrient elements, to ensure adequate drainage and aeration and to neutralise soil acidity.
Soil amendments include:
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manures
inorganic fertilisers
organic matter
liming materials.
Manures
Manures are also known as organic fertilisers and can be grouped as follows:
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pen manures are the partially decomposed solid materials derived from livestock pens;
consist of dung/droppings, bedding or litter; slurry from washing pens of dairy cattle and
other farm animals
compost manure derived from the leaf litter and crop residues
green manure refers to a green crop, preferably a legume, that is ploughed into the soil at
its flowering stage; adds nitrogen to the soil
guano from the droppings from birds; contains large amounts of nitrogen and potash
bonemeal made by grinding bones from meat processing companies; contains some
nitrogen but large amounts of phosphate.
Manures, such as pen, guano and compost, are spread evenly over ploughed land and rotovated
into the soil. If the manure is liquid, as in slurry, it is spread mechanically over ploughed land
and pasture using a slurry spreader.
Inorganic fertilisers
Inorganic fertilisers may be simple inorganic fertilisers, supplying one of the major nutrients, or
compound inorganic fertilisers, supplying two or more nutrients. Some examples of simple
fertilisers and the nutrients they supply are urea (nitrogen), muriate of potash (potassium), triple
superphosphate (phosphorus) and ammonium sulphate (nitrogen and it also lowers the soil pH).
Compound fertilisers usually contain the three major nutrients nitrogen, phosphorus and
potassium, and are referred to as NPK fertilisers. The ratios and percentages of these three
nutrients vary in different grades of NPK fertilisers (see Topic 8.8). There are several methods of
applying fertilisers, depending on the type of fertiliser, the area to be covered and the crop to
which it is being applied. For large-scale applications, the fertiliser is usually spread by
machinery, but on small farms it is done by hand.
Farmers need to determine the fertiliser requirements of their crops. To do this, several factors
need to be taken into consideration (see Table 8.10).
Methods of application depend on the:
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type, age and stage of development of the crop
system of planting: distance apart of rows; distance apart of plants
machinery and equipment available
availability of labour
weather conditions
Organic matter
Organic matter, other than manures and compost, may be used on soils to improve the waterholding capacity. Waste materials, such as bagasse from sugar cane processing, coffee-hulls and
sawdust, may be used for this purpose. Sometimes they are used as 'fillers' in fertilisers, where
they add bulk and serve as inert substances.
Liming materials
Liming materials are usually applied to acidic soils to reduce soil acidity, to increase calcium and
magnesium ions in the soil, to reduce the concentrations of iron, aluminium and manganese, and
to promote the activities of the soil micro-organisms. Lime may be added to the soil as:
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calcium oxide [CaO] referred to as quicklime or burnt lime
calcium hydroxide [Ca (OH) 2], known as slaked lime
calcium carbonate [(CaCO 3)], also known as chalk or ground limestone
•
calcium magnesium carbonate [CaMg (CO 3)] or dolomitic limestone.
Lime is usually applied to acidic soil during preparation of the land and before any crops have
been planted. Before it is done, the soil is tested in a laboratory to determine the recommended
rate of application. In the Caribbean, soil testing is carried out by the Ministry of Agriculture at
no cost to farmers.
The land to be limed is ploughed using a disc plough or a mouldboard plough. Lime is then
spread evenly over the ploughed area, at the recommended rate, either manually or mechanically.
Using a rotovator, the lime is mixed thoroughly within the top half of the furrow slice (7-10 cm).
Finely ground limestone applied during land preparation produces more speedy and effective
results. Dolomitic limestone is often preferred because it supplies both calcium and magnesium
to the soil.
Cropping systems
Cropping systems include crop rotation, cover crops, intercropping and multiple cropping (see
Chapter 12). The inclusion of deep-rooted, shallow-rooted, leguminous and cover crops in a
cropping system improves soil fertility by cycling nutrients between the upper and lower levels
of the soil. Leguminous crops encourage nitrogen fixation. Adequate vegetative cover reduces
the loss of soil and nutrients.
Cultural practices
The physical condition of the soil can be improved, and soil fertility maintained by tillage,
draining and irrigation where needed. Tillage maintains soil structure and contributes to the
aeration and drainage. It also makes it easier for roots to grow and incorporates organic material
into the soil. Adequate drainage is important in the wet season. In the dry season, the soil must
retain enough water for crop growth, and this may mean that some form of irrigation is necessary
(see Chapter 12).
31. describe the process of composting
Composting refers to the process by which organic matter (leaves, soft stems, rejected fruits and
vegetables) is decomposed to form compost manure. In making compost, several essential
components are required, and each has its specific function (see Table 8.11).
Making compost
To prepare compost, a suitable site needs to be chosen. It should be well-drained and close to the
garden or cropping area. The base of the composting area should be concrete and measure 4.0 m
long x 1.5 m wide. Instead of concrete, plastic sheeting could be securely pinned to the ground. It
is usual to divide the composting area into three equal compartments, each approximately 1.3 m
wide and 1.5 m long. The Phase 3 Section needs a protective cover to prevent loss of nutrients
through run-off and leaching. A shed is useful for storing composted material and to protect it
from rain. When construction of the composting area has been completed, all composting
materials should be collected and sorted. All bottles, plastic containers, stones and tin cans need
to be removed. Plants with hard woody stems are difficult to compost and it is a good idea to
remove nutgrass and weed plants with seeds.
The Phase 1 Section is then built up as follows:
•
•
•
•
•
•
a layer of starter material, consisting of pen manure, is placed on the base to a depth of 10
cm
a layer of organic matter is loosely arranged on top of the starter and built up to about 25
cm in thickness; both the starter layer and the organic matter need to be loosely arranged
to allow air to circulate
1.0 kg of sulphate of ammonia is broadcast over the organic matter layer
0.5 kg of ground limestone is spread evenly on top of this
alternate layers of starter and organic material (plus the fertiliser and limestone) are
stacked until a height of 1.5 m to 2.0 m is reached
the heap is watered and kept loose and moist. storage shed with compost manure.
After 3 to 4 weeks, all the materials in the Phase 1 Section are transferred to the Phase 2 Section,
making sure that the undecomposed materials that were at the bottom and sides of the old heap
are placed in the middle of the new heap. A suitable moisture level is maintained by watering
when necessary. The compost is left in the Phase 2 Section for a further 3 to 4 weeks, after which
time it is moved to the Phase 3 Section. The compost is left to decompose here for another 3 to 4
weeks. At the end of this period, the compost is transferred to the storage area and is ready to be
used on the garden or cropping area. During the decomposition of organic material, microbial
activity results in high temperatures which destroy parasitic organisms and some of the weed
seeds in the plant wastes. Once the material has been moved out of the Phase 1 Section, a new
heap can be built up in this section, following the same sequence. In this way, the farmer has a
continuous supply of compost to maintain soil fertility. The composting process described here is
suitable for situations where there is a lot of vegetable waste, and the farmer has a large enough
area on which to build a site and storage area. Smaller farmers and gardeners may use specially
designed plastic bins, which take up less space.
32. define soil erosion
Soil erosion is the process by which particles of soil are carried away from one area, by water or
wind, and deposited at another area. All soils undergo erosion, but if there has been no clearing
or cultivation of the land, the rate of erosion is slow and allows the processes of soil formation to
continue. If vegetation cover is removed, as when land is cleared for agriculture, forestry or
grazing, then the soil is exposed to wind and water. Soil erosion is speeded up and can become a
problem. Factors that control the amount of soil erosion are:
•
•
•
•
•
•
amount of rainfall
wind speed and intensity
the type of rock
the slope of the land
the amount and type of vegetation cover
the presence of grazing animals.
33. distinguish among different types of soil erosion
Soil erosion can be entirely due to natural causes, or it can result from human activities. Natural
soil erosion occurs in an undisturbed natural environment as a result of:
•
•
•
•
•
running water on steep slopes
running water on sloping areas with loose, friable soil
landslides of loose, saturated soil, perched on an impervious layer, in hilly or
mountainous areas
strong winds blowing over loose soil in dry, semi-arid or and (desert) areas
sea-waves pounding the land in coastal areas.
Accelerated soil erosion occurs as a result of the activities of human beings who disturb the
natural environment, creating soil conditions which speed up soil erosion by water and wind.
These activities include:
•
•
•
•
•
•
burning the vegetation on the land, including 'slash and burn' agriculture
overgrazing of pastures by livestock
deforestation (the cutting and removal of trees)
mining and quarrying operations • creating bare soil patches on the land by overweeding
or brush cutting too closely
lack of ground cover, such as a cover crop or a mulch
unsuitable cultural or soil conservation practices on hilly terrain.
34. explain the causes of soil erosion
Water In the Caribbean, soil erosion by water is a problem during the rainy season.
Wind
Wind can also cause soil erosion. Strong winds can cause soil creep, which is the gradual
movement of loose soil particles, such as sand, on the soil surface towards the opposite direction
from which the wind is blowing. Saltation of soil particles occurs when strong winds cause loose
soil particles to leap suddenly, become airborne for a while and then eventually fall to the
ground, forming heaped areas of soil. Where mining, quarrying and land preparation operations
are carried out under dry soil conditions, soil particles in suspension are transported by winds
and may be deposited many kilometres away. Soil particles in the atmosphere can cause
respiratory problems in people and in farm animals.
Burning
Burning vegetation as part of land clearing has positive and negative effect Among the positive
effects are:
•
•
•
unwanted material, such as cane-trash, is burnt out, so canecutters work more efficiently
land clearing can be carried out more speedily
harmful plants, such as nettles, are destroyed
•
•
•
harmful animals, such as snakes, scorpions, centipedes and the nests of wasps are
destroyed
the ashes on the land add potash to the soil
the soil is sterilised as a result of the intense heat
However, burning vegetation is not recommended as it creates smoke pollution i the atmosphere.
It is recommended instead that harmful plants and crop residue are cut and stacked in an area
where they can decompose slowly. Other negative effects of burning vegetation are:
•
•
•
•
•
•
the destruction of organic matter which took many years to accumulate
humus in the soil is also destroyed
soil organisms are killed
the soil surface becomes bare with no plant cover, so it is more exposed to soil erosion
soil water is lost more rapidly through evaporation
leaching of nutrients can occur more readily.
Animals
Any bare land exposed to heavy rainfall can lose nutrients through leaching and mineral particles
from run-off. The effects of animals, through grazing or trampling can leave soil bare and open
to erosion, particularly in the rainy season.
35. explain soil and water conservation methods
Soil conservation refers to protecting the soil from erosion and maintaining i fertility. It is of
great importance to agriculture in the Caribbean region.
Cultural practices which conserve the soil
Cultural practices play a vital role in preventing soil erosion and maintaining soil fertility.
Minimum tillage is where soil is only cultivated to provide the planting hole and rows for the
crops. It does not expose soil to rainwater and can therefore reduce erosion in hilly and
mountainous areas. Ridging is where ridges are built across a slope to prevent the rapid flow of
watt downhill, and it can reduce soil erosion and help to retain water in the soil. Organic matter,
such as mulches or weeds that have been uprooted and If lying on the soil, will reduce the direct
impact of rain drops and allow water to filter slowly down into the soil. A mulch is a protective
covering over the soil surface, usually of organic matter. Rotational grazing helps to conserve
pasture, because the animals are moving around, and the formation of bare patches is avoided
(see page 243).
The importance of vegetative cover
Vegetative cover (see Figure 8.18) refers to a layer of vegetation covering the surface of the soil.
Vegetation is used to prevent soil erosion and includes the following practices:
•
the planting of cover crops, which grow and spread rapidly, providing a protective
covering on the ground (legumes are often used as cover crops)
•
•
•
•
contour cropping where crops are cultivated along the contours of sloping land
strip cropping where deep-rooted and shallow-rooted crops are cultivated in strips,1 to
1.5 m wide, across a hill slope (this is very similar to contour cropping)
grass barriers (normally included in a strip cropping system); the grass is planted in line
with the contours of the land; the fibrous roots of the grass grow in thick clusters and
bind the soil particles together
grassed drains using matted grass, such as Savanna or Bermuda, which is grown, cut and
kept low in box drains dug across or down gentle slopes.
Forests and soil conservation
Forests are very important in soil management and water management. The roots of trees and
forest plants grow in thick clusters, binding soil particles and controlling soil erosion. The leaf
litter that builds up provides a thick layer of organic matter on the soil surface, covering and
protecting the soil and reducing evaporation. This organic matter is then decomposed by soil
micro-organisms and nutrients are released into the soil. The activities of other soil organisms
mix upper and lower layers of the soil so that nutrients are cycled. The forest canopy provides
shade and helps to control the drying out of streams. The planting of forest trees in mountainous
regions can control soil erosion and forests may be established as windbreaks in areas where the
soil is loose and liable to wind erosion. Sometimes forest trees are cultivated amongst food
crops, such as banana, cassava, citrus and avocado (this is an example of agro forestry). The trees
stabilise the soil, providing vegetative cover and shade. In arid and semi-arid areas, wind erosion
is a major problem and the most common method used to conserve the soil is the construction of
windbreaks. Rows of trees are planted along the edges of cultivated areas. The trees slow down
the speed of the wind and prevent large amounts of sand or soil being blown away to other areas.
Terracing and contour ploughing
Terracing involves the construction of relatively flat strips of land along the contours of a
hillside, forming a number of steps which are sometimes referred to as bench terraces. The broad
banks of earth prevent water running down the slope, controlling soil loss and soil moisture. On
gentle slopes, contour ploughing is practised. Land is cultivated along the contours, preventing
water flowing downhill. Before contour ploughing or terracing, the farmer needs to establish the
contour lines. This can be done using a simple A-frame and marking the lines with stones or
sticks (see page 346).
Water conservation and soils
With a climate that has a rainy season and a dry season, water conservation is essential on most
Caribbean farms. Farmers depend on water storage systems, drains and dry farming techniques.
Water storage systems
Water storage systems used by farmers may include tanks, ponds, pools and wells. Storage tanks
can be made of galvanised iron, concrete reinforced with steel or rotoplastic (pvc). Water-holding
capacity varies, and a farmer may have three or more large tanks each holding 4500 litres,
depending on the nature and size of the farm. Ponds and pools are normally constructed in the
dry season, so that they are ready for the onset of the rainy season. Often, fish are reared in ponds
providing another source of income for the farmer. Wells can be dug out (from 3 to 10 metres in
depth). The water comes from underground springs and the height to which it rises depends on
the water table.
Gabions are cages of wire mesh, filled with soil, rocks or sand. They are used in constructing
dams, retaining walls, or directing the flow of flood water. They have advantages over other
methods of construction as they can be arranged in various ways, are resistant to being washed
away, and drain freely. In a gabion weir, the mesh baskets are arranged to form a channel down a
slope.
Drainage
Drainage channels are dug around fields and plots. These can drain away excess water in the
rainy season and be used for irrigation in the dry season. Contour drains are constructed across
the hill slope, along the contour, to prevent the rapid flow of water downhill.
Dry farming techniques
Dry farming techniques include any technique which conserves water or prevents the
evaporation of too much water from the soil surface in the dry season. These techniques include
minimum tillage, mulching, use of manure and compost and cover crops. Controlled irrigation
(using manual systems, hoses, or sprinklers) may be used to water crop plants in the dry season.
Land Preparation
36. explain the relationship between climate and agricultural production
The fertility of the soil has a great influence on the types of crops that can be grown and the crop
yield. As we have seen in Chapter 8, the climate in the Caribbean has affected the soil types and
the maintenance of soil fertility. An alternation between dry seasons and wet seasons means that
farmers must be aware of the climatic conditions when deciding what to grow, where to grow it
and how to prepare the land.
The Caribbean climate
Most Caribbean countries have a tropical marine climate, with warm temperatures all year round.
This type of climate occurs on tropical islands in equatorial regions situated between 5° and 25°
north and south of the Equator. In the Caribbean, the Atlantic Ocean and the Caribbean Sea are
warm at all times of the year. The average temperature is around 27°C, but there are variations
depending on the season. For example, in Jamaica the average temperature is 27°C in July and
24°C in January. There is a rainy season from May to October and the rest of the year is
relatively dry. During the rainy season, the northern and eastern sides of mountainous islands get
most of the rain. The southern and western sides can be dry, as they are sheltered from the
prevailing trade winds. In Dominica, which has mountain peaks, there is an annual rainfall of
7600 mm, whereas in Barbados, which is flatter, annual rainfall is around 1500 mm. The rainy
season coincides with the summer hurricane season. Hurricanes are very violent storms. They
can occur at any time from June to November but are most frequent during August and
September. They usually develop over the ocean in the eastern Caribbean during the summer,
when the surface temperature of the sea is high and air pressure falls below 950 millibars. Wind
speeds of 120 to 250 km per hour occur and there is extremely heavy rainfall. Hurricanes cause
structural damage to property and crops, as well as flooding.
The effect of rainfall on plants
Due to the warm temperatures, plants that thrive in tropical conditions grow quickly and
germination is rapid. Rainfall, its amount and when it occurs, has a much greater effect on
agricultural production than temperature. During the rainy season, it is important that the ground
does not become waterlogged, so efficient drainage is essential. in the dry season, irrigation is
needed for those crops that do not tolerate dry conditions. Some crops, such as cocoa and
bananas, need 2000 mm of rainfall annually, distributed throughout the year, if they are to grow
successfully. Other crops, such as sugar cane, corn, and rice, need most rainfall during the
growing season. Sugar cane, in its early growing period between May and August, requires
heavy rainfall. This needs to be followed by long periods of sunshine to increase the sugar
content of the cane.
Forecasting the weather
Farmers need to know about the climatic conditions of the area they are cultivating so that they
can grow crops that are suited to the soil and climate. With better long-term weather forecasting,
it is possible to predict changing weather patterns so that harvesting, planting, and spraying can
be carried out at suitable times. Hurricane warnings are given on the radio and television several
days in advance. About 36 hours before a hurricane is due, a hurricane alert is issued, and people
are warned to take precautions. Farmers try to ensure that their buildings areas safe as possible
and that their livestock are protected.
37. measure rainfall and temperature
Measuring rainfall
Rainfall totals are recorded every month (this is the total amount of rain which has fallen in a
month). Information gathered over many years can show the seasonal pattern of rainfall for an
area. The information in Table 9.1 indicates that there is a wet season from May until October
when a dry season begins.
Using a rain gauge
Rainfall is measured using a rain gauge. This apparatus consists of:
•
•
•
a large outer cylinder made of tin or copper
a funnel with a small opening
a jar in which the water is collected.
In addition, a measuring cylinder is needed to measure the collected rainwater. The outer
cylinder is placed in the ground, partly buried, to make it stable. It should be in a flat, open space
away from trees and tall buildings which could affect the amount of water getting into the gauge
(from splashing or from run-off). The funnel fits closely to the top of the outer cylinder and
water passes through into the collecting jar. The jar is emptied every 24 hours. The quantity of
water is measured using the measuring cylinder and is then recorded in mm.
More modem electronic gauges, which measure and record the rainfall automatically, are now
used in most weather stations. A simple type of gauge can be set up using a beaker or a
measuring cylinder, but the measurements will not be accurate as water will be lost due to
evaporation.
Measuring temperature
Temperature is a measure of how hot or cold something is. It is measured using a thermometer,
which consists of a glass tube containing a liquid. The liquid expands when the temperature rises
and contracts when the temperature falls. Sometimes the liquid used is alcohol containing a red
dye, but many scientific thermometers use mercury. The glass tube is calibrated so that the
temperature is easy to read off. Scientific temperature measurements are made using the Celsius
scale, where 0°C is the temperature at which water freezes and 100°C is the temperature at which
water boils. For recording climatic temperature data, it is usual to use maximum and minimum
thermometers. The maximum thermometer records the highest temperature reached during the
period of measurement and the minimum thermometer records the lowest temperature. Inside
each of the glass tubes of the thermometers, there is a small piece of glass called an index.
The maximum thermometer contains mercury and when the temperature rises, the mercury
pushes the index upwards. When the temperature falls, the index is left behind and the maximum
temperature reached can be read by looking at the lower end of the index and reading the figure
from the scale.
The minimum thermometer contains alcohol. The alcohol expands as the temperature rises and it
rises up the tube, flowing past the index. When the temperature falls, the alcohol contracts, and
the index is dragged down the tube. To read the minimum temperature, the position of the end of
the index closest to the edge of the alcohol is used.
When readings have been taken, the thermometers need to be shaken to restore the index to the
level of the fluid.
The Stevenson Screen
If temperature comparisons between different areas are to be made, then thermometers have to be
kept in standard conditions. For this purpose, the thermometers are kept in a Stevenson screen. A
Stevenson screen has the following features:
•
•
•
•
•
it is painted white to reflect the sunlight
it has louvred sides allowing air to flow freely around the instruments
it should have a double roof; the air space created is a poor conductor of heat and the
effect of the heat from the sun will be less
it is located on a grassy surface well away from trees and buildings
it should stand 112 cm above ground level to decrease the effect of heat conduction from
the ground.
Stevenson screens often contain other recording instruments, such as wet and dry bulb
hygrometers to measure humidity.
38. interpret weather records
The measurements made by meteorologists are used to forecast weather, either on a short-term
basis or over longer periods. Short-term forecasts are usually made for periods of 5 to 7 days, but
weather patterns can change quickly, and farmers should check the forecast on a daily basis,
particularly if considering harvesting or planting.
Observations are collected by the Caribbean meteorological organisations and farmers obtain
weather reports using the internet, radio, and television. Certain symbols, recognised
internationally, are used to indicate the weather on maps. Some of these are illustrated in Figure
9.4. Interpreting symbols on weather maps is relatively straightforward. The symbols for rainfall
and wind speed indicate the quantity and nature of the rainfall expected and the severity of the
winds.
Fronts
A front form where different air masses meet. The symbols for fronts indicate the boundaries
between air masses that have different properties. The Caribbean is affected by two air masses:
•
•
the polar air mass which originates in Canada and the USA in winter and moves
southward to the Caribbean
the tropical maritime air mass consisting of warm, moist air in the Gulf of Mexico and
the Caribbean Sea.
Where the cold air mass meets the warm air mass, there is a cold front at the edge of the polar air
and a warm front at the edge of the tropical air. When cold air meets the warm, moist Caribbean
air, it causes the warm air to rise. The warm air is cooled, condensation takes place and rain
clouds form. As a result, there is heavy rainfall, thunderstorms, the temperature decreases and the
wind changes speed and direction. This type of weather is called the Northers because it
originates from North America.
As the cold air mass continues to move southwards, it becomes warmer until eventually there is
little difference between the temperatures of the two air masses. Under these conditions, the cold
air mass does not move much, the weather conditions are more stable, and a quasi-stationary
front is established.
The ITCZ
When two major air streams (the Northeast Trades and the Southeast Trades) meet, rain and
thunder showers are produced. This happens because the air of the Southeast Trades is cooler
than that of the Northeast Trades and causes the warmer air to rise and bring about the wet
conditions.
Where these two air streams meet is called the Intertropical Convergence Zone (ITCZ). This
zone moves northwards during the northern summer, bringing heavy rain to Trinidad and Tobago
from June to August. During winter in the northern hemisphere, the wind systems shift south of
the Equator and from January to May areas north of the Equator have their dry season.
39. use weather records in farming decisions
Effects of heavy rain
During the wet season, nutrients are lost from the soil by leaching. In order to maintain the
fertility of the soil, farmers have to add fertilisers and manure, together with using cultivation
methods such as rotation of crops. Application of fertilisers has to be timed to avoid heavy
rainfall and fit in with the growth of the crop. A farmer would be wasting money if he added
fertiliser when heavy rainfall was due — much of it would be leached.
Heavy seasonal rainfall floods low-lying areas and this can disrupt farming activities. For
example, if heavy rains come at the end of the sugar cane harvesting season, then it becomes
difficult to use heavy machinery. The fields are muddy, the soil is churned up and the crop may
be spoilt. To overcome this problem, extensive drainage schemes have been set up in areas that
are likely to be flooded. Often, drainage channels can serve two purposes: removal of excess
water in the rainy season and irrigation in the dry season.
Effects of temperature
Although warm temperatures favour plant growth, they also encourage the decomposing microorganisms that are involved in the breakdown of organic matter in the soil. Plant and animal
remains are broken down quickly and the humus content of the soil in warm areas is often low.
In Chapter 8, the importance of organic matter and the maintenance of soil fertility were
described; farmers are encouraged to use manure and compost as part of the regular treatment of
their land.
Warm temperatures also encourage pest organisms, such as aphids and mites, which damage
crops and cause diseases in animals. The use of pesticides and other control methods has to be
fitted into the farming operations. The weather forecast, together with a knowledge of the life
cycle of the pest, can help the farmer decide on the best time to spray the crop or remove the
disease-affected plants.
Hurricanes
The seasonal patterns of weather are more or less predictable each year: there will be a rainy
season and a dry season. Farmers can fit their operations to this cycle of weather. The one feature
that is less predictable is the occurrence of hurricanes and tropical storms. The hurricane season
extends from June to October, but during that time there may be few hurricanes or many and
their severity can vary. Hurricanes can destroy buildings, infrastructure and communications as
well as disrupting the production of crops and the rearing of livestock. However, there are
warning systems and because the Caribbean lies in the path of such weather systems, most
farmers are aware of the dangers and take precautions.
40. evaluate land preparation methods
Land preparation ensures that the soil is well-prepared before a crop is planted. It involves
clearing, tillage, fertilising the soil, liming, drainage, levelling the land and bed formation.
Clearing
Clearing the land is normally the first operation. Depending on what the land was previously
used for, it usually involves removing trees, bushes and shrubs, tall grasses, or crop residues.
Areas that had been abandoned and may have become overgrown with trees and dense foliage
may be cleared manually, using an axe or a cutlass, or mechanically with a chainsaw and a
bulldozer.
Clearing land of grass, bush and crop residues is done by brush cutting. This can be done
manually, using a brushing cutlass, or mechanically, using a weed wacker or a brush cutter
attached to a tractor. When land is bulldozed it is essential to save the topsoil. The sequence
when clearing land is:
•
•
•
•
trees are removed and heaped in windrows
topsoil is scraped off and placed in heaps
land is graded, filling in any depressions
topsoil is then spread over the entire area.
Tree trunks and twigs, which have been chopped or bulldozed, should be placed in windrows
(heaps), and allowed to decompose; in this way organic matter, humus and nutrients are released
into the soil.
Tillage
Tillage refers to breaking up the soil surface and incorporating organic matter into the soil. It is
usually divided into two stages: primary tillage, where the soil is broken up by ploughing, and
secondary tillage which involves the refining of the soil. In primary tillage, land which has been
cleared is either dug manually with a garden fork or ploughed mechanically using a tractor. The
tractor may be a hand tractor with a rotary plough or a four-wheeled tractor with a mouldboard or
disc plough.
The effect of primary tillage is to:
•
•
•
loosen or break up the soil surface
allow air and water to enter the soil more freely
bury or mix organic matter with the soil.
At the end of primary tillage, the soil is in large clods or lumps.
Secondary tillage refers to breaking up large clods of soil into smaller pieces (or aggregates) and
the production of a tilth. The process may be done manually, using a hoe, rake, or cutlass, or
mechanically using a harrow and a rotovator.
The effect of secondary tillage is to:
•
•
•
•
obtain a tilth suited to the crop
produce a seedbed for the cultivation of crops
cut up and mix organic matter (crop residues or stubble) into the soil
allow the roots of crop plants to penetrate easily and grow freely in the soil.
Farmers use two main methods of tillage, either manual or mechanical.
Drainage
It is essential to provide drainage for the removal of excess water from the surface and subsurface of the soil, especially during the rainy season. There are many types of drains and
drainage systems. These range from simple channels to complex systems which can also provide
irrigation during the dry season (see Figure 9.10). The preparation of drains may be done
manually, using a fork, spade, hoe, rake, and garden line; or drains can be dug mechanically
using a ridger/banker (see Figure 9.9) and a backhoe.
Some common types of drains: box drain, V (vee) drain, trench/canal/storm drain, tile drain
(underground), rubble drain (underground) and contour drains (on hillsides).
Levelling and making beds
After drains have been dug, the land needs to be levelled to form beds suited to the crop, soil
type, the season or weather conditions. During the dry season, flat-topped beds may be used, but
in the rainy season the beds need to be constructed so that excess water is removed, especially in
areas with clay soil. Cambered beds have slightly sloping tops. Ridges and furrows create
channels for water to drain away and mounds have raised portions in the centre. The farmer may
use a variety of beds: cambered beds, ridges and furrows, mounds on cambered beds and ridges
and furrows on cambered beds.
Examples of beds: flat-topped beds, cambered beds, ridges and furrows, mounds on cambered
beds, ridges, and furrows on cambered beds,
41. discuss the importance of machinery in crop husbandry
A machine may be defined as:
•
•
an instrument or device used for carrying out a task
any equipment or apparatus, specially designed for a particular purpose and used for the
transmission of force, power or motion to produce a desirable effect.
In agriculture, several types of machines are used for tasks such as ploughing, planting,
harvesting, plucking, ear-notching, and castrating. New machines are continually being designed
and existing machines are re-designed and improved.
Seeders
Seeders, otherwise known as planters, may be of various types. Some consist of drills, which
sow seeds directly on to the soil. Sometimes drills combine seeds and fertilisers, so that the seeds
are planted with an appropriate fertiliser for the crop. Transplanters are machines which plant
seedlings such as tomato, sweet peppers, or rice, or they may plant bulbs, tubers or corms.
The advantage of a seeder is that the seeds are planted evenly and at the required density. This is
a more efficient method than broadcasting the seed. The machines that can transplant seedlings
speed up the operation, saving time and the cost of manual labour.
Harvesters
There are various types of harvesters, each designed to harvest a specific crop. These machines
speed up the process of gathering in a crop, saving time and manual labour.
The simplest types are those which can be attached to a tractor, such as the sweet potato
harvester. This machine digs the tubers, lifting them from the soil on to a conveyer belt.
Combine harvesters are used for grain crops, such as rice and other cereals. This type of
harvester is self-propelled and cuts, threshes and winnows the grain, which is then gathered in
trailers and transported away for storage. Sugar cane can also be harvested by special combine
machines.
Tractors
The tractor is one of the most useful pieces of farm machinery. It is mainly used for pulling
ploughs, harrows, cultivators, and trailers, and for transmitting power (by means of the powertake-off shaft) to attachments (brush cutters, rotovators, fertiliser spreaders and threshers).
Tractors are built for use in different environmental situations and purposes.
Therefore, tractors will vary in:
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•
•
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size
horsepower (hp) or kilowatts (KW)
mode of mobility: wheels or tracks
price, including resale value.
Crawler tractors are more powerful than wheeled tractors and have metal chain belts on
sprockets, instead of wheels and rubber tyres. They are suitable for land clearing operations, site
preparation for roads and buildings and the construction of dams and embankments (levees).
They are used where land is damp and slippery, covered in tree stumps and stubble and not
suitable for the four-wheeled tractor. These machines are expensive, have high maintenance costs
and require skilled operators. Many farmers find it more economical to hire such equipment
when it the functions of a harrow. is needed for a specific purpose, rather than investing in a
machine which might not be used all the year round.
Tractor attachments
Tractor attachments are devices that fit onto tractors. They make agricultural operations easier,
saving time and labour. Table 9.4 summarises the main uses of each attachment. Harvesters and
seeders may be attached to tractors. These have been described earlier in the chapter.
42. describe the care and maintenance of simple tools and equipment
Tools and equipment should be well-maintained so that they will:
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be in good condition when needed for use
remain serviceable
last for many years.
Major practices for the maintenance of tools and equipment are summarised in Table 9.5.
Keeping records
It is essential to keep records of tools and equipment. Such records
should include:
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an inventory of all tools and equipment on the farm
date purchased and cost
any tools loaned, together with the name of the borrower, date
borrowed, and date returned, the condition on return
any regular maintenance, such as safety checks.
Maintaining a knapsack sprayer
A knapsack sprayer is a manual farm machine used to spray pesticide
mixtures on to crops. It consists of:
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a tank to hold the pesticide
an adjustable lance with a pressure relief valve to avoid spraying above target pressure
a nozzle attached to the end of the lance for spraying the pesticide
a pump operated by a pumping handle • a contoured frame with padded shoulder straps
and adjustable waist band.
To use the equipment, chemicals are poured into the tank and the tank cover is screwed on
securely. Air is pumped into the sprayer tank, using the built-in pumping device. The nozzle cap
is adjusted to give the desired size of droplets. The sprayer can then be used to spray the crop
thoroughly. It is best to avoid spraying on a very windy day and protective clothing should
always be worn. After spraying, the following procedures should be carried out:
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the residual air pressure should be released from the sprayer tank using the air pressure
release valve
any unwanted chemical mixture should be emptied out of the tank and disposed of in a
hole in the ground
the sprayer tank should be washed out with detergent
the filter should be checked for any chemical particles which may block the nozzle
clean water should then be sprayed through the system
the sprayer should be dried and any parts requiring grease should be lubricated
the sprayer and chemicals should be stored in a cool, well-secured area.
43. describe the safety precautions in the operation of tools, machinery, and equipment
In agriculture, safety practices are very important in the handling of tools, equipment, machinery,
fuels, pesticides, and other chemical substances.
Tools and equipment
Each tool or piece of equipment is specially designed for carrying out a particular agricultural
operation. It is therefore important to choose the tool or equipment best suited to the task: using
the wrong tool can be hazardous. The following safety practices should be followed:
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ensure the tool or piece of equipment is in good condition, with any handles firmly
attached, blades or prongs clean and sharp, and moving parts oiled or greased
wear the correct safety gear: tall rubber boots, goggles, gloves, coveralls, hard hat where
appropriate; avoid dangling straps or belts
control the equipment when chopping, digging, cutting, brush cutting or weeding
focus on the task while operating the equipment; stop if distracted
place equipment down safely when not in use; sharp tools should be stuck upright in the
soil so that they are clearly visible, or placed flat on the soil with their prongs or sharp
edges facing downwards
avoid laying tools or equipment on pathways or on heaps of weeds, where they could
cause injury or be forgotten.
Safety gear
Special safety equipment protects both the operator and the machinery. It may consist of special
gear for use with equipment or safety devices on the machinery.
Safety gear includes:
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clothing: coveralls which are tough, durable, and fireproof
head gear: hard hat and helmet, often with face shield
boots: steel-tipped, with non-skid soles
gloves: leather, fabric, disposable
safety glasses, goggles
respirators and face masks: offer protection from fumes, smoke, and dust
earmuffs: protection from loud noises.
Machinery and equipment may be fitted with safety devices such as:
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safety clips, buttons, bars
shields, guards, filters
safety fuses
colour-coded lights
an automatic shut-off which stops the equipment if there is a malfunction.
Safety and tractor operations
The tractor and its attachments should be in good condition. Any attachment must be safely
hitched with protective shields and safety guards in place. The driver needs to be trained and
wearing appropriate clothing (hard hat, steel-tipped boots, no dangling clothing, straps, or belts).
He should adjust the seat so that it is comfortable, and all controls can be reached easily, and
make sure that the rear-view minor is also adjusted. It is important to be aware of slippery areas,
slopes, proximity to services (gas, electricity, and water mains), farm animals, children and pets.
When the operation has been carried out, the engine should be switched off and the hand brake
applied before adjusting or removing any attachments.
Handling fuels and chemicals
Most fuels used on the farm are combustible and care has to be taken when they are handled,
used, and stored. Gasoline, dieseline and kerosene are used to power tractors, water pumps and
generators. These fuels should be stored in special containers approved by the Bureau of
Standards. There should be 'no smoking' and 'no naked flame' signs in the storage areas and in
areas where the fuels are handled. Storage areas should be fitted with locks. Chemicals, such as
artificial fertilisers and pesticides, should be handled with care and stored in a locked room.
Protective clothing should be worn when these chemicals are being used and all containers need
to be thoroughly washed after use.
Plant Morphology and Physiology
44. describe the external and internal structure and functions of plants
To cultivate crops, a farmer needs to understand plant structure. Crops can be grown for their
leaves (lettuce), leaf stalks (celery), stems (sugar cane), roots (carrots), flowers (cauliflowers),
fruits (bananas) and seeds (coffee). Different crops have different requirements and growth
patterns, so a farmer needs to consider the types of crops best suited to the environmental
conditions of the area.
Plant classification
Plants may be classified according to their major group, family, life cycle or growth habit.
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Major group: seed plants, sometimes referred to as flowering plants, produce both
flowers and seeds; they are further subdivided into monocotyledons and dicotyledons.
Family: monocotyledons and dicotyledons can be divided up into smaller groups which
have many features in common, e.g., peas and beans belong to the family Leguminoseae.
Life cycle: some plants germinate, grow, flower, seed and die, completing their life cycle
in one growing season or in one year (these are the annuals, such as lettuce, peas, corn,
tomatoes); some take two growing seasons or two years (biennials, such as carrot, celery,
radish, beetroot); others continue to grow, flower and produce seeds for many years
(these are the perennials, such as citrus, mango, cocoa, coffee).
Growth habit: herbs are plants with soft, non-woody stems, usually less than 2 m in
height (parsley, bodi beans, coleus, balsam); shrubs have stiff, woody stems, produce
branches close to the ground and grow to heights of less than 5 m (West Indian cherry,
guava, hibiscus); trees are tall woody plants with a well-defined trunk and branches at
some distance from the ground (mango, breadfruit, cedar, teak and mahogany).
Monocotyledons and dicotyledons
Monocotyledons, usually referred to as monocots, and dicotyledons, referred to as dicots, are
made up of a root system and a shoot system. They can be distinguished by the structure of their
seeds, arrangement of their flower parts, root systems and the shape of their leaves. A
comparison of the two groups is given in Table 10.1.
Plant structure
flower: contains reproductive parts
leaf: takes in carbon dioxide; absorbs light for photosynthesis
stem: supports leaves and flowers; transports water and minerals
root system: provides anchorage. takes up water, takes up minerals
The root system is below the ground and the shoot system is above ground. The root system
provides anchorage and takes up water and mineral ions from the soil. The shoot system supports
leaves and flowers, transports water from roots to leaves, and transports food made in the leaves
to other parts of the plant. The flowers contain the reproductive structures and produce fruits
which contain seeds.
Roots
There are four main types of roots:
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tap roots consist of a main, or tap, root with lateral roots growing out to the side (e.g.,
tomato, mango)
fibrous roots consist of a cluster of roots growing from the base of the stem (e.g., coconut
palm, corn)
adventitious roots grow from the base of stem cuttings (e.g., croton) or from leaves (e.g.,
Bryophyllum)
aerial roots grow above ground (e.g., Ficus, Philodendron).
Dicot roots
The internal structure of a young dicot root is made up of four types of tissues:
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epidermis: a single layer of cells on the outside of the root; cells in young roots have
outgrowths forming root hairs; function is to protect the young root and to absorb water
and mineral ions
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cortex: many unspecialised thin-walled cells, called parenchyma tissue; forms the bulk of
the young root; the cells have spaces between them (intercellular spaces)
endodermis: a single layer of cells separating cortex from vascular tissue; the cells
control movement of soluble materials between cortex and vascular tissue
vascular tissue: a cylinder at the centre of the root.
The vascular tissue is made up of several different types of cells (see Table 10.2).
Stems
Stems can be soft and non-woody (herbaceous) or woody. Herbaceous stems are often green and
carry out photosynthesis, but woody stems are covered in a layer of bark which is waterproof.
Monocots have non-woody stems, but dicot trees and shrubs have woody stems. The stems of
most plants grow upright, but some have underground stems called rhizomes. Cacti have stems
which are modified for storage of water.
Dicot stem
A dicot stem is made up of the same tissues as the root, but they are arranged differently:
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the epidermis has stomata (openings through which exchange of gases occurs during
respiration and photosynthesis)
there is no definite endodermis
vascular tissue is in separate bundles arranged in a circle around a central region of cells
forming the pith
cambium tissue is located between the xylem and the phloem in each vascular bundle.
Monocot stem
The arrangement of tissues in a young monocot stem differs from a dicot stem:
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the vascular bundles are scattered throughout the stem
there is no distinction between the cortex and the pith
there is usually no cambium between the xylem and phloem in the vascular bundles.
Leaves
A typical leaf consists of:
• a leaf blade, or lamina, which is the flat part
• a leaf stalk, or petiole, which attaches the leaf to the stem
• a midrib, or main vein, consisting of the transporting tissues
• a network of smaller veins.
The tip of the leaf is called the apex. The edges of the leaf are referred to as the margin.
The leaves of monocots (e.g., grasses) are long and thin with no definite midrib, but with parallel
veins. The leaves of dicots vary in shape and arrangement, with a midrib and a network of
smaller veins.
Simple leaves have a leaf blade that is not divided, but the margin may be smooth (cashew),
serrated (hibiscus) or lobed (castor oil). In compound leaves, the blade is divided into leaflets
attached to the leaf stalk. The leaflets may be arranged like the fingers on a hand (palmate) or in
a row either side of the midrib (pinnate). Examples are shown in Figure 10.7.
Leaves may be modified for food storage (fleshy leaf bases in onion), for protection (outer scale
leaves of onion), and for extra photosynthesis (flattened leaf bases of Acacia). Internally, leaves
are made up of epidermis, mesophyll, and vascular tissues (see Table 10.3).
Figure 1: dicot
The arrangement of the tissues in a monocot leaf (e.g., grasses) differs from that in a dicot leaf:
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there is no palisade mesophyll
there is less distinction between upper and lower epidermis
there is no definite midrib.
Seeds
A seed contains the embryo which will develop into a young plant. It also contains a store of
food for the embryo. A seed is surrounded by the seed coat or testa. Dicot seed The broad bean
seed is an example of a dicot seed. It has these external features:
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the testa, which protects the embryo and the food store
the tiny hole, called the micropyle, through which water enters before germination can
occur
the scar (hilum) showing where the seed was attached to the pod.
If the testa is removed, you can see two cotyledons, or seed leaves. The embryo consists of the
radicle, which grows into the root of the seedling, and the plumule which develops into the shoot
system. These features are shown in Figure 10.9.
Monocot seed
A monocot seed, such as the maize grain in Figure 10.10, differs from the broad bean seed:
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the outer protective coat is formed from fusion of the testa and the fruit wall as the maize
grain is a one-seeded fruit
there is only one cotyledon
the food store, called the endosperm, is separate from the cotyledon.
45. explain the processes of sexual and asexual reproduction in plants
Sexual reproduction
The flowers of seed plants contain the organs of sexual reproduction. Most flowers, such as
guava, contain both male and female parts in one flower and are called hermaphrodite. But other
plants, such as pumpkins, produce separate male flowers and female flowers on the same plant.
Parts of a flower
A typical flower has the following parts:
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a flower stalk, or pedicel attaches the flower to the stem
a receptacle: the swollen tip of the pedicel to which all the other floral parts are attached
a whorl (ring) of sepals, called the calyx: often green; protects the other flower parts
when in a bud
a whorl of petals, called the corolla: usually brightly coloured to attract pollinating insects
the male parts of the flower, called stamens: each consists of a filament, or stalk, bearing
anthers in which the pollen grains containing the male gametes are formed
the female parts of the flower, called carpels: each consists of a receptive surface, the
stigma, attached to the ovary by the style; the ovary contains ovules in which are the
female gametes, or egg cells.
Male flowers have all the above parts except the carpels. Female flowers lack stamens.
The ovules, which are the potential seeds, are inside the ovary. Depending on the species,
flowers may have one or more carpels and the number of ovules in each carpel may vary. The
number of stamens varies, and their location and size depend on the method of pollination.
Pollination
Pollination is the transfer of pollen from the anthers to the stigma. The pollen may be transferred
from the anthers to the stigma of the same flower or to another flower on the same plant; this is
known as self-pollination. Or pollen may be transferred from the anthers of one flower to the
stigma of another flower on a different plant of the same species; this is known as crosspollination. Pollination is essential for the production of economic crops, such as cereals and
fruits. Increased pollination leads to increased yields, which results in higher incomes for the
farmers. Cross-pollination is used in plant breeding to increase the vigour of a species and to
produce plants which are more resistant to pests and diseases. Farmers are encouraged to place
beehives in their orchards and to avoid excessive use of insecticides during the flowering period
of crops. These measures increase the chance of cross-pollination. Pollination can be brought
about by birds, other small animals, and humans, but the main agents are wind and insects.
Wind-pollinated flowers and insect-pollinated flowers show adaptations to their mode of
pollination (see Table 10.4).
Fertilisation
Fertilisation is the fusion (joining) of a male gamete with a female gamete to form a zygote,
which develops into the embryo. After pollination, pollen grains germinate on the surface of the
stigma and pollen tubes grow down through the tissues of the style to the ovary. At the tip of
each pollen tube are three nuclei: two male nuclei (the male gametes) and a pollen tube nucleus.
When the pollen tube reaches an ovule, the tip releases the nuclei. One male nucleus fuse with
the egg cell (female gamete) in the ovule to form the zygote. The second fuses with nuclei in the
ovule to form food storage tissue. The zygote develops into the embryo.
Seed formation
After fertilisation, seed formation occurs. The fertilised egg develops into the embryo of the new
plant. Food, made by photosynthesis in the parent plant, is stored in the endosperm tissue. In
some seeds, such as peas and beans, the food store develops in two cotyledons which become
swollen. In other seeds, such as castor bean and maize, food is not stored in the cotyledons, but
remains as a separate tissue. The tissues which surrounded the ovule in the ovary become the
seed coat.
Asexual reproduction
Asexual reproduction refers to the propagation of plants by means of vegetative parts and does
not involve gametes. Asexual reproduction can be achieved by natural methods, e.g., tubers,
suckers, and rhizomes, or artificially by cuttings, budding, grafting and tissue culture.
Natural methods of asexual reproduction
Several crops produce vegetative parts (see Figure 10.12) which farmers use as planting
materials. A farmer can grow bananas from banana suckers, yams from yam tubers and eddoes
from eddoe corms. These vegetative parts are referred to as organs of perennation; they store
food, enabling the plant to survive in a dormant state during the dry season and to resume growth
when conditions become favourable (see Table 10.5). Many of the plant parts used in natural
vegetative propagation are also eaten by humans and other animals (e.g., potato tubers).
Artificial propagation
The main methods of artificial propagation are:
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cuttings, e.g., cocoa, guava
layering, e.g., rose, lime
budding, e.g., orange, avocado
grafting, e.g., mango
tissue culture, e.g., orchid, banana
Cuttings
Cuttings are pieces of stem, root, or leaf, taken from a plant and given the right conditions for
growth. They contain cells capable of dividing and producing new tissues. After cuttings have
been taken from the parent plant, they need to be kept in suitable conditions of humidity, light
and temperature. High humidity prevents cuttings from drying out, so they are usually kept in a
propagator. Types of stem cuttings (pieces of stem from which new plants will grow) are listed in
Table 10.6.
Stem cuttings are usually taken from plants early in the morning, when plant cells are turgid (full
of water), and then wrapped in a moist tissue. Before planting in a propagator with a suitable soil
mixture, the base of each cutting is trimmed with a sharp knife, the leaves removed or partially
trimmed if necessary, and the base dipped into a rooting hormone which encourages growth of
roots. The soil is watered, and the propagator placed in suitable conditions of light and
temperature. The soil and atmosphere around the cutting are kept moist. Some stem cuttings,
such as sugar cane, cassava, and sweet potato, are planted directly into the field plots as they
produce roots easily. Root cuttings are pieces of root from which new plants will grow. They are
taken when parent plants are not actively growing, just before the rainy season. In the
propagation of breadfruit, lengths of root 10-13 cm long are taken, a sloping cut is made at the
lower end, and the cutting is pushed into the rooting medium with the top at soil level.
Layering
In layering, a young branch of a parent plant is encouraged to produce adventitious roots by
making an incision in the branch, bending it down and covering it with soil. Two techniques are
used: tongue layering and air layering. Adventitious roots are roots which form from a section of
the plant which is not underground. Tongue layering is carried out on plants that have spreading
branches close to the ground:
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a suitable branch 5-8 mm thick is selected
the leaves are removed from the area to be layered
a diagonal cut is made into the middle of the stem on the underside of the branch
the branch is held down in position on the ground by a wooden peg.
Roots form after 14-21 days. The newly layered plant can be cut from the parent and transferred
to a pot in a garden nursery.
In air layering, a young stem 7-8 mm thick is selected and leaves removed from the area to be
layered. The stem is cut into, and a portion of the bark removed over an area 3-5 cm long.
Rooting hormone is applied to the cut area, moist moss is placed around it, and it is then wrapped
up with polythene sheeting and tied securely. Roots develop after 14-21 days. The newly layered
plant is then cut from the parent and transferred to a pot for nursery treatment.
Budding
Budding is a form of grafting in which a single bud (the scion) from one plant is inserted into the
stem of another plant (the stock). The stock plant is rooted and may be of the same species as the
scion, or a related species. To carry out patch budding you need to:
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remove leaves from the selected area of the stem of the stock plant
lift a rectangular area of bark from the stem of the stock plant 20-30 cm from the tip
choose a plump and healthy bud on the scion and carefully cut and lift off a similar size
of bark around it
place the scion material on to the stock plant
apply a fungicide to the area
apply tape to the budded area leaving the bud exposed
place the stock plant with its new bud in a cool area and water regularly.
The terminal bud of the stock plant can be removed to encourage the growth of the scion.
Sometimes an inverted T-shaped cut is made in the bark of the stock plant and the bud is inserted
into the cut. The scion is taped to the stock as before to secure and protect the bud. This method
is commonly used for propagating citrus plants.
Grafting
in grafting, the scion consists of a piece of stem with several buds on it. It is inserted into the
stem of the stock plant with the cut surface of the scion in direct contact with the cut surface of
the stock, so that the tissues of the two plants grow together. For grafting to be successful, the
scion and the stock have to be related: either different varieties of the same species or belonging
to closely related species. Grafting is used in the propagation of mango, avocado and sapodilla.
The two types of grafting are:
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side or veneer grafting: the scion is inserted into a cut made on the side of the stem of the
stock; the scion is 5-8 cm in length and fits snugly into the cut on the stock; the two are
taped securely together
top or cleft grafting: the top of the stock plant is cut off; a wedge-shaped cut is made and
the scion is inserted; the two are taped together securely.
Tissue culture
Tissue culture is an artificial method of plant propagation in which a piece of plant tissue, such
as stem, leaf, or root, is cultured in a growing medium consisting of agar, nutrients and plant
hormones to produce new plants. The technique requires sterile, controlled conditions and can
result in large numbers of identical plants, called clones. Orchid, banana, and pineapple plants
can be mass produced in this way.
46. relate sexual and asexual reproduction to crop production
Sexual reproduction and crop plants
Sexual reproduction results in fruits and seeds, so it is vital in the production of rice, maize,
cereals, and fruits of all kinds. The production of seeds is also necessary if the farmer is to grow
other crops as most of our leaf and root vegetables are raised from seed. In the past, the farmer
would allow some of his crop to produce seeds, which were kept for planting the following year.
Nowadays, the farmer buys seeds from a seed merchant, expecting a high percentage to
germinate and grow.
Asexual reproduction and crop plants
Growing some crops from seed (e.g., fruit trees) takes a long time and the plants that result is not
always 'true to type'. In such cases, vegetative means of propagation can be used so that the
offspring are genetically identical to the parent plant.
Some plants, such as banana, pineapple, and breadfruit, do not produce viable seeds — these are
often propagated artificially (see Table 10.7).
The rhizomes of ginger, saffron and arrowroot can be cut into sections and, provided that each
section has at least one lateral bud, new plants can result. Bulbs, such as onions and garlic,
produce offset bulbs which are then separated and planted. Stem tubers of Irish potato are used to
produce new plants and yam tubers can be made to form buds which produce shoots.
47. describe conditions necessary for germination of seeds and growing of seedlings
A viable seed is one which is able to germinate and develop into a seedling. Seed viability is
usually expressed as a percentage. It refers to the total number of seeds expected to germinate
when 100 are sown. Seeds kept in sealed containers and cool storage conditions maintain their
viability over an extended period. A germination test can determine the viability of any batch of
seeds, especially if they have been loosely stored for a long time. Most packets of seeds carry
information on the expected percentage germination, so that the purchaser or farmer can decide
how many seeds to plant and the density of planting.
Germination
Germination refers to the process in which the embryo inside the seed grows and develops into a
seedling, using food stored in the cotyledons or endosperm. For germination to occur, seeds
require three main conditions: water, air containing oxygen and a suitable temperature (see Table
10.8). In addition, most seeds germinate more readily in darkness (although some need light). In
practice, many farmers create semi-dark conditions, using palm leaves or saran netting to cover
seed boxes and seedbeds. The covering gives protection from seed-eating birds but needs to be
removed as soon as germination starts to prevent pale weak seedlings.
Some seeds with very hard seed coats may be scarified to speed up germination. Scarification
involves making scratches in the seed coat, so that water can be taken up more readily and
germination can start. Farmers use different techniques, including scratching seed coats with a
sharp and pointed instrument, blowing seeds against a rough surface, or rubbing the seeds on
sandpaper.
Epigeal and hypogeal germination
There are two main types of germination: epigeal germination and hypogeal germination. In
epigeal germination, the cotyledons come above the ground as the seedling grows; in hypogeal
germination, the cotyledons remain below the ground. To understand the differences, look at the
embryo in Figure 10.17. Identify the epicotyl, the region between the plumule and the
cotyledons; then identify the Figure 10.17 An embryo plant. hypocotyl, the region between the
radicle and cotyledons. The two types of germination are compared in Table 10.9.
Germination of maize
The germination of monocot seeds, such as maize, is slightly different in that the food store is in
the endosperm. The cotyledon remains in the seed and absorbs food from the food store,
transferring it to the growing embryo. The radicle emerges and grows into the soil. The plumule
sheath (coleoptile) grows upright and appears above the ground. The plumule emerges from the
coleoptile, forming the first set of true leaves. The cotyledon remains below the ground.
Sowing seeds and seedling production
In crop farming, seedlings are produced using two major systems: container systems and seedbed
systems.
Container systems
Various containers can be used to raise seedlings: seed boxes, Speedling trays, plastic bags,
plastic cups, discarded cans and plastic bottles. For large-scale production of seedlings in
containers, it is usual to use seed boxes or Speedling trays. Any containers should be provided
with holes for drainage before being filled with a potting soil mixture. Commercially produced
potting soil mixtures, such as Promix (made up of peat moss, perlite, vermiculite, and dolomitic
limestone) can be purchased. However, a mixture can be made up using local and available
materials. Such a mixture would contain:
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3 parts topsoil or clay
3 parts pen manure
1-part sharp sand
1 part rotted coffee hulls, bagasse, sawdust, coconut fibre bast or compost
500 g dolomitic limestone per cubic metre of topsoil
30 cm3 of soil insecticide (Diazinon) and 10 g of fungicide per 4.5 litres of water.
Soil should be steam sterilised or treated with a soil sterilant (methyl bromide). The constituents
of the potting soil mixture ensure that it has a fine tilth, is rich in plant nutrients and well-aerated,
retains adequate moisture and will drain freely. The addition of insecticide and fungicide,
together with the sterilisation, will ensure that it is free from pests and weeds. Ideally, the
mixture should have a pH of 6.0 to 6.5.
Seed boxes, otherwise known as nursery boxes, are used for sowing seeds, pricking-off (thinning
out) seedlings and raising young crop plants.
A typical seed box is 35 cm long, 25 cm wide and 7 cm deep, and constructed of wooden laths
nailed together. At its base, there should be 5 mm wide slits for drainage. A box this size can
accommodate 35 seedlings. It is light to handle and can be re-used for several batches of
seedlings. Before sowing seeds, a thin layer of straw should be placed on the base to prevent
potting soil from falling through. Sifted potting soil is placed in the box to a height of I cm from
the top, levelled off, firmed with a pressboard, and then watered.
Seedling trays are commercially made and are now more widely used than seed boxes. The trays
are made of expanded polystyrene (styrotex), 75 cm long, 35 cm wide and 7 cm deep, divided
into compartments. They can be filled with potting soil mixture and one seed is usually sown in
each compartment so thinning-out of seedlings is not required. The seedlings become well-rooted
and are easily lifted out for transplanting. As with the seed boxes, trays can be re-used for several
batches of seedlings.
The advantages of container systems are that:
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the seedlings are cared for in a nursery
it is more convenient to handle and transport the seedlings
the seedlings become well-rooted in the potting soil medium
development of the seedlings is more vigorous as they have more space, root room and
nutrients
each seedling can be transplanted with a ball of soil (pillon) around the roots
most containers can be re-used for further seedling production.
Seedbeds
Seedbeds are useful for the production of seedlings for field crops, such as rice, cabbage, tomato,
and sweet pepper, requiring a large number of plants. They are established close to the field plot,
making it easy to transplant the seedlings and saving time, labour, and transportation costs. The
nature of the seedbeds depends on the crop. For example, a seedbed for cabbage seedlings needs
to be cambered and well-drained, but for rice seedlings the area should be bunded (have
embankments) to retain water.
A typical seedbed is 3 m long and 1 m wide, cambered for surface drainage and surrounded by
box drains for sub-surface drainage. The soil should be manured and have a fine tilth. When
preparing a seedbed:
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the area should be brush cut and cleared of grass and bush
plough with a hand tractor or garden fork
refine the soil to a fine tilth using a rotovator, hoe or rake
dig box drains
level the soil and camber
add pen or compost manure to a depth of 2-4 cm
add NPK fertiliser (10:15:10) at the rate of 30 g per square metre (30g/m2)
mix manure and fertiliser with the top 4 to 8 cm of soil
level the soil and remove large pieces of organic matter with a rake
apply a mixture of insecticide and fungicide.
Methods of sowing seeds
Methods of sowing depend on the container, the number to be planted and the nature of the
seeds.
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Seeds may be scattered or broadcast by hand, getting the distribution as even as possible.
They are then covered with a thin layer of potting soil or Promix.
Seeds may be sown in shallow drills made by a dibber in the soil surface. A thin layer of
potting soil or Promix is used to cover them.
Very tiny seeds can be mixed with water or sand before sowing. For example, tobacco
seeds are mixed with water in a watering can and applied to the soil as a fine spray.
Celery seeds may be mixed with sand and then either broadcast or sown in drills.
If Speedling trays are used, seeds are planted singly in the compartments. A small hole 12 cm deep is made with a dibber, the seed is placed inside and then covered with potting
soil or Promix.
The nursery
A nursery is where young plants are housed while being reared for transplanting into field plots.
The main features of a nursery should include:
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a steel or wooden construction so that it is sturdy
a graded concrete floor for efficient drainage
a roof covered with transparent polythene, so that light can enter but the seedlings are
protected from rain
saran netting placed on the windward side to protect seedlings from wind damage
concrete stands for seed boxes, Seedling trays and containers.
Thinning-out
Thinning-out gives each seedling more space for growth. It also reduces competition for light,
water, and nutrients, so that growth is more vigorous. If seedlings are spaced, they can be lifted
out with a pillon (ball of soil around the roots) when transplanting. In thinning-out, or 'prickingoff', seedlings are carefully removed from their original container or seedbed and transferred to
another prepared container. The newly thinned-out seedlings need to be protected from direct
sunlight and rain.
Looking after seedlings
In the nursery, seedlings need to be watered regularly, using a watering can with a fine rose.
Weeds should be removed by uprooting or using a dibber, and the soil surface broken up to
prevent compaction and to increase aeration. Fine pen manure or liquid manure can be applied to
the soil surface after it has been broken up. To control pests and diseases, seedlings should be
inspected at regular intervals and treated with insecticides if necessary. Seedlings may be
attacked by a fungus that causes a disease called 'damping off', where the stems are weakened,
and I topple over. The disease can be controlled by aerating the soil, controlling the watering, and
applying a fungicide to seedlings and soil twice weekly.
Transplanting
Before transplanting, seedlings should be gradually exposed to sunlight over a period of 7-10
days. This is called hardening and helps to strengthen the young plants so that they can withstand
full sunlight by the time they are transferred to field plots. Transplanting is carried out early in
the morning, late in the evening or when it is cloudy to:
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protect the seedlings from the scorching sun
reduce the wilting which may occur at transplanting time.
The field plot is prepared by digging holes for the seedlings, using the recommended spacing,
and placing pen or compost manure into each hole. The soil of the containers is watered, and the
seedlings are removed, each with some soil around the roots. Each seedling is placed in its
prepared hole, ensuring that it is not planted too deeply, and the soil is gently firmed around it so
that it stays upright. Seedlings should be watered after transplanting: this reduces wilting and
settles the loose soil, bringing soil particles in closer contact with roots.
Stages of plant growth During the life of a plant, there are two main stages of growth: the
vegetative stage and the reproductive stage. The vegetative stage involves:
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growth of the zygote into the embryo, the embryo into the seedling, and the seedling into
a mature plant
rapid increase in cell division, cell enlargement and differentiation into specialised tissues
and functions
rapid increase in plant size and weight
much branching and leaf development.
In the reproductive stage:
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the general increase in plant size slows down and development of new branches and
leaves occurs
flowers, fruits, and seeds are produced, continually or seasonally, until the plant dies.
These stages are illustrated in Figure 10.27.
48. explain the role of photosynthesis, respiration, transpiration, absorption, translocation,
photoperiodism and phototropism
Photosynthesis
Photosynthesis is the process by which plants manufacture carbohydrates (sugars and starches) in
their leaves, using carbon dioxide from the air and water from the soil, in the presence of the
green pigment chlorophyll and under the influence of light.
The chemical and word equations which summarise photosynthesis are given below.
Chemical equation: 6H2O + 6CO2 → C6H12O6 + 6O2
Word equation: water + carbon dioxide → glucose (carbohydrate) + oxygen
Photosynthesis is affected by carbon dioxide concentration, light intensity, temperature, and soil
water supply.
The sugars manufactured during photosynthesis are used by the plant in the following ways:
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in the process of respiration to release energy for cell division and growth
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to form starch, which is stored in leaves and other storage organs, such as tubers and
seeds
in the manufacture of proteins and lipids which are essential for the formation of cells so
that the plant can grow in height and girth, developing stems, leaves, and reproductive
structures.
Respiration
Respiration is the process by which sugar is oxidised or broken down, releasing energy for
growth and development. It is the opposite of photosynthesis: photosynthesis involves building
up molecules which store energy; respiration involves breaking down molecules to release
energy. The chemical and word equations which summarise respiration are given below.
Chemical equation: C6H12O6 + 6O2 → energy + 6CO2 + 6H2O
Word equation: glucose + oxygen → energy + carbon dioxide + water
Energy is stored in molecules of adenosine triphosphate (ATP) which can be used in the cells.
The energy released is essential for cellular activities such as: the formation of new cells
resulting in the growth of the plant
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maintaining the activities of existing cells
moving mate rials throughout the plant.
Transpiration
Transpiration is the process by which plants lose water in the form of water vapour through
stomata on their leaves and green stems. Stomata are small holes which occur on the leaves or
green stems. Transpiration results from the uptake and transport of water through the plant from
roots to leaves. The loss of water as water vapour is affected by environmental factors such as
sunlight, temperature, wind, humidity, and soil-water content. Water is essential for plant growth
because:
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it keeps cells turgid, resulting in the rigidity of leaves and soft stems
it transports mineral ions around the plant from the roots to the leaves
it is needed for photosynthesis.
The loss of water vapour from the leaves exerts a 'pull' on the column of water. This 'pull'
extends from the roots, through the stem and up to the leaves. The column is referred to as the
transpiration stream. There is also a cooling effect on the leaves as water evaporates from cells.
Wilting
If transpiration exceeds absorption of water by the plant and soil water is in short supply, then
cells lose their turgor and wilting occurs. This may be temporary at first and can be reversed if
water is supplied, but permanent wilting results in death. Repeated temporary wilting in crop
plants causes a reduction in cell division, poor development of tissues, stunted growth, and poor
yield.
Absorption
Cells need to take up water, mineral ions, and food substances. Cells also must get rid of waste
mate rials. To get in or out of cells, all substances need to pass through the cell membranes.
Movement through cell membranes can occur passively by diffusion, or actively in a process
requiring energy. Absorption of water is essential for photosynthesis, respiration, and
translocation. All these processes are inter-related and contribute to plant growth and
development. Any factor which hinders absorption of water will affect growth and development.
If plants cannot absorb sufficient water, then wilting occurs.
Diffusion
Diffusion occurs when molecules move from an area where they are in high concentration to an
area where their concentration is lower. Diffusion will continue until the concentration
everywhere is the same. No energy is required for this to happen.
Osmosis
Osmosis is used to describe the diffusion of water across a partially permeable membrane from a
dilute solution (with a high concentration of water molecules) to a more concentrated solution
(with a lower concentration of water molecules). Plant roots take up water from the soil solution
by means of their root hairs. The concentration of the soil solution is more dilute than the cell
sap, so water molecules pass from the soil solution into the root hair cells. This is an example of
osmosis taking place. Water then moves in a similar way across the cortex of the root into the
xylem vessels. The movement of water occurs along a concentration gradient.
Active transport
Mineral ions are transported from the roots to other parts of plant and used by the cells.
Sometimes mineral ions enter the roots by diffusion. If there is a higher concentration of mineral
ions in the soil solution than in the cell sap of the root hair cells, ions will diffuse from the soil
solution into the root hair cells. However, if the concentration in the cell sap is higher than in the
soil solution, ions may be taken up by active transport. This process requires energy to move the
ions against the concentration gradient.
Translocation
Translocation is the process by which water, mineral ions and food substances are transported in
specialised tissues within the plant. The specialised tissues are:
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the xylem, composed of vessels and tracheids: transports water and mineral ions
the phloem, composed of sieve tubes and companion cells: transports food substances in
solution.
Translocation may take place upwards: water and mineral ions from the soil move through the
xylem to the leaves; or soluble food substances move from storage organs to growing points,
buds, flowers, and fruits. Food materials manufactured in leaves (sugars) are translocated
downwards to the lower parts of the plant and to storage organs. There is also some radial
(sideways) transport of water and food materials from the xylem and phloem to surrounding
tissues. Translocation is important for growth as it supplies the nutritional needs of plant cells,
helps to maintain turgidity, and is necessary for the development of storage organs.
Phototropism
Phototropism is a growth movement made by a plant in response to the direction of a light
stimulus. If the tips of plant shoots are exposed to a light source, they will bend and grow
towards the light. This is an example of positive phototropism. It benefits the plant as it in
seedlings. places the leaves in the best position for photosynthesis. Usually, plants respond by
bending their stems in the direction from which the light is greatest. This can l: clearly seen if
seedlings are kept for some time on a windowsill.
Photoperiodism
Photoperiodism refers to the influence of day length (duration of light) on the production of
flowers. In temperate countries, there is some variation in t number of daylight hours due to the
winter and summer seasons. In the trop and the Caribbean, the variation in hours of daylight is
not as great, but the effects can still be seen in some plants. Based on the effects of day length on
growth and flowering, plants can be divided into three groups (see Table 10.10).
In the Caribbean, artificial techniques are used to bring certain short-day plants, such as
poinsettias and chrysanthemums, into flower around Christmas time when they are in demand.
The plants are kept in the vegetative state by keeping them in long days, and then induced to
flower by exposing them to shorter day lengths.
49. discuss the effects of environmental factors on plant growth and development
Growth is a characteristic of all living things. It can be defined as an increase in the size of a
plant. Development refers to changes in form and function which occur during the different
stages of growth. Plant growth and development are affected by environmental factors — these
should be taken into consideration before crop production is undertaken.
Understanding environmental factors, together with the experience of advisors, can assist
farmers in choosing crops which are suitable for their land. It is not possible to change the
climate, but understanding weather patterns and soil fertility can result in better crops.
Rainfall
Rainfall provides water for essential plant processes. Excessive rainfall results in waterlogged
soil which slows plant growth. An absence of rain also damages growth — plants may wilt and
die without enough water. When considering which crops to grow, thought must be given to
drainage and irrigation.
Temperature
Temperature controls the rate of metabolic activities in plants. Effective growth is promoted by
cool to moderate temperatures. If the temperature is too high, metabolic activities in plants are
increased and the food energy that is left for growth and development is reduced. If the
temperature is too low, metabolic rate slows and growth is reduced. In the Caribbean,
temperatures do not vary greatly, but shade should be provided for young seedlings in warm
weather.
Sunlight
Sunlight is essential for photosynthesis, which results in food for growth and development. If
plants are grown in the dark, they produce long, slender stems and unexpanded leaves. They lack
the green pigment chlorophyll, so cannot carry out photosynthesis and die when their food
reserves are used up. Such plants are referred to as etiolated and the condition is called etiolation.
The direction of the light affects the growth of shoots (phototropism). Also, the length of the day
affects vegetative growth and flowering in some plants (photoperiodism).
Sunlight also affects transpiration. Plants under shade lose less water through transpiration than
those in sunlight. As a consequence, these plants produce leaves that are well-expanded.
Soil fertility
Soil fertility is important so that plants can obtain the necessary nutrients for growth. Soils with
low fertility hamper growth and development, resulting in low yields. Soil fertility can be
managed in a number of ways (see Chapter 8).
Pests and diseases
Pests and diseases limit growth and development. Before planting, a farmer might treat the soil
with pesticides and fungicides and remove weeds. Once the crop is planted, regular inspection is
needed to detect the first signs of an infection or infestation so that treatment can be applied.
Plant Genetics, Breeding and Biotechnology
50. explain the basic principles of genetic inheritance in plant breeding
Understanding how characteristics of organisms are passed from generation to generation is
fundamental to the techniques used in plant breeding. For thousands of years, farmers have
selected crops and livestock with the most favourable characteristics and used these to produce
crops with greater yields and to breed better animals. This process was known as selective
breeding, and it produced results in a relatively short time. Nowadays, we can change the
characteristics of crop plants by introducing new genetic material. This can improve yields,
confer resistance to disease and increase the nutritional content of the crop. The basic structure of
all organisms is the cell. Some organisms, such as bacteria, are unicellular and consist of only
one cell. Most organisms are multicellular and consist of large numbers of different cells
organised into tissues and organs.
Cells
All cells have the following features:
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a cell membrane surrounding the living material of the cell
the cytoplasm: the living material of the cell
a nucleus containing chromosomes.
Plant cells (see Table 11.1) differ from animal cells in that they have:
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a cellulose cell walls
a large vacuole (space surrounded by a membrane) containing cell sap
chloroplasts containing the green pigment chlorophyll.
Cell division
New cells are formed by cell division, during which first the nucleus divides and then the
cytoplasm divides. It is vital that genetic information in the parent cell gets passed on to the new
cells. There are two types of nuclear division:
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mitosis: in mitosis chromosomes in the nucleus of the parent cell are divided into two
equal sets so that the nucleus in each new cell has exactly the same number of
chromosomes as the parent cell; this type of division occurs when new cells are produced
throughout the life of a living organism
meiosis: this involves the formation of gametes (sex cells) in the reproductive organs; the
nucleus of each gamete has half the number of chromosomes as the parent cell; when
fertilisation occurs, the zygote has the correct number of chromosomes restored.
Mitosis
When a cell is not dividing, it is impossible to see the detailed structure of the nucleus. The
chromosomes are present as very long strands of deoxy ribonucleic acid (DNA). Just before the
cell divides, these long strands get shorter and fatter: they form structures (chromosomes) which
can be seen when cells are viewed using a light microscope. Each chromosome consists of a pair
of identical chromatids joined by a centromere. The genes are located on the chromatids. A gene
is a hereditary unit consisting of a sequence of DNA that occupies a specific location on a
chromosome and determines a particular characteristic in an organism. During mitosis, the
following stages occur:
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the chromosomes become visible
the nuclear membrane disappears
the chromosomes line up across the middle of the cell (the equator)
the chromatids of each chromosome separate and move to opposite ends of the cell
the chromatids become the new chromosomes of the daughter cells
a nuclear membrane forms around each set of chromosomes
the cytoplasm of the cell divides and a new cell wall forms between the two daughter
cells (these are the new cells resulting from mitosis).
The daughter cells each receive a complete set of chromosomes identical to those of the parent
cell. The daughter cells are genetically identical to the parent cell as they have exact copies of the
genes carrying the same information. There is no variation. This type of division occurs in
asexual reproduction in bacteria and in other unicellular organisms, such as Amoeba.
Diploid and Haploid
In each normal body cell of an organism, there is a fixed number of pairs of identical
chromosomes. This is known as the diploid number of chromosomes. For humans, the diploid
number is 46, consisting of 23 pairs. In peas, the diploid number is 14. The genes on each
member of a pair code for the same characteristics.
When mitosis takes place, separation of the chromatids ensures that the daughter cells have the
same diploid number of chromosomes and therefore the same genes as the parent cell.
When gamete formation occurs in meiosis, the way in which the chromosomes divide ensures
that each gamete has one of each pair of chromosomes. For example, human gametes will have
23 chromosomes and pea gametes will have 7. This is known as the haploid number. When
fertilisation occurs, the diploid number of chromosomes is restored, each gamete contributing
one of each pair to the zygote. One of each pair of chromosomes comes from the male parent and
the other from the female parent.
Meiosis
Meiosis is sometimes referred to as a 'reduction division' as it reduces the number of
chromosomes in the daughter cells. One major difference between mitosis and meiosis is that
meiosis involves two divisions of the nucleus. The first division separates the pairs of
chromosomes; the second division separates the chromatids.
Stages
During meiosis the following stages occur:
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the chromosomes become visible as
pairs of chromatids joined by a
centromere
chromosomes pair up (form
homologous pairs)
the nuclear membrane disappears
the homologous pairs of chromosomes
line up on the equator of the cell
the pairs separate, each moving to
opposite ends of the cell
a new nuclear membrane forms around
each set of chromosomes
the cytoplasm divides
the nuclear membrane of each daughter
cell disappears
the chromosomes line up on the equator
of each daughter cell
the chromatids of each chromosome
separate and move to opposite ends of
the cell
the chromatids become the new chromosomes of the daughter cells
a new nuclear membrane is formed around each set of chromosomes and the cytoplasm
divides.
As a result of meiosis, four daughter cells are formed.
Variation A gene is a section of a DNA molecule that codes for a particular characteristic, such as
tongue rolling in humans or flower colour in peas. Some people can roll their tongues, but others
cannot. If you inherit one form of the gene, you can roll your tongue, but if you inherit a different
form of that gene, you cannot. These different forms of the same gene are known as alleles. The
genes are arranged in a line along the chromosomes and are always found in the same position
on a specific chromosome. Each chromosome in a pair carries one allele for a particular specific
chromosome. Each chromosome in a pair carries one allele for a particular characteristic. These
alleles may both be the same or they may be different.
During the first division of meiosis, crossing-over may occur in which the chromatids of the
homologous chromosomes intertwine, and portions of these chromatids may be exchanged. This
means that alleles on one chromosome of S a pair may be exchanged for the alleles on the other
chromosome. When the I chromosomes separate, there could be new combinations of alleles on
each chromosome. This means that the gametes produced as a result of meiosis are not
genetically identical to the parent cell, and this in turn gives rise to variation in the offspring.
Variation only occurs as a result of sexual reproduction.
51. explain the nature and purpose of plant breeding
How characteristics are inherited
The characteristics of an organism are determined by the genes inherited from its parents. The
parents may have different alleles of some genes, and these may combine in different ways in the
offspring. This gives rise to variation.
To explain how characteristics are inherited, we can use the example of tongue rolling in
humans. A person who can roll their tongue may have inherited one allele for tongue rolling from
their mother and another from their father. But if the two alleles were different, that is one for
tongue rolling and one for non-rolling, the person would still be able to roll their tongue because
the tongue rolling allele is stronger: it is said to be dominant, and its effect will show. The allele
for non-rolling is said to be recessive and will not show if the dominant allele is present. If two
alleles for non-rolling were inherited, then the person would not be able to roll their tongue.
We can show this by using letters to represent the alleles. If the allele for tongue rolling is R and
the allele for non-rolling is r, a person who can roll their tongue could have the following
combinations of alleles: RR or Rr. A person unable to roll their tongue could only have the
combination rr.
When we write down the combinations of alleles for a particular characteristic, we refer to it as
the genotype as it describes the genetic make-up. So, RR, Rr and rr are all genotypes. Whether
the person is a tongue roller, or a non-roller is described as the phenotype: it is the appearance of
the characteristic as determined by the genes.
As we have seen, tongue rolling is a phenotype and there are two genotypes for this: RR and Rr.
In RR both alleles are the same and the person is said to be homozygous for the characteristic.
The other genotype (Rr) has two different alleles, and the person is said to be heterozygous. A
non-roller can only be homozygous (rr) with both recessive alleles. We can show how these
alleles are inherited in the following way: Let R represent the allele for tongue rolling. Let r
represent the allele for non-rolling.
Example A: If both parents are homozygous dominant, RR, then all the children will he tongue
rollers.
Example B: Let us see what happens if one parent (the mother) is RR and the other (the father) is
rr.
In this case, the father cannot roll his tongue, but the children will inherit R from their mother
and r from their father. So, all the children will have Rr as their genotype. As R is dominant, they
will all be tongue rollers.
Example C: If both parents are heterozygous, Rr, then the children could be rollers or non-rollers
depending on which combination of alleles they inherit. We can draw a table to show the
possibilities.
In both parents, half the gametes will carry the R allele and half the r allele, so the table shows
what the genotypes of the offspring are likely to be. There is a 1 in 4 chance of the offspring
being homozygous RR, a 2 in 4 chance of being heterozygous Rr, and a 1 in 4 chance of being
homozygous rr. This can be expressed as a 1:2:1 ratio.
When we consider the phenotypes, we can see that of the four possible combinations of alleles,
three will be rollers and there will be a non-roller. So, the ratio of phenotypes is 3:1.
Inheritance in plants
Characteristics in plants are inherited in exactly the same way as shown above in the tongue
rolling example. In pea plants, stem length is determined by a pair of alleles. Stems can be tall
(T) or dwarf (t). If a pure-breeding (homozygous) tall plant (TT) is crossed with a pure-breeding
dwarf plant (tt), then the offspring will all be tall but heterozygous. This is shown below.
If the offspring of this cross are interbred, there will be mixture of tall and dwarf plants produced
as shown below.
The ratio of genotypes is TT:2Tt:tt. The ratio of phenotypes is 3 tall:1 dwarf.
It is not possible to determine the genotype of the tall plants by looking at them. If a plant
breeder wanted a pure-breeding variety of pea plants, it would be necessary to carry out a special
cross to determine the genotypes of the tall peas. This type of cross is called a test cross or a back
cross. It involves growing the tall peas and crossing them with dwarf pea plants that have the
genotype tt. This type of cross is illustrated in Figure 11.6. Take a look at Figure 11.6. If the plant
breeder finds that some dwarf plants grow from seeds resulting from the back cross, then the
parents were heterozygous. But if all the seeds produce tall plants, then the parents were
homozygous.
Monohybrid inheritance
The cross shown in Figure 11.6 involves a single pair of alleles which code for a pair of
contrasting characteristics; it is called monohybrid inheritance. There are not many examples of
this type of inheritance in humans as most characteristics are controlled by a group of genes. For
example, height is controlled by many genes: if you arrange people in your class in a line from
shortest to tallest there might be a big difference between the extremes, but differences between
individuals would be small.
In crop plants, some examples of monohybrid inheritance include flower colour, seed shape and
pod colour in peas, bitter taste in cucumbers and hairiness of stems in tomatoes.
However, the appearance of a plant depends on environment as well as on the combinations of its
genes. If the growing conditions are not satisfactory and plants do not get sufficient nutrition,
they may not develop properly. For example, if a plant is deprived of light, it will lack
chlorophyll, be unable to make food by photosynthesis and therefore will not grow to its full
height.
Selection
The crop plants that we are familiar with have been selectively bred over many years to develop
favourable characteristics, such as larger yields or juicier fruits. Farmers have traditionally saved
seed from the best of their crop to sow the next year and in this way, over a long period, crops
have been improved. A good example of this type of artificial selection is shown by different
members of the cabbage family, the Brassicas (see Table 11.2). A wide range of vegetables have
been selectively bred over many years.
The staple diets of most countries involve members of the Graminae, or grass family. This family
includes rice, maize, wheat, oats, barley, rye, and millet. These cereal crops have been cultivated
for thousands of years and the varieties available today are the result of selection and
hybridisation. A hybrid is formed when two different varieties are crossed. The two varieties are
chosen for their desirable characteristics, which it is hoped will be combined in the offspring. For
example, if a variety of wheat with short stems is crossed with a variety resistant to drought, the
hybrid might have short stems (making it easier to harvest with less wasted as straw) and also be
able to survive dry conditions. It is not easy to predict the outcomes of such crosses and plant
breeders are continually developing new varieties. By carefully selecting varieties, plant breeders
are able to improve crop plants. The biggest benefit has been an increase in yields of grain in
cereal crops. This is of enormous importance in feeding the increasing world population. There is
now much interest in developing disease-resistance and drought tolerance in crop plants.
The major disadvantage to selective breeding is that it reduces variation so there are fewer
varieties of crop plants. If environmental circumstances change, such as a change in climate,
some of our present varieties might not thrive and it would be difficult to selectively breed new
ones. For this reason, it is important to keep seeds of older varieties so that these genetic
resources are available for breeding new varieties. Seeds are kept in seed banks, where
conditions are controlled to maintain their viability. Collections of plants in botanical gardens
and the preservation of old varieties of fruit trees in nurseries add to the reserves of genes which
could be used by plant breeders. These sources of genetic material are referred to as germplasm.
They are essential for the development of future varieties of crop plants.
52. explain the nature and purpose of biotechnology in plant improvement
Biotechnology involves using plant and animal cells and micro-organisms to produce useful
substances. People have used yeast to make beer, wine, and bread for thousands of years and we
also use fungi to make cheese and bacteria to make yoghurt.
Using bacteria to make disease-resistant plants
Recent knowledge of the structure of DNA has enabled scientists to alter the genes in the cells of
living organisms and to introduce characteristics from another living organism. This is known as
genetic engineering. A gene for a particular characteristic in one organism can be introduced into
another organism, called the host. For example, a gene for resistance to a certain disease can be
introduced into a host crop plant. When the crop plant is grown, it will not be damaged should
there be an outbreak of the disease.
Scientists can use bacteria to introduce new genetic material into the host cells. Bacteria are easy
to work with and it is possible to insert pieces of DNA carrying disease resistance into them.
When these bacteria enter the host plant, they cause it to produce cells which contain the new
DNA. These cells are then used to produce tiny plants which can be transplanted, and which will
grow into mature, disease-resistant plants. The tiny plants will all be genetically identical, and
they will all have the gene for disease-resistance. There are techniques other than using bacteria
that can be used to insert new genetic material into plants. There are also other examples of
genetic modification (GM) which are used to improve crops:
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Herbicide-resistance can be bred into crop plants: the crop is then sprayed with herbicide
to get rid of the weeds and only the weeds will be destroyed, not the crop (this has been
done with soya).
Resistance to insect pests: a gene is introduced into the crop plant which enables it to
make a lethal protein when attacked by the pest; the protein is toxic to the insect but not
to humans or other animals (this has been done with maize).
Virus-resistance: a gene has been introduced into rice plants which shows increased
resistance to the rice stripe virus.
Improved flavour and keeping qualities: genetic modification to tomatoes prevents the
softening of tomatoes as they ripen without altering the flavour and colour
Controversy about GM
Research into GM crops continues, and the possibilities are huge, with apparent benefits to
growers and for food production. However, not everyone believes that genetic modification is a
good thing. Some of the objections are:
•
•
•
•
it is a new technology and long-term effects are not known
the effects of eating GM products on human health cause particular concern
the modified genes from one species might get into other species
GM technology is an expensive process; often the technology has been developed by a
big corporation who charges much money for the GM seeds.
Genetically modified crops are not grown for public consumption until they have been
thoroughly tested. Any research involved in their production is controlled and the crops undergo
extensive field trials. In some countries, food prepared from GM crops has to be labelled so that
the public have a choice as to whether or not they buy it.
Other Uses for GM Technology
Genetic engineering is used in medicine to produce human hormones, such as: insulin and
growth hormone. It is also used to produce the enzyme (rennin) use in cheese making.
Traditionally, this enzyme was extracted from the stomachs of young calves, kids, or lambs, but
now it can be produced from genetically modified yeasts.
Crop Husbandry
53. describe the major cropping systems
A cropping system is a way of growing a crop or a range of crops. The major cropping systems
used by crop farmers include:
•
•
monoculture
multiple cropping or mixed cropping
•
•
•
•
•
•
•
intercropping
crop rotation
phased cropping
strip cropping
contour ploughing
mixed farming
cover cropping.
Sometimes a combination of cropping systems may be used, depending on the nature of the land,
the size of the farm and the type of crop production. For example, a mixed farm on hilly terrain
might use contour cropping, mixed cropping, and cover cropping.
Monoculture
Monoculture is the continuous cultivation and production of only one crop on a plot of land for
many years. A good example is the cultivation of sugar cane. This type of system can lead to a
build-up and rapid spread of pests and diseases which attack the crop, e.g., froghopper
infestations and smut disease in sugar cane. Monoculture is a risky business for the farmer
because he has invested a lot of effort into growing only one crop. Failure of the crop can result
in severe economic loss. However, some farmers have become specialised in the cultivation of a
specific crop, such as rice, pineapple, or pawpaw.
The farmer needs to invest in the machinery required for the cultivation, harvesting and
preparation for market of the chosen crop. For example, monoculture of sugar cane demands
investment in a sugar cane combine harvester.
Multiple cropping
Multiple cropping (also called mixed cropping) refers to the cultivation of two or more crops
simultaneously on the same plot of land. It is generally practised by peasant farmers. This type of
cropping system provides income on a regular and continuous basis for the farmer. The crops are
chosen carefully so that:
•
•
•
•
some crops have a shorter growing period and others a longer growing period
crops grow to different heights
some are deep-rooted and others shallower-rooted
the water and nutrient requirements of the crops are not the same.
The benefits of this type of cropping include:
•
•
•
•
•
•
an improvement in, or maintenance of, soil fertility, irrigation, and drainage
easier management of pest control and a reduction in pest infestations
easier management of fertiliser application and weed control
control of soil erosion as different crops provides different forms of vegetative cover to
the soil
a smaller risk of total crop failure
a variety of crops produced
•
a reduction in pest infestations.
Crops suitable for this type of cropping are soyabean and pigeon pea, root crops and cereals.
Intercropping
Intercropping is the cultivation of a short-term crop, such as lettuce, between the plants of a
medium-term crop, such as sweet pepper. It enables the farmer to earn some quick income from
the sale of the lettuce crop while the main crop of sweet peppers develops. It requires careful
selection in terms of compatibility so that one crop is not smothered by the rapid growth of the
other. This type of cropping system helps the farmer to use the space between plants of the main
crop more efficiently. Soil fertility is maintained, and soil nitrogen may even increase,
particularly if one crop is a legume such as beans. The vegetative cover provided by two crops
helps to control soil erosion on sloping ground.
Crop rotation
Crop rotation is the cultivation of selected crops in succession (one after the other) on the same
plot of land. For example, a sequence of tomato, bean (a legume), lettuce and beetroot help to
maintain soil fertility because the legume crop adds nitrogen to the soil. In addition, the inclusion
of deep-rooted and shallow-rooted crops enables soil nutrients to be used from different levels in
the soil. The other benefit is that the build-up of pests and diseases in the soil is prevented (pests
and diseases are usually specific to one type of crop).
Phased Cropping
Phased cropping is a system of continuous cropping and harvesting. A plot of land is divided into
four sections. The planting dates are sequenced so that there is continuous cropping and
harvesting of the produce, section by section. In this way, a farmer can maintain a regular supply
of produce to consumers and receive a steady income over time. This type of cropping prevents
an oversupply, or glut, of a commodity which would have the effect of lowering the price on the
market.
Strip cropping and contour cropping
Both these cropping systems can be used for the cultivation of crops on sloping land. Strip
cropping refers to planting different crops in strips of varying width on flat, undulating, or
sloping land. It is normally used as a soil conservation measure on slopes. It has similar
advantages to multiple cropping. Contour cropping is another method of conserving soil on
sloping land. The land is ploughed along the contours and then crops are planted. In this way,
soil erosion through heavy rainfall is prevented.
Mixed farming
Mixed farms may be small, medium, or large and produce both crops and livestock. A variety of
cropping systems may be used depending on the nature of the land and size of the farm. Many
organic farms (see page 35) are mixed farms.
Cover cropping
Cover cropping is used to improve soil fertility and to prevent soil erosion. It involves planting a
crop that grows rapidly and provides cover on bare soil. The cover crop is usually planted after
the main crop has been harvested and can be ploughed into the soil before the land is re-planted.
The cover crop, often referred to as 'green manure', provides a cover of vegetation for the soil
and adds organic matter when ploughed in. If a legume, such as cowpea or vetch, is planted, then
the nitrogen content of the soil is increased. Cover crops may be sown between the rows of other
crops, particularly between rows of fruit trees in an orchard.
54. discuss the benefits of the cultural practices associated with crop production
55. describe the cultural practices associated with crop production
Many activities (see Table 12.1) are necessary to ensure the optimum growth of a crop so that its
production is profitable. These activities improve or maintain soil fertility, so that the growth of
the crop is maximised. Many of the techniques used are described in Chapter 8.
56. explain the effects of weeds on crop production
A weed is any plant that is growing in the wrong place — or where it is not wanted. This
definition means that any plant can be a weed: the seeds of the previous year's crop can produce
'weeds' if they germinate in the ground where a different crop has been planted. Weeds are in
competition with crop plants for space in which to grow and for light, water, and nutrients. If
weed growth in a crop is heavy, then crop plants are deprived of their requirements and the yield
and quality of the produce will suffer. Weeds can also contaminate the crop produce with their
seeds and fruits. Some weed species act as hosts for pests (such as aphids) and disease-causing
organisms. If weeds in a crop become infected, then disease-causing organisms can infect the
crop plant and cause damage. Some weeds (e.g., redhead) are poisonous to livestock, especially
cattle and horses which may stray on to the fields.
Why are weeds so successful?
Weeds are successful in competing with crop plants because:
• they germinate and grow very rapidly; if conditions are good, they will grow into large plants
producing many seeds; if conditions are less favourable, they can produce plants which will be
smaller but still produce seeds
•
•
they produce large numbers of seeds under favourable conditions
they can often reproduce vegetatively as well as producing seeds; those weeds that
produce underground stems or rhizomes can be spread by cultural practices such as
hoeing and tillage
•
•
•
the seeds are easily dispersed, often over a wide area; many weed seeds are dispersed by
wind and can be carried long distances
the seeds may remain viable (capable of germination) in the soil for a long period; in
some species of weeds, germination occurs when conditions are favourable (some weeds
will germinate on exposure to light, so they will germinate when the soil is disturbed by
tillage)
they grow very rapidly in the seedling stages; if they germinate before the crop seeds,
they can grow much faster than the crop and smother the crop seedlings.
Most of the major weed species belong to just a few plant families: the grasses (Gramineae), the
sedges (Cyperaceae) and the composites, such as railway daisy and red thistle (Compositae). In
the Caribbean, annual and perennial grasses, vines, and woody plants can be problem weeds.
Possible benefits of weeds
In general, weeds are harmful, but their rapid germination and growth on bare soil provides a
cover of vegetation which can help to prevent soil erosion due to heavy rainfall.
In some cropping systems, fields can be left without a crop (fallow) for a growing season and
then weeds are ploughed in before the next crop is planted. The ploughed-in weeds add organic
matter to the soil.
In addition, weeds growing around fields attract beneficial insects, such as bees, and other
insects which prey on some crop pests.
57. identify different methods of weed control
It is important to control weeds within a crop to ensure a good yield and good quality of produce.
Methods of weed control include:
•
•
•
•
cultural control — adequate preparation of the land and cultural practices such as hand
weeding and hoeing
chemical control — the use of weedkillers (herbicides)
biological control — using other organisms to control weed growth
integrated control — combining two or more methods which are suited to a particular
crop.
Cultural methods
There are several measures that a farmer can take to minimise the spread of weeds.
•
•
Buying good quality seed from an authorised supplier will ensure that weeds are not
sown with the crop. Cheap seed may be contaminated with weed seeds or other crop
seeds. If there are broken or empty seeds, then the density of crop plants will be affected
and there will be more room for weeds to grow.
Cleaning tools and equipment after use will prevent weed seeds from spreading to other
crops.
•
•
•
•
•
•
•
Crop rotation helps in weed control. Some weeds are associated with certain crops and
planting different crops in rotation can control a particular weed. For example, a parasitic
weed called Striga affects maize, sorghum, and cowpea; this can be controlled by
planting a different crop in successive years.
Mulching can control weeds by depriving them of light for photosynthesis and also
preventing the germination of weed seeds.
When land is cleared, the vegetation is sometimes burned. This has the benefit of getting
rid of annual weeds but does not destroy the underground parts of perennial weeds. It also
destroys useful soil organisms. Soil may be sterilised by burning before crop seeds are
sown.
Ploughing will turn the soil over and bury any weeds, but it may also b ring buried weed
seeds to the surface where they will germinate and grow before the crop. Ploughing
prepares land for the crop, but it cannot be used to control weeds in a crop that has started
to grow.
Hand weeding is where weeds are pulled out by hand or by using a hoe or a cutlass. This
is an effective method, but it is labour-intensive and time-consuming. Use of a hoe or a
cutlass may damage onions, potatoes, and cassava, and it is not an effective method
against perennial weeds. Care needs to be taken when removing weeds with herbaceous
jointed stems that root easily; even a small piece left in the soil can grow. When hand
weeding, it is important to distinguish weed seedlings from the crop seedlings so that
there is minimum loss of crop seedlings.
Mowing is used to control weeds in pastures, lawns, and orchards. It needs to be done
when weeds are mature but before they have produced flowers and seeds.
Flooding is a method of weed control used in rice fields. It will get rid of weeds that
cannot tolerate being covered in water.
Herbicides
Herbicides are chemicals used to kill weeds. They may be selective herbicides, killing some
plants and not others, or non-selective herbicides, killing all plants that they come into contact
with. The use of herbicides is a very efficient method of controlling weeds and saves hours of
manual labour. The type of herbicide used depends on:
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•
•
•
the state of the land: if land is fallow it will need to be treated differently from land that
has been recently used for growing crops
the type of crop: the herbicide should not kill the crop so a selective weedkiller that kills
broad-leaved weeds should only be used on a cereal crop, such as maize, or sugar cane
the type of weed: some selective herbicides kill broad-leaved weeds and others kill grass
weeds
the stage of growth of the crop: some herbicides are applied before the shoots of the crop
come above the ground (pre-emergent herbicides), some after the shoots have emerged
(post-emergent herbicides), and some when the crop is mature and just before harvesting
(post-maturity herbicides).
Non-selective herbicides
Some herbicides may be applied to soil to kill all the weeds present before the crop is planted.
These are usually non-selective, and the land is ploughed or harrowed after the application.
Glyphosate and Paraquat are herbicides used in this way and they are effective at controlling
annual weeds. Paraquat is a contact herbicide; when it comes into contact with the leaves it
interferes with photosynthesis by destroying the cell membranes. Glyphosate is a systemic
herbicide and works within the plant. Both these herbicides have no lasting effects in the soil:
Glyphosate is broken down to harmless compounds by soil micro-organisms within a few days
and is not very toxic to mammals. Paraquat is classed as 'moderately toxic' by the World Health
Organisation (WHO).
Selective herbicides
Selective herbicides are used once the crop has been planted. A systemic herbicide is used, which
is taken up from the soil by weed seedlings and carried within the weed to the growing regions
where it produces its effect. Sometimes weed seedlings absorb the herbicide through the leaves.
Atrazine, Alachlor and Metolachlor are systemic herbicides which kill grass weeds and are also
effective against some broad-leaved weeds.
Precautions
When spraying crops with herbicides, protective clothing should be worn, and safety precautions
taken to avoid spillage and contamination of other areas. All the instructions provided for correct
application should be followed. If spraying is on a large scale, then weather conditions need to be
considered. It is wasteful to spray if there is a high wind or heavy rainfall. Research into the
development of new herbicides is taking place all the time, so it is wise to check with suppliers
and extension officers to keep up to date.
Biological methods
Biological methods of weed control involve the use of other living organisms to control the
weeds. Biological methods include:
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•
•
•
cover cropping: the use of a legume crop, such as mung beans or cowpeas, to provide
vegetative cover has been described on page 117; it prevents growth of weeds and also
adds nitrogen to the soil when ploughed in; the disadvantage is that the farmer has to
purchase the legume seeds
planting density: the density of the crop will affect the growth of weeds; the higher the
density of the crop, the less room for the weeds; the density should be adjusted so that
crop plants can develop fully but little room is left for weeds; if the crop density is too
high then plants will be small, and yield reduced
choice of crops: low-growing crops, such as sweet potatoes, and broad-leaved crops that
spread quickly, such as melons and zucchini, cover the soil surface and prevent the
growth of weeds
grazing: sheep and goats can be used to clear weeds from pastures
•
introducing a pest of the weed species: this involves using an insect pest or a disease that
affects the weed; it needs to be carefully controlled and is not suitable on a small scale.
For example, adults of Longitarsus jacobaeae, the Ragwort Flea Beetle, attack ragwort
plants and cause extensive damage. The beetle larvae intensify this attack by feeding on
the roots of this poisonous weed.
Integrated control
Different methods of weed control may be used at different stages of crop growth. Integrated
control means using a combination of control methods. The use of non-selective herbicides and
ploughing may be the best treatment during preparation of the land before the crop is sown. Once
the crop is at the seedling stage, hand weeding can be effective on small plots and avoids the use
of chemical sprays. The choice of herbicides depends on the type of cropping system in use,
particularly as herbicides effective for one vegetable crop are not effective against another.
58. identify pests and the damages caused by pests
A variety of pests (mainly insects) cause damage to crops. Other animal pests include:
•
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rodents, such as rats, which damage standing crops and stored crops; rats are serious pests
of sugar cane, gnawing through stems and causing the plants to fall over; bacteria may
get into damaged stems
birds, which feed on fruit crops, such as grapes, mangoes, papaya and banana, and
damage young seedlings of vegetable crops
mites, which belong to the same major group as spiders, and feed on the leaves of crop
plants.
Insect pests
Insects damage plants by:
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the adults or larvae feeding on the crop
the adults laying eggs inside flowers, fruit, or stems; when they hatch, the larvae often
feed on leaves and bark, e.g., treehoppers on apple trees
acting as carriers (vectors) of viral diseases (aphids act as vectors by transmitting plant
viral diseases).
Insects can be divided into two feeding groups:
•
•
the biters and chewers
the piercers and suckers.
The biters and chewers, such as beetles, grasshoppers, crickets, ants, bees, and wasps, eat their
way through plants leaving holes. The larvae of butterflies and moths (caterpillars) and flies
(maggots) are also chewers. By destroying leaves, these insects reduce the amount of food that
the plant can make by photosynthesis, resulting in poor growth and decreased yield. Often, a
severe infestation can destroy the whole crop.
Sucking insects, such as aphids, have piercing mouthparts which suck sap from inside the soft
tissues of the plants, resulting in reduced growth. The adult stages of flies and moths are also
sucking insects. Table 12.2 shows some common insect pests of food crops.
59. identify the cause, symptoms, and mode of transmission of major crop diseases
Crop diseases can be caused by a number of different organisms. These organisms are called
pathogenic organisms (disease-causing organisms) and enter plants through damaged tissues, the
stomata on leaves or by insects feeding on plants. Once inside the plant, a pathogen causes an
infection. It deprives the plant of nutrients and water and produces visible signs (symptoms),
such as yellowing of the leaves and wilting.
Table 12.3 summarises some diseases caused by these organisms, their symptoms and mode of
transmission.
Types of pathogens
The following groups of organisms can cause diseases in crop plants:
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•
•
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fungi: organisms that do not possess chlorophyll; consist of a network of fine threads
which spread throughout the plant absorbing nutrients; usually produce masses of spores
(see Figure 12.6)
bacteria: microscopic, single-celled organisms; obtain their nutrients from the host plant;
multiply rapidly inside the host (see Figure 12.7)
viruses: very small structures; consist of nucleic acid surrounded by a protein coat; can
only reproduce inside the cells of the host; cannot survive for long outside another living
organism
mycoplasmas: tiny organisms which are smaller than bacteria
protozoa: small, single-celled micro-organisms; differ from bacteria in that they have a
true nucleus surrounded by a nuclear membrane (eukaryotic), while bacteria do not
(prokaryotic)
nematodes: very small (about 1 mm in length), non-segmented worms which are present
in large numbers in soil.
60. recommend the appropriate methods of pests and disease management
Plants can be protected from pests and diseases in a number of ways involving cultural
techniques, chemical and biological control, and integrated pest management (IPM).
Cultural techniques
Cultural techniques include: • removal of pests by hand: this is time-consuming but effective for
caterpillars on cabbages; it avoids the use of chemicals which could contaminate produce; but it
is difficult to carry out for most pests • disinfection and sterilisation of soil: this technique kills
weed seeds, insect eggs and larvae and fungal spores; banana corms can be disinfected with hot
water • destruction of any infected plants or produce: citrus trees infected with a virus are burned
• crop rotation: reduces the spread of insect pests that infect specific crops • planting diseaseresistant varieties of crop plants: prevents or reduces infection; disease-resistance can be selected
for and many varieties of crop plants are available (see Chapter 11).
Chemical control
A pesticide is a chemical substance used to control pests. It is poisonous (toxic) to the pest but
does not harm the crop. Pesticides are classified according to the type of pest they control and
include herbicides (kill weeds), insecticides (kill insects), fungicides (kill fungi) and nematicides
(kill nematodes). Some naturally occurring insecticides, such as Pyrethrum and Nicotine, have
been in use for hundreds of years, but many newer artificial chemicals are now in use. Pesticides
can also be classified according to the way in which they work.
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Contact pesticides are sprayed on to the crop and they coat the plants. Contact fungicides
treat fungal diseases and are absorbed by the fungal pathogens. Contact insecticides get
into the bodies of insect pests through their respiratory systems. These pesticides do not
persist for long on the crop plants; they may get washed off by rain so have to be reapplied to control the pest. They are relatively cheap and effective. Examples:
Organochlorines, Pyrethroids, Carbamates.
Systemic pesticides are absorbed through the leaves and roots of crop plants and are
translocated (carried) around the plant. The cell sap becomes toxic to the pest which is
•
destroyed as it feeds on the crop. The advantage of the systemic pesticides is that they
remain in the plant for a long time and can protect the crop from possible infestations
before they occur. Examples: Organophosphates, some Carbamates.
Residual pesticides are sprayed on the land before a crop is planted. They kill weed
seedlings, fungal spores, insect eggs and larvae. They have a relatively long-lasting
effect, although heavy rainfall will cause leaching. They may be used as part of the land
preparation operations undertaken before sowing or planting. Most residual pesticides
have their effect through direct contact with the pest.
Biological control
Biological control (see page 193) relies on the natural predators or parasites of the pest organism.
For example, ladybirds and hover flies feed on aphids, birds eat caterpillars and fish eat insect
larvae. Nowadays the term is usually reserved for the deliberate introduction of one species (a
predator) to control another species (the prey). The pest is eaten by the predator.
Biological control is mainly used against insect pests. Other examples of this predator-prey
relationship include:
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control of rabbits in arable crops and pasture by introducing the myxomatosis virus
introduction of the Argentinean moth borer to control the growth of prickly pear on
grazing land
control of mala ria by the introduction of fish to eat the mosquito larvae
control of stem borer in sugar cane by introducing wasps from India, Apanteles flavipes
and Paratheresia, and the Cuban Fly, Lexophaga.
The most successful use of biological control has been in the protection of greenhouse crops,
where conditions are controlled, and the pest insects and their predators are contained in an
enclosed area. The aim is to control the pest but not eliminate it totally as this deprives the
predator of food. Numbers of pest insects and predators will fluctuate but the level of infestation
is kept low. This type of control has been used to protect cucumbers, tomatoes, and other salad
crops. Whitefly, a pest of cucumber, is readily controlled by the tiny wasp Encarsia formosa.
Natural predators of insects are often found on vegetation bordering field plots; such predators
can be encouraged by leaving the edges of fields uncultivated. Sometimes strips of uncultivated
land are left within field plots. These are referred to as 'beetle banks' and they provide a habitat
for insect predators. These measures often mean that less pesticide is required.
Integrated pest management (IPM)
Integrated pest management aims to control pests by using a combination of methods to keep
pest populations at low levels rather than totally eliminating them. IPM uses cultural and
biological control methods, instead of relying solely on chemicals.
If pesticides are used, they should be chosen for their short-term toxicity (so that they break
down to harmless substances in a short time). Also, they should not be used over a long period as
the insect pests could develop resistance to them. Development of pesticides is expensive, so
relying just on pesticides will cost the farmer more money than following cultural and biological
control methods.
61. evaluate the effects of indiscriminate use of chemicals in the environment
There is widespread use of chemicals in the form of pesticides, weedkillers, and artificial
fertilisers. Using chemicals brings obvious advantages to the farmer and the consumer, but there
are also disadvantages. Many scientists are concerned that agricultural chemicals are damaging
our environment.
Advantages of using agricultural chemicals
The advantages include:
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•
•
the effects of application may be seen relatively quickly: pests and weeds can be
destroyed before they cause much damage to the crop improved crop yields: crops benefit
from the removal of weeds and pests and will grow better; farmers make more profit;
there is a better supply of good quality produce for the consumer.
pest and weed control take less time: manual and cultural methods are more timeconsuming and labour-intensive; the farmer who uses chemicals has more time for other
operations
a longer storage life for food: better quality produce will be produced, which will last
longer.
Problems with agricultural chemicals
For some time, there has been concern about agricultural chemicals that get into the
environment. Chemicals applied to the soil or sprayed on to crops can be reached by rainwater
into rivers and eventually into the oceans. Excessive use of chemicals can cause pollution and
affect the plant and animal life of both freshwater waterways and the oceans. Chemicals may
build up in organisms (such as shellfish) — these chemicals are subsequently eaten by other
animals higher up the food chain. The chemicals get concentrated in these animals and
sometimes kill them.
Eutrophication
Artificial fertilisers, such as NPK fertilisers, get washed from farmlands into rivers. The increase
in nitrates and phosphates in a river increases the growth of algae. This creates an 'algal bloom' in
the surface layers of the water, blocking sunlight from other aquatic plants. When the algae die,
they are broken down by bacteria which use up oxygen in the water. Because artificial fertilisers
increase numbers of algae and bacteria, the water becomes deoxygenated (lacking in oxygen). As
a result, other aerobic organisms in the water, such as insects, insect larvae and fish, will
suffocate and die. This increase in nitrates and phosphates in the water is called eutrophication.
Eutrophication can also occur if there are sewage spills or a run-off from farm manure, as these
contain nitrates and phosphates.
Pesticides
Pesticides can also get into waterways, either as drift from crop spraying or from being washed
off plants and down through the soil by rain. The toxicity of pesticides and their effect on crop
plants has to be thoroughly investigated before the pesticide can be marketed. Sometimes
chemicals produced when the pesticides break down may affect other organisms in the
environment. DDT is an example of how a pesticide can affect other organisms. This is a contact
insecticide that had been used successfully for years to kill a range of insect pests, including
mosquitoes. It had low toxicity to humans, so it was safe to apply to food crops, but it took a
long time to break down in the soil. In the 1960s, DDT and compounds derived from DDT were
found in a range of organisms, including humans. Unfortunately, DDT had entered the food
chain. DDT had seeped from soil into rivers and been absorbed by small organisms, which were
eaten by larger organisms, eventually getting into the bodies of the top carnivores. It was found
that DDT accumulated in the organisms at the top of the food chain. For example, some birds of
prey started to produce eggs with very thin shells. The eggs failed to hatch and there was a
decline in numbers of these birds. The use of DDT was banned worldwide in the early 1970s.
Since the problems with DDT, there have been more investigations into the long-term effects of
pesticides. Research has concentrated on the development of chemicals which break down more
readily. In addition, pesticides are being developed to target specific pests.
Pesticide labelling
Pesticide labelling is now enforced by law. Labels must contain the following information:
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•
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•
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•
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•
•
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the product name or the trade name
the type of pests it will control
a list of the active ingredients and their amounts; the official chemical names must be
included and often the common names are given as well
the percentage of the inert (inactive) ingredients; inert ingredients do not need to be listed
by name
the quantity of the product in the container
the name and address of the manufacturer
a registration reference to indicate that the product has been tested for use
an indication of the toxicity
precautionary statements about keeping the product away from children, emergency and
first aid treatment
reference to physical, chemical, and environmental hazards
directions for use
storage instructions.
The directions for use should be followed carefully as they will indicate:
•
•
•
where and when the pesticide can be used
how much to use
how it needs to be mixed
•
•
safety equipment to be worn and safety precautions to be followed when applying the
pesticide
how long after application the crop can be harvested.
62. Cultivate a fruit, root, leaf, and flower vegetable crop
Keeping Records
Individual crops have different requirements and need therefore different treatments.
When growing different crops, it is useful to keep records of the following:
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•
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•
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•
•
•
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the crop name and variety chosen
how the land was prepared
the type of material planted: seeds, seedlings, cuttings, tubers, rhizomes, suckers, bulbs
date of planting
fertiliser treatment: type, quantity, and rate of application
methods of weed control used
pests and disease control if needed: type of pest or disease; treatment given
cultural practices: irrigation, drainage, moulding, mulching, pruning, staking,
intercropping
harvesting: date of harvest; yield
post-harvest handling: trimming, washing, grading, weighing, packaging, storage
marketing: pricing, labelling, selling
economic value: calculate total inputs and work out profit or loss.
Such records are essential to a farmer and help him to calculate income (see Chapter 7). They are
also helpful as a reference for future enterprises and help the farmer to decide what crops and
varieties to grow, what will thrive on his land, and what treatments are most successful. On a
smaller scale, it is interesting to compare the yield from different varieties and the effectiveness
of different fertilisers and pesticides on crops grown in vegetable plots or containers.
Accessing information
The farmer needs to be able to access useful information about crop cultivation procedures.
Below are some examples of information relating to cultivating four different crops.
63. explain the importance of plant quarantine
Alien pests and alien diseases are pests and diseases which do not occur naturally in a country.
Their introduction into a country can cause much damage. With an increase in world trade, much
agricultural produce is now exported and imported. Crops are transported by air and can reach
their destination in hours. In most countries, strict regulations ensure that only the highest quality
pest-free produce is exported and that all imported goods are inspected.
The introduction of alien pest species, such as weeds and insects, could cause havoc to
agricultural production in that country. There may be no natural predators for the pests, so they
could spread rapidly and damage crops. Imported plant material can carry viruses and it would
be dangerous if such material were to be used for plant breeding.
In most countries, there are restrictions on the importation of plant material. It can only be
imported with permission and from accredited suppliers. All imported material is inspected at the
point of entry. Even the baggage of passengers entering the country is inspected and any
unauthorised plant material may be confiscated.
In the USA, regulations stop the movement of certain crops from one state to another to control
the spread of pests. Quarantine centres are established by the Ministry of Agriculture at airports
and ports and employ qualified personnel to carry out inspections. Each territory in the
Caribbean has its own regulations and operates its own quarantine centres.
Harvesting and Postharvest Practices
64. define postharvest technology
Post-harvest technology refers to processes developed to handle, store and market produce after
it has been harvested. An understanding of the way in which crops ripen, the changes that take
place after harvest, and correct storage conditions can prevent wastage. This will increase profits
for the farmer. Poor handling of crops after harvest causes a loss of produce that has taken time,
labour, and materials to cultivate. The economic consequences can be serious, particularly if
produce has to be transported any distance. There is less wastage if produce is grown and
consumed locally, as there is less time for deterioration. Post-harvest technology needs to be
applied if fresh produce is grown at a distance from where it is consumed.
When to take special care
Care needs to be taken during:
•
•
•
•
•
harvesting: so that crops are not damaged by bruising or cutting
cleaning, grading, and packaging: careful handling will prevent bruising
storage before being taken to market: cool conditions will slow ripening and prevent
dehydration
transportation: proper packaging will prevent damage; refrigeration is needed for
perishable produce
long-term storage: cereals and other produce stored for long periods need to be stored
under the correct conditions to prevent damage by pests.
65. identify the stages of maturity at the time of harvest
Signs of maturity The useful and edible parts of crop plants are harvested at the desirable stage of
maturity, and this varies according to the type of crop. Maturity is related to age of the crop and
may be associated with:
•
•
•
changes in colour
the drying up of stems and leaves
characteristics linked with marketability, processing, and use.
Some crops are harvested at the fully developed or mature stage. This is recognised by the
farmer, who inspects the crop looking for specific signs.
Signs of maturity include:
•
•
tomato: fully mature stage; browning in the region of the calyx
yam, eddo: fully mature stage; die-back or drying of the aerial stem and leaves
•
•
•
•
•
•
•
•
avocado, guava: fully mature stage; changes in skin colouration, from dark green to
yellowish green
banana (for export): 75% full (mature) or 75% fully developed stage
bodi beans, ochro, loofah: snap stage
cucumber, spinach, eggplant (melongene): succulent (juicy and not too fibrous) stage
coconut (water nut): soft/medium jelly stage
melon, pawpaw, pumpkin, citrus, hot pepper: ripe or ripening stage
paddy (rice), corn (maize), coconuts: dry stage
egg plant, gourd: soft, plump stage.
The timing of harvesting
The timing of harvesting depends on several factors as listed below.
•
•
•
•
The age of the crop: this can be calculated using the date of planting and serves as a
harvesting guide for the farmer. The period from planting to harvest for some crops can
be relatively short (lettuce — 6 weeks, cabbage — 3-4 months), but for others the wait is
much longer (bananas — 9 months, cassava — 6 to 12 months depending on the
cultivar).
The type of crop: some crops, such as lettuce, dry-corn, and rice, are harvested all at
once, making way for a new crop to be planted. Tomatoes, bodi beans, ochro and hot
peppers produce fruit continually for a period, even after a first harvest. These crops need
to be harvested regularly as new produce reaches the desirable stage of maturity.
Time between harvestings: the time between successive harvestings varies according to
the crop. Some examples are: ochro — 2 to 3 days, bodi beans —4 to 5 days, spinach —
6 to 7 days and karaile — 5 to 7 days.
Weather conditions: cool weather is favourable for harvesting lettuce, Pak choi, cabbage,
cucumbers, sweet peppers, and beans. Sunny weather reduces the moisture content in
crop produce and ripens grains, making it easier for harvesting rice, corn, and sugar cane.
Dry weather makes harvesting operations using machinery easier as the soil is dry.
66. recommend the appropriate harvesting method for crops
Harvesting methods used vary according to the crop and the cropping system under which it was
grown. All methods should be carefully carried out to ensure that produce (plant parts) being
harvested is not damaged. Manual harvesting is used for cocoa, coffee, bananas, and yams.
Mechanical harvesting, by mean of combine harvesters, is used for rice, corn, and sugar cane.
Manual harvesting methods
These methods include hand-picking, uprooting, the use of a knife or a cutlass, or digging out
with a fork. They are used for crops grown in small plots, using multiple cropping or
intercropping systems and where fields are not accessible to machinery. Manual methods (see
Table 13.1) include:
•
•
•
•
•
•
•
•
nipping-off with the thumb and index finger: bodi beans, cucumbers, karaile, hot peppers,
string beans
uprooting and trimming with cutlass and knife: cassava, radish, carrot
digging out with fork, spade or luchette: yam, sweet potato, ginger, cassava
cutting off, with pedicel (fruit stalk) and calyx (sepals) attached, using secateurs: Portugal
orange, mandarin, sorrel, ochro, melongene, sweet pepper
cutting stalks with a sickle and threshing the grains: rice (paddy)
cutting stalks with a cutlass: sugar cane
hand picking: tomato, mango, guava, citrus, maize
picking with a goulet: cocoa, breadfruit, breadnut • using a fruit-picker: avocado.
Mechanical harvesting methods
Machines for mechanical harvesting speed up the process of gathering in a crop, saving time and
manual labour. The simplest types of machines can be attached to a tractor, such as the sweet
potato harvester. This is designed to dig the tubers and lift them from the soil on to a conveyer
belt.
Combine harvesters are used for grain crops. They cut the crop, thresh, and winnow the grain.
The grain is gathered into trailers and is transported away for storage. Sugar cane can also be
harvested by specially designed combine machines. Mechanical harvesting methods are common
on large farms where fields are easily accessible. It saves time and labour, although the cost of
machinery is a drawback.
There are problems associated with using heavy machinery in poor weather conditions or where
the terrain is hilly. Harvesting methods have to be adapted to the crop, the nature of the farm
(small, medium or large, on hilly terrain or flat), and weather conditions.
67. describe the harvest and postharvest practices for heliconia, orchid, ginger lily and
anthurium
Ornamental crops need special harvesting techniques and post-harvest treatment to ensure they
reach the market in prime condition. Chapter 21 has more information on ornamentals.
Anthurium (Anthurium genus)
Depending on their size at planting, suckers produce flowers in 3 to 6 months. Hybrids may
produce 12 flowers per year. Flowers are harvested when the spathe (the hood-like leaf
surrounding the spadix) is fully opened, the flower stalk is firm up to the bloom and the spadix
(candle) is firm and rough with prominent seed buds. Using secateurs, blooms are cut with a
stalk length 40 to 80 cm and placed upright in baskets.
Post-harvest handling: flowers are stored in a cool area, graded according to size, colour and
injury; then they are packed in boxes.
Heliconia (Heliconia genus)
Heliconia plants produce blooms 9 months after planting. They are cut, using secateurs, and
placed in baskets. The flower stalks may be of varying lengths.
Post-harvest handling: blooms are taken to a cool area, where they are graded and then packed in
boxes.
Ginger lily (Hedychium genus)
Using secateurs, blooms are cut off together with 2 leaves on the flower stalk. The blooms are
placed in a basket with flowers protruding upwards.
Post-harvest handling: Cut flowers are placed with their basal ends in buckets, which have been
half-filled with clean water, in a cool place. Blooms are later graded and placed in boxes for
export; or into small bundles of 6 and covered with clear polythene for the local market.
Orchid (Orchis genus)
Orchid blooms are cut using secateurs. Sprays are cut with as long a stem as possible, including
some buds and flowers. Blooms are placed in a basket and transported quickly to the storage
area.
Post-harvest handling: Cut flowers may be placed into special orchid tubes filled with water to
support the stems. They are packed in boxes and stored in a cool place.
68. explain postharvest operations from the farm to the table
The quality of produce can only be maintained and not improved by post-harvest operations and
most fresh. produce is highly perishable (this means that it will decay quickly). Harvested
produce generates heat through respiration and loses moisture rapidly, causing wilting and
shrivelling. Fruits such as bananas release ethylene gas which causes ripening so the presence of
a few ripe bananas can bring about ripening in other fruits. Rough handling bruises the produce,
and it can decay, releasing unpleasant odours. Post-harvest management:
•
•
•
•
extends the shelf-life of produce
allows more time for transportation, storage, processing, marketing and use of produce
allows the produce to be sold to markets further away
brings satisfaction to both consumers and producers.
Post-harvest and harvesting techniques
The following techniques can help in producing high quality produce.
•
•
•
•
•
•
•
Harvesting early in the morning or late in the evening and when the weather is cool or
cloudy.
Pre-cooling the produce. This should take place as soon as possible; care should be taken
to keep produce out of the sun by covering it.
Cold water sprays can keep produce fresh.
Careful packing to avoid bruising and damage; avoid rough handling during packing,
loading and unloading.
The use of large baskets, trays and crates for packing.
Avoidance of movement during transportation by securing containers firmly (movement
could damage and bruise the produce).
Storage of produce at the recommended temperatures.
The consumer wants good quality, fresh produce that is clean and will not deteriorate quickly.
Urban and peri-urban farmers can supply such produce directly to the markets or sell their
produce at roadside stalls. Produce may be trimmed to remove brown, dirty or wilted outer
leaves, washed to remove soil, and graded before being packaged by the farmer into perforated
polythene bags. Polythene bags help to retain moisture and improve presentation for the
customer.
Farmers without immediate access to a market will have to sell produce to a wholesaler or a
retailer. The trimming, washing and grading is usually carried out by the farmer, but the
wholesaler or retailer may package the produce. Fresh produce on sale in shops and
supermarkets has a limited shelf life, so it is stored in a cool place before being displayed. Often
it is packaged to retain freshness and to avoid too much handling which could affect the quality.
Consumers may prefer their guavas, sapodillas and mangoes to be of uniform size, so similar
sized fruits are often packaged together.
Processing and Utilization
69. outline the reasons for processing crops
Crops are processed to:
•
•
•
preserve them
convert them into another food product
extract a product from them.
Preservation
Preservation prevents the growth of micro-organisms, such as bacteria and fungi, which cause
decay and spoilage. It also prevents food from deteriorating through oxidation or through
enzyme activity within the cells of the food. Preservation may change the texture, taste and
appearance of the food, but microbial decay is prevented or reduced. Short-term preservation
keeps food fit for consumption for days or weeks, long-term works for months or years. Microorganisms can be killed by heat, or their growth is slowed down by low temperatures or lack of
water (dehydration). Enzyme activity in cells is also affected by temperature and the presence of
water. Oxidation can be prevented by the exclusion of air.
Conversion into another food product
Food processing often involves turning foods into other food products.
•
•
•
•
Cereal grains are processed into flour for baking, breakfast cereals and feed for animals.
Grains are also processed during the production of beer.
Grapes are processed to make wine. Apples can be converted into cider.
Fresh fruit and vegetables are used in the preparation of a wide variety of products and
cooked dishes. For example, tomatoes may be processed into tomato juice, tomato puree,
tomato sauce, soups and cooking sauces.
Extraction of a product
Sometimes a food product has to be extracted from the food source.
•
•
Sugar cane has to undergo processing before the product can be used. The stems contain
a sugary sap which must be extracted before it can be processed into sugar.
Some plants, such as olives, sunflowers and rape, are grown for their oil. The fruits or
seeds are harvested, and the oil is extracted by pressing.
70. identify the various types of processing techniques
Food processing techniques include:
•
•
•
•
•
the use of heat
refrigeration
freezing
drying
fermentation.
Heat
Short-term preservation of food can be achieved by blanching, which involves plunging the food
into hot water for a few seconds to a few minutes. Micro-organisms on the surface may be
destroyed and enzymes within the tissues of the food will be inactivated. Blanching is used to
treat fruit and vegetables before they are processed.
Further processing may involve freezing, drying or canning, or to preserve their colour.
Blanching does not significantly alter the texture or taste of the food. Cooking can preserve food
in the short term. The food is heated to a high temperature for a short period. The temperature
within the food reaches 70°C, which is high enough to destroy most micro-organisms. Cooking
alters the texture and colour of fruit and vegetables, making them softer. Cooked food, if not
eaten straightaway, can be cooled, refrigerated and kept for a few days; or they can be frozen and
kept for longer.
Pasteurisation
Heat is also used in pasteurisation. Pasteurisation is used to treat milk, but also in the short-term
preservation of fruit juices and other foods. In the process, food is heated to 72°C for 15 seconds,
cooled and then packed into sterile containers or cartons and sealed. The cartons are refrigerated
before use. Once a carton has been opened and exposed to the air, the contents need to be
consumed within a few days. Pasteurisation destroys pathogenic micro-organisms but does not
alter taste or the nutritional content.
UHT treatment
UHT (Ultra High Temperature) treatment involves heating food to a much higher temperature,
132°C, for a few seconds, placing it in sterile cartons and sealing. With this treatment, the
product can be kept without refrigeration for several months. However, once opened, the
contents should be used within days. Foods preserved in this way include milk, fruit and
vegetable juices.
Canning and jam-making
Long-term preservation of foods is achieved by canning. The food is first cleaned, sorted and
graded for quality. It is then blanched, which softens it and makes it easier to pack into the cans
(some foods may be cooked). The food is packed into cans and then liquid is added. If vegetables
are being canned, the liquid is usually brine; but fruit juice or sugar syrup is used for fruits. Lids
are placed on the cans; they are sealed and then the cans are heated to a high temperature in
steam under pressure to sterilise the contents. The length of the heating period depends on the
type of food being canned, the size of the container and the pH of the contents. Sugary foods and
those with a low pH need less time than other foods. After being held at the correct temperature
for the required time, the cans are immediately cooled in cold water. Many fruits and vegetables
are preserved in this way and can be stored for years. The texture of the food is changed: it is
softer.
Heat is also used in jam-making, in which fruits are cleaned, sorted and boiled in syrup made of
water and sugar. Heating destroys micro-organisms and the syrup removes water from the fruit.
The jam is poured into jars, whilst still hot, and sealed to prevent entry of micro-organisms. Fruit
preserved in this way can be kept for months.
Refrigeration
Many vegetable crops are grown to provide fresh produce. The crops are harvested when they
reach maturity or when they ripen, packed carefully and transported to wholesalers, retailers,
stores and markets to be sold within a short time. Freshness can be prolonged by storing produce
at cool temperatures or by packaging to prevent loss of water by evaporation. The activity of
micro-organisms is slowed at low temperatures, so storing food in a refrigerator kept at 1°C to
4°C will keep it fresh for several days. Where the climate is warm, it is usual to keep opened
cartons of food refrigerated to prevent the growth of bacteria. Cooked food should be covered
and cooled before refrigeration.
Freezing
The freezing process causes water in the tissues of the food to be turned to ice. The low
temperatures needed for the process reduce the activity of micro-organisms and may destroy
some. They also stop chemical reactions inside cells as the enzymes are inactivated. The
formation of ice draws out water from the tissues and they become dehydrated. This process can
preserve many fruits and vegetables, although the texture of soft fruits, such as strawberries, is
altered. The freezing technique is used commercially and can also be used for fresh produce in
the home. The fruit and vegetables to be frozen are cleaned, graded and vegetables are usually
blanched. In addition to destroying micro-organisms on the outside of the produce, blanching
displaces any trapped air. The colour of some vegetables, such as peas, beans and leafy
vegetables, may become brighter. Freezing is carried out as quickly as possible, so that large ice
crystals do not form, and the cells of the food are not damaged when the tissue thaws. The
temperature inside the food may need to reach -5°C or lower before ice crystals are formed. The
frozen produce is then packaged, labelled and stored at -20°C in a freezer for months. Freezing
does not destroy all micro-organisms, so most frozen food should be cooked thoroughly soon
after thawing.
Drying
Drying or dehydration means removing all water from foods to prevent decay. The activity of
micro-organisms stops when the water level inside cells is low. The micro-organisms are not
killed, and their activity is resumed when the food is re-hydrated. Drying can be carried out by
leaving fruit, vegetables and herbs in the sun. This is a traditional method used to dry plums,
sorrel, green mango (cut into strips) and grapes, herbs and peppers. The fruits are spread on trays
and turned occasionally to promote rapid and even drying. If conditions are not favourable for
drying food outdoors, it can be achieved by forcing heated air over the food.
Freeze-drying
Many foods are preserved by freeze-drying, in which food is first frozen and then ice is
converted to water vapour by sublimation. To carry out this process, the food is frozen and then
placed in a vacuum. The ice crystals are converted to water vapour without becoming liquid. The
vapour re-condenses to ice on metal plates provided for the purpose. The quality of freeze-dried
food is good and, although the texture may be changed, the taste is not altered.
This technique works well with fruit and vegetables. The vacuum is broken by adding nitrogen
gas, which is chemically inert, and the products can then be sealed in airtight packages and do
not need to be refrigerated. Freeze-dried foods are convenient as they do not take up much space
and only require water for rehydration before they can be consumed. They are used in military
rations and stores for camping trips, where it would be difficult to carry fresh food.
Freeze-drying can be achieved using a domestic freezer and using a metal mesh rack or a cakecooling tray. Very thin slices of apple, for example, are spread on the tray and placed in the
freezer. If left for a week, depending on the thickness of the slices and the temperature of the
freezer, they should be dry and can be reconstituted by pouring boiling water on to them. If not
completely dry, they will thaw out and turn black.
Fermentation
Fermentation in food processing involves the use of micro-organisms, such as yeasts and
bacteria, to produce alcohol or organic acids from carbohydrates. Fermentation is involved in the
production of:
•
•
•
•
sauerkraut from cabbage
soya sauce from soya beans
wine from grapes and other fruits
beer from barley.
Sauerkraut
In sauerkraut manufacture, naturally occurring bacteria on the surface of cabbage ferment sugars
under anaerobic conditions forming lactic acid. Cabbages are washed in clean water, shredded
and mixed with salt. The material is packed into a large container, a weight placed on the top,
and the container is covered closely. The salt draws water from the tissues, so the cabbage shreds
become immersed in brine. Bacterial activity uses up available oxygen and the conditions
become anaerobic, favouring bacteria which bring about the formation of lactic acid.
Fermentation is complete when the pH reaches 3.5. The container is kept between 21°C and
24°C. If the temperature is lower, then fermentation is slow, and the desired pH is not achieved.
Fermentation at higher temperatures may cause the growth of other, undesirable micro-organisms
that would cause spoilage. In this fermentation process, the micro-organisms are respiring
anaerobically, using sugars in the cabbage and producing lactic acid as their waste product.
Soya sauce
The soya bean (Glycine max) is a leguminous plant grown throughout the world. It is high in
protein, oil and vitamins. It is poisonous if eaten raw, so must be cooked or processed first. The
production of soya sauce consists of the following stages: • soya beans are soaked in water,
boiled, drained and added to starchy material, such as crushed wheat or flour • the mixture is
spread out on trays and a starter culture of bacteria and moulds is added • fermentation takes
place for a week at 28°C to 30°C; the moulds release enzymes which break down complex
carbohydrates in the mixture to simple sugars and amino acids • brine (17-22% solution of
sodium chloride) is added and the mixture is transferred to a large container • a second
fermentation, this time anaerobic, takes place and lactic acid is produced, lowering the pH; the
temperature is kept between 25°C and 33°C and the process can take a few months • the mature
sauce, now a dark brown liquid, is filtered off and pasteurised before being bottled. Variations in
flavour and colour of the sauce can be made by altering the fermentation conditions or microorganisms present in the starter culture. The first fermentation is aerobic and releases sugars and
amino acids used in the second fermentation, which is anaerobic.
Winemaking
In winemaking, yeasts (Saccharomyces cerevisiae and other species) ferment sugars under
anaerobic conditions to produce alcohol. In this type of fermentation, sugars in the fruit (mainly
glucose and fructose) are respired anaerobically by yeast to produce carbon dioxide and alcohol.
Wine is usually made from grapes, but other fruits, vegetables and grains may be used.
The process involves the following stages:
•
•
•
the fruit is crushed, and juice pressed out; skins and pips are removed if white wine is
being made; red wine is made from black grapes and some skins are left in the juice to
give colour to the wine
the juice may be pasteurised to destroy micro-organisms on the outside of fruit: many
fruits have natural yeasts on their skins which may not produce the desired fermentation
the juice is placed in a large container and yeast added; initially the conditions are aerobic
because there is oxygen dissolved in the juice and the contents of the container are mixed
to encourage the growth of the yeast
•
•
•
after a few days, all dissolved oxygen is used up; the mixing is stopped, the container
covered and as conditions become anaerobic, ethanol is produced, and carbon dioxide is
given off
after the first stage of fermentation, clear wine is drawn off from the residue (a process
called racking) and left to continue fermenting; this process may be repeated several
times until fermentation is complete
the wine may be left in oak barrels to mature or bottled straightaway; red wine is usually
left to mature and develop its flavour before being drunk.
If wine is made on a smaller scale, glass fermenting bottles fitted with air locks are used. It is
then easy to follow the process of fermentation and know when the wine requires racking. The
temperature at which fermentation takes place should be between 10°C and 20°C for white
wines, but 24°C to 27°C for red wines. Different yeasts produce different concentrations of
alcohol in the wine, as well as characteristic flavours.
Making beer
In the brewing of beer, barley is allowed to germinate so that starch in the grains is converted to
sugars. The germination is suddenly stopped by drying and roasting the grains, which are then
ground up and mashed with water. The sweet liquor extracted from the mash contains sugars.
Yeast is added and anaerobic fermentation produces alcohol and carbon dioxide. Hops (the
flower clusters of Humulus lupulus) are added to give the characteristic flavour and to counter
the sweetness of the remaining sugars.
Cocoa
Cocoa undergoes a fermentation process during its production (see Figure 14.4). Cocoa pods are
harvested from the trees and opened with a hammer or a machete. The husk and inner membrane
of each pod is discarded. The pulp and seeds are removed, piled in heaps, covered with banana
leaves or jute bags and allowed to 'sweat'. This is a fermentation process. During sweating, the
thick pulp ferments and becomes liquid. This takes 3-9 days and removes the bitter taste of the
cocoa. During fermentation, sugars in the beans are converted to acids (lactic and acetic acid)
and a high temperature is generated (about 52°C). Enzymes inside the beans are activated and
form compounds which produce the chocolate flavour when the beans are roasted. After
fermentation, the beans are dried before being processed locally or exported.
71. state how the processed product is utilized
Section C: Animal Production
Morphology and Physiology
72. relate the structure of the digestive system of a bird to its functions
Nutrition
Farm animals can only derive value from their food following ingestion, digestion and
absorption of nutrients into the bloodstream. The nutrients are assimilated (taken into) into the
body of the animal and either used or stored. Nutrition is essential for:
•
•
•
•
maintaining a supply of energy
growth
body maintenance and repair
reproduction.
Stages of digestion
The digestive systems of farm animals vary in structure, but basically, they all consist of a tube,
called the digestive tract or alimentary canal, extending from mouth to anus. All types of
digestive systems carry out similar functions, which are:
•
•
•
•
ingestion: intake of food
digestion: break down of food
absorption: uptake of nutrients into the bloodstream
egestion: elimination of undigested residues (faeces).
Processes involved in digestion
Digestion is the process by which ingested food is broken down into simpler compounds by the
digestive system. These compounds are then absorbed through the mucous membrane lining of
the alimentary canal into the bloodstream. The breakdown of food in digestion can involve
physical, chemical and microbial processes:
•
•
•
Physical processes: mastication (chewing) by the teeth and muscular contractions of the
digestive tract (peristalsis) break up the food and move it through the alimentary canal
Chemical processes: enzymes in the digestive juices secreted along the alimentary canal
and by its associated organs bring about the breakdown of food; complex food molecules
are broken down into simpler, soluble substances.
Microbial processes: enzymes secreted by micro-organisms (bacteria and protozoa) in the
stomachs of ruminants break down cellulose; micro-organisms in the colon and caecum
of non-ruminants secrete enzymes that break down limited amounts of cellulose.
Parts of the alimentary canal
The main parts of the alimentary canal, or digestive system, are:
•
•
the mouth
the oesophagus, or gullet (including the crop in poultry)
•
•
•
•
the stomach: simple (monogastric, e.g., pig) or complex (ruminant, e.g., sheep); in birds
the stomach is made up of the proventriculus and the gizzard
the small intestine: duodenum and ileum
the large intestine: caecum, colon, rectum and anus
the accessory, or associated, organs: salivary glands, liver and pancreas.
Poultry
In poultry (see Figure 15.1), the crop and proventriculus form part of the oesophagus. The
gizzard is a tough, muscular organ which contains grit, or small' stones. Powerful muscles in the
gizzard contract and relax, helping to grind food. There is no grinding of food in the mouth as
there are no teeth. The digestive juices and their enzymes are similar in nature and function to
those secreted by a pig.
73. identify the parts of the digestive system of ruminant and non-ruminant animals
Ruminants
Ruminants are animals (sheep, goats and cattle) that eat grass and other vegetation and chew the
cud (ruminate). The cud is undigested vegetation which has been swallowed and then
regurgitated back into the mouth for thorough chewing. When it is re-swallowed, the cud passes
into the digestive system. The stomach in ruminants is complex. At the base of the oesophagus
there are four compartments. Three of these, the rumen, reticulum and omasum, referred to as
forestomach; and the fourth, the abomasum, is the true stomach. In the rumen, bacteria and
protozoa digest the cellulose in fibrous food. Ruminants crop the vegetation, mixed with saliva
and swallowed. It passes down the oesophagus into the rumen where it is stored. When the
animal has finished feeding, small quantities of food (each called a bolus) are regurgitated for
further chewing.
Non-ruminants
Non-ruminants, such as pigs, rabbits and poultry, have simple, or monogastric, stomachs. There
is no digestion of cellulose or highly fibrous foods in the upper part of the digestive system, but
some occurs in the large intestine and caecum due to the activities of bacteria. Some fibrous food
material is needed in the diets of non-ruminant farm animals to encourage peristalsis (the
movement of food through the gut) and to prevent constipation.
74. explain the functions of the parts of the digestive system of ruminant and non-ruminant
animals
The ruminant digestive system differs from the non-ruminant system in the complexity of the
forestomach and the stomach. Tables 15.2 and 15.3 summarise the digestive systems of a pig and
a cow.
75. describe the process of digestion in ruminant and non- ruminant animals
Digestion in the pig (non-ruminant)
Food is chewed in the mouth and mixed with saliva, which contains water, mucus and the
enzyme salivary amylase. The water and mucus moisten food, making it easier to swallow. The
salivary amylase begins the process of breaking down starch to sugars.
The stomach
Food is swallowed and enters the oesophagus (gullet). From here it is transported into the
stomach by a series of wave-like muscular contractions, known as peristalsis. Once in the
stomach, it is mixed with gastric juice and churned by muscular contractions. The gastric juice,
secreted by glands in the wall of the stomach, contains mucus, hydrochloric acid and the enzyme
pepsin, which starts the breakdown of proteins to amino acids.
The small intestine
The food, now called chyme, enters the first part of the small intestine (the duodenum), where it
is mixed with bile from the gall bladder and pancreatic juice from the pancreas. Bile does not
contain any enzymes, but it emulsifies (breaks down) large globules of fats into smaller droplets,
making it easier for the enzyme lipase (from the pancreatic juice) to digest the fats. Pancreatic
juice is alkaline and neutralises the very acidic chyme, creating the optimum pH conditions (pH
7-8) for the action of enzymes in the small intestine. Pancreatic juice contains the following
enzymes:
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pancreatic amylase which continues the breakdown of starch to sugars
lipase which brings about the breakdown of fats to fatty acids and glycerol
trypsin which continues the breakdown of proteins to amino acids.
Food passes into the second part of the small intestine, the ileum. Intestinal juice acts upon the
chyme, continuing the digestion of the carbohydrates, fats and proteins. The carbohydrates are
broken down to simple sugars, the proteins to amino acids, and the fats to fatty acids and
glycerol. The food is now in a fluid, watery state referred to as chyle. The wall of the ileum has
many finger-like projections called villi (singular: villus), which increase the surface area
available for the absorption of the digested food. Each villus has a thin wall and a dense network
of capillaries. Sugars, amino acids, fatty acids, glycerol, vitamins and minerals pass into the
capillaries; from here they are transported to the liver for processing and assimilation into the
body cells.
The large intestine
After absorption has taken place, the food residues (water, undigested material, cellulose,
digestive secretions and bacteria) move into the colon, or large intestine. Bacterial action in the
caecum and the colon results in the synthesis of some vitamins (vitamin B) and some digestion
of cellulose. Much water is reabsorbed into the blood from the colon and the rectum, minimising
water loss from the body. The residues, now called faeces, pass into the rectum, where more
water is reabsorbed. The faeces are stored in the rectum until they are egested through the anus.
Digestion in ruminants
In the adult ruminant, food is taken into the mouth and roughly chewed, mixed with saliva and
swallowed. It moves by peristalsis down the oesophagus and into the rumen. Saliva lubricates the
food, making it easier to swallow and helping to neutralise acids formed in the rumen by
microbial activity. The saliva maintains the pH of the rumen at the optimum level (pH 5.5 to 6.5).
In the rumen, food is continually churned by rhythmic contractions of its walls. Through antiperistaltic action, larger pieces of food form boluses. These are regurgitated in succession back
up the oesophagus into the mouth. Here, each bolus is chewed 40-50 times before being
swallowed again. The chewing breaks up the food physically and provides a larger surface area
for the action of enzymes from bacteria and protozoa. On re-entering the rumen, food is exposed
to enzymes produced by micro-organisms. This brings about chemical digestion. The
contractions of the rumen and reticulum help to separate large particles of food for regurgitation
to the mouth. Finer particles are channelled to the omasum, where they are stored temporarily.
The omasum crushes the food particles, squeezing water and liquid food into the abomasum or
true stomach. In the abomasum, gastric juice is secreted and the course of digestion from this
point on is similar to that in non-ruminants. In suckling ruminants, such as calves, kids and
lambs, the rumen and reticulum are not fully developed and only enlarge as young animals begin
to consume solid food. The milk they take in is channelled directly to the omasum and
abomasum for digestion.
76. explain digestion in rabbits
The rabbit is an herbivore with a simple stomach and not a ruminant. The rabbit is a pseudoruminant: it does not chew the cud or have a rumen, but it does depend on bacterial digestion of
cellulose for much of its nutrition. Rabbits are fed on:
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herbage: water grass, kudzu, sweet potato vines, railway daisy, rabbit meat (herb), leaves
of lettuce, cabbage, cauliflower, bodi and Pak choi
root crops: carrot, sweet potato, radish and cassava
concentrates: rabbit ration or substitutes such as broiler starter, chick starter, pullet
grower and pig grower
kitchen scraps: bread soaked in milk, discarded leaves of cabbage, Pak choi, lettuce and
cauliflower, vegetable peelings.
Fresh herbage is collected, cleaned and spread thinly on an herbage rack to wilt before feeding.
Wilting reduces the moisture content and helps to prevent soft, watery faeces or 'scouring'.
The rabbit's diet contains cellulose which is not broken down until food reaches the caecum.
Undigested food passes from the small intestine into the caecum and appendix where there are
cellulose-digesting bacteria, which break down cellulose to organic adds. Faecal pellets
(droppings) egested during the night are produced by the caecum and are soft. These pellets are
eaten by the rabbit, supplying vitamins and amino acids as well as the products of the bacterial
digestion of cellulose. Hard, dry faecal pellets are produced during the daytime and consist of
undigested food wastes. The alimentary canal has a very large caecum in which microbial action
takes place.
The habit of eating the soft droppings is called coprophagy and enables the animal to derive the
greatest amount of nutrition from the ingested and re-ingested material.
77. relate the structure of the parts of an egg to its function
An egg contains the female gamete, or ovum, of a bird. A hen's egg is ovoid in shape, 5 cm to 6
cm in length, with one end more pointed than the other. The outer, protective shell is made of
calcium carbonate (98%) together with some magnesium and phosphate. It is hard and may vary
from white to brown, depending on the breed and age of the hen. It has many pores which allow
gaseous exchange for the fertilised egg.
The parts of a hen's egg
The egg has:
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two shell membranes which protect the inner parts; the shell is built on the outer shell
membrane; the inner shell membrane surrounds the albumen
albumen (egg white): made up of proteins, minerals, some carbohydrate and water;
provides some food and a source of water; protects against bacterial infection; protects
the yolk from mechanical injury; albumen is of two types, thick and thin; the thin
albumen is found just below the shell and surrounding the yolk
chalazae: coils of twisted fibres made from albumen; hold the yolk in place
the yolk: contains fats (phospholipids); provides food for the developing embryo if egg is
fertilised: yellow colour is due to pigments
a germinal disc, or blastoderm; seen as a white disc on the uppermost surface of the yolk;
if the egg was fertilised this will develop into the embryo
the vitelline membrane: surrounds and supports the yolk • the air space: this is situated at
the blunt end; it is important for gas exchange; the air space gets bigger the longer the
egg is stored as water is lost from the albumen.
To some extent, the colour of the yolk is influenced by the diet of the hen. Grass and maize
contain yellow pigments; if these are included in the poultry feed, the yolks have a dark yellow
colour.
Nutrition
78. identify the sources of carbohydrates, proteins, fats, minerals and vitamins
Nutrients are the substances in food that animals need in order to stay healthy. They are essential
for the growth, energy, body maintenance and reproduction of farm animals. Farm animals get
their nutrients from the following sources:
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plants: grasses, forage crops, legumes
plant products: corn, soyabean, oat bran, rice husks
animal products: bone meal, milk, fish meal. The groups of nutrients required by farm
animals are carbohydrates, fats, proteins, vitamins, minerals and water.
Carbohydrates
Carbohydrates are energy-producing foods and contain carbon, hydrogen and oxygen, e.g., C6H
12O6 (glucose). Carbohydrates can be of three types:
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monosaccharides: simple sugars, e.g., glucose, fructose
disaccharides: consist of two monosaccharide units, e.g., maltose, sucrose, lactose
polysaccharides: composed of many monosaccharide units, e.g., starch, cellulose.
Carbohydrates in the diet of farm animals provide energy for:
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metabolic activity
physical work
the production of meat, milk and eggs.
Sources of carbohydrates are plants, such as pasture grasses, and plant products such as root
crops, fruits, seeds and grains.
Proteins
Proteins are organic compounds made up of amino acids. They are essential for the formation of
all living cells. They contain carbon, hydrogen, oxygen and nitrogen, together with sulphur and
phosphorus. Proteins in the diets of farm animals are essential for:
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building new cells and tissues, including muscles
producing milk, eggs, wool, hair and feathers
body maintenance: the repair and replacement of tissues
producing enzymes and hormones.
Sources of proteins include plants, such as pasture legumes, cowpea and soyabean, and animal
products, such as fish meal, bone meal and blood meal.
Fats (lipids)
Fats are made up of fatty acids and glycerol. They contain carbon, hydrogen and oxygen, and are
similar to carbohydrates in that they are energy-producing foods. Fats contain more energy per
unit weight than any other food constituent; about 2.5 times that of a similar weight of
carbohydrate. Fats in the diet of farm animals are used to:
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supply energy
store energy.
In farm animals, surplus energy from carbohydrates is converted to fat. This is stored under the
skin, within the muscle tissues and in the abdominal cavity.
Sources of fats include coconut meal and linseed meal after the oil has been extracted. The lipid
content of forage rarely exceeds 4% but it is rich in unsaturated fatty adds.
Vitamins
Vitamins are organic compounds required in the diet in small quantities for healthy growth and
development. They are grouped into:
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fat-soluble vitamins: vitamins A, D, E and K
water-soluble vitamins: vitamins B and C.
Their major role in the diet is to promote normal health, growth and development. A lack of
vitamins may result in diseases or abnormalities, such as:
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retarded growth
poor reproduction
skin ailments
haemorrhage (over-bleeding)
diarrhoea
night blindness
rough coat
muscular problems.
Sources of vitamins include green pasture grasses, cereal grains and sunshine (vitamin D is
manufactured in the body in the presence of sunshine).
Minerals
Minerals are essential in the diet of farm animals as they have a similar role to vitamins in
promoting healthy growth and development (see Table 16.1). There are 16 essential mineral
elements which can be divided into two main groups:
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major or macro-elements needed in fairly large amounts: calcium, phosphorus,
potassium, sodium, chlorine, sulphur and magnesium
micro or trace elements needed in very small amounts: iron, zinc, iodine, copper,
manganese, cobalt, selenium, fluorine and molybdenum.
Farm animals derive minerals from:
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green pasture grasses and forages
legumes, including pasture legumes
cereal grains, such as corn and rice
mineral licks (saltlicks/blocks)
blood meal, fish meal, bone meal.
Local materials for livestock feeds
Feed for farm animals can be de rived locally. Several crop plants (cereals, grasses and legumes)
are specifically grown for animal feed. Crops that do not reach marketable quality (sweet potato,
yam, carrot and cassava, for example) and the trimmings from leafy crops such as cabbages are
also used to feed livestock. By-products from the processing of food are good sources of animal
feedstuffs. These include:
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bagasse and molasses from the processing of sugar cane: used for cattle feed
fish meal from fish: a high protein supplement used in aquaculture
rice bran, rice husk and rice-middling: used for rabbits and horses in the form of a bran
mash
wheat-middling, wheat bran, oat bran, soya bean meal from the milling and processing of
cereals: used for rabbits and horses; soya bean meal is used as a protein supplement for
dairy cows
citrus pulp and citrus meal: provide a concentrated source of nutrients for dairy and beef
cattle and sheep; rich in calcium
coconut meal: protein supplement for livestock
cocoa pod meal from the processing of cocoa beans: used in livestock and poultry feed
brewer's grain and hops from the brewing industry: good source of proteins and watersoluble vitamins; useful for both ruminants and non- ruminants
urea from fertiliser manufacture: urea/bagasse mix is used to feed beef cattle
waste food (swill) from restaurants and hotels: used to feed pigs,
79. explain ‘balanced ration’
The term ration refers to the type, quality and quantity of food that is fed to a particular farm
animal or group of animals. A ration can be divided into two parts:
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the maintenance requirement: for body repairs and metabolic processes
the production requirement: for the production of meat, milk or eggs.
The following factors need to be considered:
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the age of the animals
their physical condition
the stage of growth they have reached
the essential food nutrients they need.
Ideally a ration should supply all the essential food substances in their correct proportions.
Types of rations
There are three types of rations: maintenance, production and balanced. The maintenance ration
is a diet which satisfies the energy (carbohydrates and fats), and protein needs of the animal. It
provides for body repairs (maintenance) and metabolic processes, without any gain or loss in its
stored energy reserves or body weight.
The production ration is the extra food, added to the maintenance requirement, which is used by
the farm animal for productive purposes. Meat, milk, eggs, hair, wool and offspring (calves,
lambs, kids) result from the production ration.
The balanced ration consists of all the essential nutrients in amounts needed to satisfy both
maintenance and production requirements of the animal.
A balanced ration:
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supplies all the essential food constituents
has the correct proportion of energy to protein, as well as vitamins and minerals
is usually more palatable and satisfies the animal's appetite.
A lack of any essential food constituent may damage the health and production of the animal.
But overfeeding can also be a problem. Feeding too much food will waste the farmer's money.
Nutrients will just be lost in the faeces and health problems may develop in the farm animal.
80. select appropriate rations for each stage of growth of broilers and layers
Feedstuffs
Livestock feeds, known as feedstuffs, provide nutrients for energy, growth and development,
maintenance, production and reproduction. Feedstuffs can be classified into the following
groups:
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forages: green pasture grasses, legumes, mulberry and neem; the farm animals are
allowed to graze, or the forages are cut and fed to them in stalls; also includes the thick,
fleshy, juicy stems, roots, fruits and leaves of certain crops, such as sweet potato, cassava
and banana
fodder: dried feedstuffs, such as hay, straw and chaff, are used when forage is
unavailable; can also include green chopped feedstuffs, such as corn stalks, elephant
grass and kudzu
silage: pasture grasses, legumes and other crops conserved and stored in silos
concentrates: commercially produced in feed mills using local and imported foodstuffs;
designed to suit the maintenance and production needs of different farm animals; they can
be mixed, mashed, ground, granular or pelleted; they may be high protein, low protein,
high fibre, low fibre, high carbohydrate, rich in essential vitamins and minerals, low
percentage fat or low moisture content.
The nutritive value of feedstuffs varies. Laboratory analysis provides information on the total
amounts, in percentages, of crude (potential) nutrients contained in commercial feeds. These are
expressed as Total Digestive Nutrients (TDN) or Net Energy Values (NEV). Farm animals,
however, can only use the nutrients from foods which have been digested. This means that some
nutrients are always lost in the undigested material which passes out in the faeces.
Broilers and layers
When choosing rations for poultry you need to consider: • the stage of growth or development:
chicks, adult broilers, pullets or laying hens • the name of the ration: starter, grower, finisher,
layer or egg ration • the cost: high protein feeds (e.g., starter) are usually more expensive than
low protein feeds, such as finisher.
Poultry are fed starter ration from day-old chicks until they are 6 weeks old. Hens reared for egg
production are then fed on grower ration until they are 15 weeks old. At 15 weeks, they are fed
on laying ration, or egg ration, until they are culled. Poultry reared for production (broilers) are
fed on finisher ration from 7 to 9 weeks old.
81. calculate Feed Conversion Ratio (FCR)
All farm animals, especially those reared for meat (broilers, piglets and calves), convert feed
consumed into body mass. The feed conversion ratio (FCR) is the number of units of feed (kg)
which the animal requires to produce a one unit (kg) increase in its body weight. It is expressed,
for example, as 3.0:1 or 2.5:1, that is 3 kg of feed or 2.5 kg of feed needed to produce a 1 kg
increase in body weight.
This ratio is associated with efficiency on the part of the farm animal and economics in terms of
the cost of feed to the farmer. However, the efficiency of conversion can vary among animals of
the same breed and in the same litter. In a group of calves, some may have an FCR of 3.5:1 and
others an FCR of 3.0:1. The calves with the lower FCR are more efficient converters than those
with the higher FCR.
A young animal converts feed more efficiently than an older one. For example, a piglet may have
an FCR of 1.5:1; but as it grows and increases in size, the FCR increases. This is shown in Table
16.2.
82. explain the importance of FCR
Feed is a major expense in rearing livestock, especially meat-producing animals. Farmers are
well aware of this fact! An understanding of FCR can be helpful in:
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selection of classes and breeds of animals which have a low feed conversion ratio
identification of particular animals which are efficient feed converters: these can be kept
for replacement stock and breeding purposes
raising early maturing farm animals, thereby controlling expenditure on feed
marketing batches of mature farm animals promptly before the feed conversion ratio
increases this avoids spending more on feed at a time when the increase in body weight is
slowing down.
83. describe systems of grazing
Grazing animals eat grasses or the leaves of other plants. Examples of grazing animals are cattle,
goats and sheep. Grazing systems (see Figure 16.3) focus on:
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the effective use of pasture grass or legumes (the sward)
maintenance of high-quality forage for a long period
the balanced regrowth of grass and legumes after grazing
a high level of production from ruminant livestock
Zero grazing (soilage or soiling)
Zero grazing refers to the cutting, chopping and feeding of forage crops to ruminants housed in
pens or stalls. The animals feed on grass without having to graze, hence the term zero grazing.
Examples of the soilage grass/legume mixtures used in this system include:
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elephant grass/Centrosema
guinea grass/kudzu
Guatemala grassl Stylosanthes
pangola grass/Centrosema.
Rotational grazing
In rotational grazing, the pasture area is sub-divided into six or eight paddocks. Each is
systematically grazed in sequence; the ruminants being moved from one paddock to another. The
stocking rate is usually high, (20 to 25 cows per hectare). Each paddock is grazed for 3 to 7 days,
depending on stocking rate and herbage growth. After that time, the paddock is rested, and the
animals are moved on to another paddock. The system continues until the last paddock has been
grazed and the cycle is then repeated. When paddocks are not being grazed, they undergo pasture
management.
Strip grazing
Strip grazing is a variation of the rotational system: a single paddock is progressively grazed,
strip by strip, using movable electric fences to restrict the animals. The fences can be moved
forwards once or twice daily, offering the animals a strip of fresh pasture for grazing.
Continuous grazing
In continuous grazing, animals are allowed to graze on the same pasture area for a very long
period. This system is normally only practised on expansive range lands where fencing is absent
and probably impractical. The stocking rate is usually low.
Deferred grazing
In deferred grazing, certain paddocks of pasture grass/legumes are withheld for later use. In
tropical countries, it is the practice of conserving 'standing hay'. The forage that is withheld
usually matures, loses its succulence, palatability and some nutritive value; but it is important as
a maintenance ration, especially in the dry season. Leafier grasses and legumes, such as guinea
grass/kudzu and giant star grass/Centrosema are most suitable for this type of grazing.
Pasture management
Farmers who rear ruminants recognise the importance of establishing good pastures and
managing them effectively. A well-managed pasture will:
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provide much palatable, digestible and nutritious food for ruminants
guarantee a continuous supply of fresh food
•
promote forage conservation for periods of slow growth, drought and scarcity • reduce
expenditure on commercial feeds.
Management tips
On well-established pasture, the farmer can maintain the pasture by carrying out these activities:
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adopting systems of grazing to achieve the most efficient use of the forage produced
avoiding over-grazing or close grazing: regrowth and root development of grasses and
legumes is slowed; death of forage plants could result in bare patches and soil erosion
avoiding under-grazing: this leads to a decrease in the nutritive value of the pasture
(protein content decreases and the fibre content increases) and this promotes patches of
tall, dense grass
tine-harrowing the pasture after rotational grazing and after rain: matted stolons are
broken up, dung from grazing animals is spread around, and growth of unsuitable grasses
is prevented
mowing or brush cutting pasture after rotational grazing: coarse growth is removed,
tillering of the grasses is promoted and weeds are controlled
applying fertilisers at regular intervals: nutrients for plant growth are supplied and the
rapid re-growth of the forage is promoted
clearing clogged drains and watercourses
mending pasture fences
pruning or re-planting shade trees.
84. state the advantages and disadvantages of different grazing systems
Zero grazing
The advantages of zero grazing are that:
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efficient use is made of the forage
there is a high level of animal production
herbage is not trampled or fouled by the animals
forage can be harvested at its most succulent, palatable and nutritious stage.
The disadvantages include:
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the need for special machinery and equipment for harvesting, transporting and chopping
the high cost of setting up and maintaining housing for the animals, the machinery and
equipment
increased labour costs, bedding material for the animals and manure disposal
restriction on numbers of animals reared: it is only suitable for small herds of ruminants.
Rotational grazing
The advantages of this system are that:
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it overcomes the problems associated with over-grazing and under-grazing
it makes efficient use of the forage
it promotes a high level of production
animals with high nutritional needs, such as dairy cows (high producers), can be given
'first bite' of the luxuriant pasture and this is then followed by low producers, such as dry
cows or sheep.
It has the following disadvantages:
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it requires a relatively large area of pastureland, e.g., 10 or more hectares
it may suffer from a lack of water during dry weather conditions.
Strip grazing
Strip grazing is most suitable for high quality pastures as animals will have a restricted intake if
pasture is poor. The advantages are similar to those for rotational grazing, except that there is less
selective grazing, the pasture is grazed more uniformly and there is less trampling and fouling
with dung. This type of grazing produces a high level of animal production. Efficiency of forage
use can be increased by 15 to 20 % on high quality pastures.
Continuous grazing
The advantages and disadvantages of this system are dependent on the seasons. In the rainy
season, there is an abundance of forage and pasture is normally under-grazed because the
stocking rate is relatively low. However, in the dry season, overgrazing can occur, and the sward
takes a longer time to recover and re-grow. During the dry season, animals may need to be
supplied with an additional sub-maintenance ration. Another disadvantage is the build-up of ticks
and intestinal parasitic worms on the pasture.
Deferred grazing
Deferred grazing provides a maintenance ration for animals during the dry season.
This system can be used by ruminant farmers in the tropics. It has disadvantages in that it only
provides a maintenance ration and taller grasses may smother the growth of legumes, creating an
imbalance in the grass/legume sward.
85. explain the importance of forages (grasses and legumes) in livestock feeding
In selecting forage plants (grasses and legumes), farmers need to consider:
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productivity: high-yielding varieties which have rapid growth and respond favourably to
nitrogen fertilisers
palatability: farm animals will eat more if the grasses are tasty
nutritive value: some plants are more easily digested than others, some are particularly
high in protein or minerals
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adaptability: plants need to adapt to soil and weather conditions (high rainfall in wet
season, drought in dry season so plants must be drought-resistant).
The nutritive value of forages is directly related to the stage of growth. As forage plants age and
grow to maturity, the crude fibre content increases and the protein content decreases. It is usual
to apply nitrogen fertilisers to pasture grasses to increase the protein content. Most green herbage
is rich in carotene, a precursor of vitamin A, and also in vitamin E and the B vitamins.
Grasses
Grasses used as herbage for farm animals can be divided into two groups (pasture and soiling) as
shown in Table 16.4.
Pangola grass (Digitaria decumbens)
Pangola grass is a native of South Africa. It is a perennial with long stolons, rooting to form a
turf. It grows best in well-drained moist areas, but it can withstand continuous close grazing,
flooding and drought. It responds favourably to nitrogen fertiliser and can be propagated by stem
cuttings or root divisions (setts).
Para grass (Brachiaria mutica)
Para grass is a native of tropical Africa and of South America, including Trinidad. It is a creeping
perennial with stolons and produces stems which grow to 2 m or more. It is very suitable for
moist, lowland pastures and provides excellent, palatable fodder when eaten young. It does not
stand up well to heavy or continuous grazing, but it grows well in combination with Centrosema
Elephant grass (Pennisetum purpureum)
Elephant grass, or napier grass (sometimes referred to as a king grass), is indigenous to Nigeria
and has spread throughout tropical Africa. It is a tall, tufted or bunched perennial growing 4 to
4.5 m high. It is high-yielding and palatable, with a high nutritive value when young and not too
fibrous. It is drought-resistant but cannot withstand heavy or continuous grazing. It is an
excellent grass for silage-making and soilage. It grows well with Centrosema and can be
established from stem-cuttings.
Guinea grass (Panicum maximum)
Guinea grass, a native of Africa, is found throughout the humid tropics and sub-tropics. It has
similar properties to elephant grass, but only grows 2 to 3 m high. It can withstand drought but
dies if heavily grazed. It is excellent for zero grazing and combines well with Centrosema and
Stylosanthes. It can be established by seeds or root-divisions (setts).
Guatemala grass (Tripsacum laxum)
This perennial grass grows tall and leafy, forming large clumps. It is droughtresistant but easily
uprooted by grazing animals. It is a good grass for silage-making and soiling, although it has a
lower nutritive value than elephant grass.
African star grass (Cynodon plectostachyus)
This is found throughout the tropics and sub-tropics, growing well in warm, humid climates. It is
a perennial with creeping stems which grow rapidly, providing quick coverage of bare ground
and forming a turf 120 cm high. It will grow on a range of fertile soils and is tolerant of close
grazing. It does not set viable seed and has to be established from cuttings.
Antelope grass (Echinochloa pyramidalis)
Antelope grass is a native of southern Africa and is a reed-like perennial growing 300 cm high. It
grows in swamps but is drought tolerant. It makes useful hay and silage and excellent dry season
grazing. The young growth is very palatable. In some parts of Africa, the grain is used as human
food.
Tanner grass (Brachiaria arrecta)
Tanner grass is a native of southern Africa and has been naturalised in the tropics and subtropics. It is similar to para grass, with which it hybridises. It can be propagated from stem
cuttings and is easily established to give complete ground cover. In contrast to para grass, it can
withstand heavy grazing. It has a high nitrate content and is toxic to cattle under certain
conditions.
Legumes
Pasture legumes are either herbaceous plants, such as kudzu or Centrosema, or shrubs, such as
Leucaena or Gliricidia. They are very important forage plants because they:
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fix or add nitrogen to the soil
help to maintain the fertility of tropical pastures
promote the growth of the pasture grasses
increase the palatability, digestibility and nutritive value of the forage grass and legume
combination.
The legumes are superior to grasses in protein and mineral content. Their nutritive value does not
decline as much with age or maturity as it does with grasses. The straws of the legumes are richer
in protein, calcium and magnesium than cereal straws and other grass crops.
However, large amounts of legumes in the forage mixture can cause scouring and bloat (an
excessive amount of gas in the digestive tract of the farm animal). For this reason, the legume
content of the forage mixture is kept around or below 50%. Also, young, succulent herbage
(grass and legume) is wilted before being fed to livestock.
Some legumes cultivated in combination with grasses, locally and regionally, are described
below.
Stylosanthes
There are several species of Stylosanthes used as forage plants. Style Caribbean (Stylosanthes
hamata) is a short-lived perennial legume which can grow in hot dry conditions. It will grow on
well-drained soils and is tolerant of heavy grazing. It can be planted with sown grasses but is
generally oversewn into native pasture after the pasture has been treated with fertiliser.
Stylosanthes guyanensis is suited to poor soils in high rainfall areas. It has a high nutritive value
if eaten before it flowers. It combines well with Guinea and para grasses and can be established
by seeds.
Desmodium (Sweethearts)
This is found throughout the tropics and is widely used as a forage legume. It is a trailing vine
and well-adapted to moist, tropical soils. It is grown in combination with savanna, Bermuda and
pangola grasses. It can he propagated by seeds.
Centro or Centrosema (Centrosema pubescens)
Centro is a leafy perennial which trails along the ground. It can be established from seed and
may be combined with Bermuda, Guinea, elephant and para grasses.
Kudzu (Pueraria phaseoloides)
This legume is very similar to Centro and combines well with many different grasses.
Leucaena (Leucaena leucocephala)
This is a perennial shrubby legume, which is deep-rooted and drought tolerant. It grows in welldrained soils in warm regions and needs at least 600 mm of annual rainfall. It can be interplanted
with elephant grass. It provides the highest quality feed of any tropical legume and has the
potential to produce the highest weight gains when fed to cattle. Its deep roots allow it to produce
new leaf after shallow-rooted grasses have run out of moisture.
Gliricidia (Gliricidia sepium)
Glyricidia is an evergreen shrub cultivated for green fodder. It can be interplanted with elephant
grass and is a source of protein.
Non-legumes
Other herbs and shrubs, such as mulberry and neem, may be used as forage for ruminants.
Mulberry (Morus genus))
Mulberry leaves are highly palatable and digestible to herbivorous animals. The leaves and
young stems can be harvested and fed to ruminants. The protein content is high, and this type of
forage has been used to replace some concentrates in the diets of farm animals.
Neem (Azadirachta indica)
Neem is a member of the mahogany family and a native of the Indian sub-continent; it has been
established in the Caribbean for over a century. It grows best where annual rainfall is 400 to 1200
mm. It is best known for its medicinal and pesticide properties. It has bitter foliage but is
browsed by goats and camels. Its foliage can be used as an emergency livestock feed.
Trichanthera
The leaves of Trichanthera (Trichanthera gigantea) can be eaten by pigs.
86. describe the measures used to feed ruminants when forage is unavailable
Pastures can produce good quality forage for ruminant livestock. However, on most farms the
pasture is rain-fed, producing high yields of palatable, nutritious forage during the rainy season
and lower yields of poorer quality during the dry season. Caribbean farmers have adopted
strategies to overcome this problem of forage conservation, so that their livestock have nutritious
forage all year round. There are three major forage conservation techniques:
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hay making
silage making
deferred grazing
Hay making
Hay making has two requirements: young grass with an abundance of leafy materials, together
with sunny and windy conditions. The process involves:
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cutting the grass at the desirable stage of growth
rapid drying, using sunshine and wind, so that moisture content is reduced from 80% to
15-20%
stacking and storing in a cool dry area of the barn
using it when required for feeding ruminant livestock.
Grass is cut before the flowering stage when its nutritive value, palatability and yield are high.
The cut grass is spread out in rows on the open field and turned at regular intervals for rapid,
uniform drying. When the moisture content has been reduced, hay is collected into small bundles
and stacked. Stored hay should be unblemished, unbleached and have a pleasant aroma.
Silage making
Silage consists of green forage crops which have been cut and preserved in a succulent, palatable
and nutritious condition for later use as feeding material for ruminant livestock. The nutritive
value depends on the growth stage at which the grass is cut, while the quality of the silage
depends on the fermentation process within the silo. The process of silage making is called
ensiling or ensilage, and the container in which it is made is called a silo. Silos may be of the
following types: pit silo, tower silo, clamp silo or stack silo.
Ensilage involves the following stages:
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cutting the grass or forage crop: this is done at the young, leafy immature stage and
wilted in the sun to reduce moisture content
filling the silo: cut mate rial is spread uniformly in layers in the silo
compression of the material: a four-wheeled tractor or heavy roller is used; this controls
respiration within the mate rial in the silo
addition of molasses: 3-4% by weight, diluted equally with water, sprayed evenly on to
the cut material to start fermentation
fermentation: aerobic bacteria convert carbohydrate into acetic acid and lactic acid
temperature control: temperature within the silo should be around 32-38°C; inadequate
compaction results in excessive respiration and overheating; it also creates conditions
favourable for bacteria to produce butyric acid (not desirable)
pH regulation: acidity needs to be at pH 4.2 or lower to suppress the production of
butyric acid which makes the silage foul-smelling and unpalatable.
Over-compaction of the silage can also create conditions in which butyric acid is formed by
bacteria.
In addition to feeding ruminants hay and silage, farmers can supplement animals' diets with
commercially prepared concentrates to compensate for the lack of fresh forage.
Housing
87. explain the principles that govern housing requirements for farm animals
Several factors, including cost of labour and building materials, are involved in the design and
construction of housing for farm animals. Other major factors are:
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purpose: type of farm animal, e.g., rabbits, poultry
location (site chosen): stability of ground; well-drained and not prone to flooding or
landslides; proximity to pastures, field plots, manure heaps and other farm buildings
orientation to give protection from the elements (see Figure 17.1): pens are constructed
lengthwise in a north-easterly direction, protecting animals from direct sunlight during
the morning and afternoon
ventilation: good ventilation disperses heat, foul gases (odours) and moisture; promotes
air circulation and temperature control
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lighting: natural light is needed during the day; electric lighting is necessary at nighttime; good lighting helps to keep away predators and vampire bats
predator control and security measures: chain-link fences with padlocked gates around
pens; wire mesh in upper parts of the walls to the ceiling; flood lighting at strategic points
around the buildings from dusk to dawn; ceiling lamps within the pen; security measures
to keep away stray cats, dogs, vampire bats, mongooses, rats and thieves
sanitation: designed for easy cleaning with rough, concreted and sloping floor, channel
for speedy removal of effluent into a slurry pit or biogas digester, and an appropriate
pathway for the removal of solid wastes to the manure heap using a wheelbarrow
safety: footbaths at entry points to the pen; grills or covers over deep drains, channels and
pits; several wide exits for speedy removal of farm animals in case of fire or other
emergency; fire-fighting equipment located conveniently.
Materials
Materials used for farm buildings and animal housing may be grouped into those available
locally and those that are imported. Local materials include lumber (from local trees such as
mora, teak, mahogany, cedar, Caribbean pine), aggregates (gravel, sharp sand, cement), metals
(iron and steel beams, aluminium/zinc roofing sheets), pvc used for pipes and guttering, and clay
and concrete for bricks and tiles. Materials are imported from Brazil, Canada and the USA, and
include lumber (pitch pine, plywood, chipboard), metals (galvanised roofing sheets and pipes)
and ceramics (tiles, wash basins, sinks).
Properties of materials
Table 17.1 summarises some materials for use in the construction of animal housing.
Lumber should be hard, strong and durable (long-lasting). Some timbers, such as greenheart,
mora and wallaba, are more durable than others. Teak, greenheart and cedar are more resistant to
termite attack, whereas Caribbean pine, plywood and white pine are susceptible. Some timbers,
such as Caribbean pine and white pine, rot readily when partially buried in the soil, so should be
avoided for use as posts. The durability can be improved by treatment with paint, creosote,
solignum, pressure or heat.
Iron and steel are hard, strong, resistant and heavy. They have tensile strength (do not break
under tension), so are used as the framework for concrete posts and beams, decking or raised
floors and roofs. These metals do rust when exposed to the atmosphere and rain, so they are
treated with zinc oxide to prevent corrosion (galvanised). The coating prevents rusting for some
time, after which protection is given by regular painting.
Aluminium and zinc are also hard and strong metals, but they are lighter and do not rust so are
more durable. They are moulded into roofing beams and sheets, frames for doors and windows,
and louvre blades for windows. The plastic materials used in buildings are tough, rust-resistant
and durable, but they can be broken. These materials can be moulded readily and are most useful
for pipes and fittings for electrical and plumbing systems. If breakages occur, it is much easier to
mend them than it is to mend an iron pipe.
Concrete is used for foundations, floors, drains and pathways. It is tough, hard and waterproof. It
is usually moulded into a non-skid, rough finish which is sloped for ease of cleaning and
washing.
88. describe the housing and space requirements for broilers, layers and rabbits
Poultry pens should have the following features:
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situated in a well-drained area
constructed so that they are about 10 m wide and a convenient length
oriented lengthwise in an east-west direction to keep out sunshine
made of lumber, with an aluminium/zinc roof with eaves extended 1 m to keep out rain
a slightly graded concrete floor for easy cleaning and washing
a brick wall 30 to 45 cm high to retain litter in a deep litter system
enclosed with wire mesh from the top of the brick wall to the ceiling
barricaded with feed bags, especially on the windward side to keep out rain and cold
draughts
a doorway, 1 m wide, to allow the passage of a wheelbarrow for transporting feed and
waste
sufficient ventilation and suitable lighting.
Deep litter systems
This type of system is commonly used for the rearing of broilers and layers. In a deep litter
system, poultry are provided with litter material to a depth of 10 to 15 cm on the floor of the pen.
Local materials, such as bagasse, lawn grass trimmings, chopped rice straw, dry grass and wood
shavings, are used as litter. The litter is stirred once or twice a week and kept dry at all times.
When calculating the number of birds, it is usual to allow 4 to 5 birds per m 2 for broilers and 3
birds per m2 for layers. In addition, perches are provided for roosting and the layers have nest
boxes for egg-laying.
Battery systems
In a battery system, birds are housed in cages. This system is mainly used for layers where land
is limited. The cages have the following features:
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made with sturdy wire
a trough for food and water on the outside of the cage
an outwardly sloping floor to make egg collection easier
a removable tray beneath the wire floor for the collection of droppings.
A cage for a single hen should measure 36 cm long, 30 cm wide and 36 cm high. Cages designed
to hold three hens should measure 90 cm long, 36 cm wide and 36 cm high. The cages may be
stacked in three or more tiers.
Rabbits
The place where rabbits are reared is called a rabbitry. It consists of cages, called hutches, which
are built to accommodate a single rabbit in an individual hutch or many rabbits in a communal
hutch. Hutches vary in size but an individual hutch measures 75 cm long, 60 cm wide and 40 cm
high. Communal hutches can be 120 cm long but have the same width and height dimensions as
an individual hutch. The floor is usually 1 m above the ground. Hutches may be constructed of:
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wire mesh only (if they are to be used inside another building)
wire mesh, wood and roofing material if they are to be sited outdoors under a tree.
The wire mesh should have 1.5 cm2 holes. Since rabbits are gnawing animals, wire mesh is
placed on the inside of the wooden frame. Nest boxes are placed in the hutches of pregnant doe
rabbits. Hutches are specially designed so that they:
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are well-ventilated
protect the rabbits from rain, sun and cold draughts
allow droppings to fall through the wire mesh floor: to the ground in outdoor hutches, to
deep litter beneath in indoor hutches, or on to a tray for droppings beneath the wire mesh
floor
are durable and easy to clean.
89. explain the factors to be considered in the siting and establishment of an apiary and a fish
farm
Bee production
Bee keeping and the production of honey, known as apiculture, is a useful form of agriculture in
developing countries. It is not too expensive to set up and it provides valuable food. Swarms of
wild bees can be collected and kept in hives made of local materials. Alternatively, colonies of
bees can be purchased. The hives can be placed in orchards or where there are sources of nectar
and pollen, such as gardens and vegetable plots. Bees will thrive provided that they are kept safe
and dry. Hives should be in the shade, protected from the wind and rain and near a source of
fresh water. A group of hives is known as an apiary. Traditionally, hives have been made out of
local materials, such as bark, clay pots, straw or woven baskets. There are three basic choices of
hive:
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local-style fixed comb: clay pots can be used for these hives; several pots grouped
together and placed on a stand will provide somewhere for the bees to build a comb and
also a brood box, where the queen bee lays her eggs
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top bar hive: usually made of wood, but can be constructed from bamboo, straight sticks,
woven matting; needs to be plastered with mud or cow dung to make waterproof and to
prevent entry of ants and hive beetles; the top bars are made of bamboo or straight sticks
and a stick of wax is fixed to the underside of the bars to guide bees to build their comb;
this hive can be hung from a tree and moved from place to place
frame hive (moveable comb): typically constructed of wood; some are concrete and are
cheaper than wooden hives; this hive is used by commercial beekeepers.
Frame hive
A frame hive consists of:
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a floor forming the base of the hive, with a landing platform for the bees to enter the hive
a brood box containing frames
a super with frames which form the honey store; this is separated from the brood box by a
queen excluder
a roof
The brood box and the super are similar in construction, but the brood box is usually deeper.
Inside the brood box are the frames on which the queen lays her eggs. The super also contains
frames, but these are where the bees store food and honey. The queen excluder prevents the
queen from getting into the super and laying eggs there. The excluder also makes it easier for the
beekeeper to extract honey. The frames are made of wood surrounding a wax foundation on
which bees build the cells of the comb in which the honey is stored. The frames are held the
correct distance apart in the brood box and in the super by metal ends. This enables the frames to
be removed for inspection and for the extraction of the honey from the super.
To begin with, one brood box and one super are sufficient, but as the bee colony increases in size
more supers can be added.
Although a frame hive is more expensive to buy or make, it is more convenient for the beekeeper
and makes extraction of honey easier. Oil drums and plastic containers can be used, and frames
can be made to fit these.
Protective clothing must be worn by people dealing with bees, so that there is less risk of being
stung. The head and face are protected by a hat and veil. A bee suit, to which hat and veil can be
attached, is also desirable. Bee stings can penetrate jeans and thin socks, so if a bee suit is not
available then thick clothing should be worn. Hands can be protected by gauntlets which extend
to the elbows.
In addition to the hives and protective clothing, equipment is needed for the extraction and
marketing of honey. If the honey is to be marketed commercially, then steel or plastic extractors
are required.
Fish farming
Aquaculture refers to the cultivation of selected aquatic plants and animals in water in specially
designed areas, using appropriate management principles and techniques. There are three main
types of aquatic environment:
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freshwater farming: tilapia rearing; shrimp farming; cascadura rearing; rearing of black
conches; cultivation of water lilies; ornamental fish farming
brackish water farming: prawn farming; oyster farming; tilapia farming
salt or seawater (marine) farming: shrimp farming; sea moss cultivation; lobster farming;
turtle farming.
Aquaculture has an important role to play in developing the local economy because it:
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increases fish production
satisfies the nutritional needs of the population
promotes employment in local communities
generates additional income for farmers
uses resources (land, water, humans) more effectively
means that fish and fish products do not have to be imported.
In establishing a freshwater aquaculture system, several factors should be considered, e.g., the
types of fish to be farmed (such as tilapia or cascadura), the production system and the types of
ponds.
Production systems may be intensive with high stocking rates (10 to 40 fish/m3), semi-intensive
with a moderate stocking rate (4 to 5 fish/m 3), or extensive with a low stocking rate (1 to 2 fish/
20 m3).
Extensive systems
Extensive systems involve fish being taken from a local river and placed in ponds. Animal
manure is used as a fertiliser and promotes growth of pondweed, which oxygenates the water as
well as providing food for the fish. This system is cheap as it does not require much labour or
additional food for the fish.
Intensive systems
Intensive systems involve tanks or ponds in which conditions are strictly controlled. The
temperature is kept within the optimum range for the type of fish and the oxygen levels and pH
are carefully monitored to ensure maximum growth rate. Care is taken to ensure that organic
matter from farm sewage or silage does not get into the water. Organic matter promotes growth
of blue-green algae that can be toxic to fish. Algal blooms can also result in blockage of pipes
and waterways.
Ponds may be concrete or earthen. The best earthen ponds are of a clay soil type. Those built on
other soil types need to be lined with durable plastic and compacted to prevent leakage. Most
will be 1.5 to 2 m in depth, the number and size depending on the scale of the project and the
production system. Ponds must be capable of holding unpolluted water all year round. They
should be sited where there is some shade.
In a large fish farm, a series of ponds is constructed with walkways between them so that there is
access for cleaning and feeding. The ponds are linked to common inlet and outlet channels for
water flow. The series of ponds allows for fish of different ages and stages of growth to be reared
so that there is a continuous supply for market.
There are government aquaculture project sites, such as the Sugar Cane Feeds Centre, from
which young fish, called fingerlings, can be obtained. Farmers with established aquaculture
enterprises, where fish are allowed to breed, may also be a source of fingerlings.
The choice of feeds and the method of feeding will depend on the fish species and the production
system chosen. Feed millers, such as National Flour Mills, or feed depots can supply sinking or
floating fish feed in the form of pellets or feeds for other animals (broiler starter or pullet
grower). Tilapia can eat 3 to 5% of their body weight in feed daily. They can convert 1.8 to 2.2
kg of feed into 1 kg of bodyweight. Tilapia should be fed at least twice daily.
Setting up
When setting up a fish farm, the following management practices need to be considered:
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protection: fences and bird nets protect against predators such as alligators and birds
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aeration: the demand for oxygen increases with the number of fish in the pond, so
intensive systems with high stocking rates need to have equipment to aerate (oxygenate)
water in the pond
fertilising: fertilisers are added to water to encourage growth of algae which is a source of
food for the fish
sampling: growth of fish can be monitored weekly by weighing a sample of
approximately 2.5% of the population in the pond
observations of water quality, health of fish, behaviour and mortality should be made
daily
record-keeping: records should be kept of all observations, sampling weights, feeding and
aeration on a regular basis.
Harvesting
Harvesting takes place when fish have reached their ideal market weight (0.5 to 0.75 kg for
tilapia). The time taken to reach this weight depends on the age of the fingerlings, feed quality
and feeding regime. Generally, 2-month-old fingerlings raised in ponds can be harvested in 4 to 5
months. After harvesting, live or chilled fish are sold directly to consumers or taken to district
markets. Dressed fish or fish fillets are supplied to supermarkets, restaurants, hotels or exported
to niche markets abroad.
Coastal aquaculture
Coastal ponds can be used to farm marine shrimp, but this depends on the tides filling and
emptying the ponds. Marine shrimp and oysters are farmed intensively in the Bahamas, but few
other regions in the Caribbean have developed this type of fish farming extensively. Marine
tilapias are farmed in cages off the coasts of some islands.
Animal Genetics, Breeding and Reproduction
90. list the breeds of each class of animals commonly reared in the Caribbean
There are several classes and breeds reared in the Caribbean (see Table 18.1).
Many breeds have been brought to the Caribbean from other parts of the world. These breeds
have been chosen for the quality of their meat or other products, and also for their ability to
tolerate the climate together with resistance to pests and diseases.
Some breeds have been developed especially for the Caribbean region by crossbreeding (when
two different breeds are bred). The breed of cattle called Jamaica Hope was developed in
Jamaica by crossing Zebu cattle from India with Jersey cattle from Europe. The resulting breed is
a good milk producer and resistant to some diseases. Similarly, Jamaica Red and Jamaica Black
cattle were developed from Aberdeen Angus cattle for good meat production. In Trinidad and
Tobago, the Buffalypso was developed by crossing different breeds of River buffaloes. The
resulting meat is of a higher quality than the top cuts of prime beef and breeding stock have been
exported to other Caribbean countries. The Barbados Blackbelly sheep are reared for their meat
and are probably derived from sheep brought by settlers to the islands. They are tolerant of heat
and have coats of coarse hair, not wool.
91. state the purpose for which the different breeds of animals are reared
The major roles of animals on the farm are to:
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provide food
supply power for ploughing (bullock, buffalo, mule) and transport (mule, donkey,
buffalo, horse, bullock)
supply raw materials
create employment opportunities and provide farm income
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provide recreation and serve as pets
provide opportunities for agricultural research.
The provision of food involves the production of milk, meat and eggs. The major classes and
breeds producing these commodities are listed in Table 18.2.
Supply of raw materials Raw materials from farm animals include:
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dung/droppings from all classes of animals: used as manure
skin, pelts, leather: the skins can provide leather and pelts are used for manufacture into
garments and furniture; sheep are not kept in the Caribbean for their wool as the wool
breeds do not suit the climate; goats produce hair for carpets and cloth, in addition to
their skins for leather
dung of pigs and cattle: used to generate biogas.
Pets
Many animals are kept as pets and for recreational purposes. Rabbits, goats and sheep may be
kept as pets, whereas horses are bred for racing and riding. Other pets are cats and dogs: these
also protect farm animals from predators and vermin.
92. explain simple Mendelian inheritance and common terms in genetics
To appreciate the way in which breeds of farm animals may be improved, we need to understand
how different characteristics are inherited. Refer back to Chapter 11 and revise cell division, the
nature of genes and chromosomes, and the common terms used (genotype, phenotype,
homozygous, heterozygous, dominant and recessive).
In Chapter 11, genetic inheritance in plant breeding was explained. Meiosis occurs during
gamete formation and introduces variation, so that after fertilisation the offspring are not
genetically identical to each other or to their parents. In the same way that different varieties of
crops have different genotypes, so do different breeds of an animal species.
We can increase the productivity of a plant crop or a breed of animal by crossing individuals with
favourable characteristics in a breeding programme. For example, in the development of Jamaica
Hope cattle, Jersey cattle with high milk yields were crossed with Zebu cattle from India and
Holstein cattle, also high milk yielders, from Europe. The resulting breed produces a high milk
yield on the poor pastures associated with the tropical climate of the region. These cattle tolerate
heat and have a high resistance to ticks and the diseases they carry.
Inheritance and coat colour
The way in which simple Mendelian inheritance works can be shown by considering coat colour
in two breeds of cattle. Lincoln Red cattle have red coats and Hereford cattle also have red coats
but white faces. Figure 18.8 shows a Hereford cow. The presence of the white face is due to the
dominant allele (W) of a gene. Hereford cattle are homozygous dominant for this characteristic
(WW). When a farmer mated Lincoln Red cows with a Hereford bull, the offspring all had white
faces. The farmer kept one of the male offspring of this cross.
When it was mated with Lincoln Red cows, half the offspring had white faces and half did not.
We can show what is happening by using genetic diagrams. Let W represent the dominant allele
for white face and w represent the recessive allele (this does not result in a white face). The
genotype of the Lincoln Red cow is ww and the genotype of the Hereford bull is WW. The
diagram in Figure 18.9 shows us what is happening in terms of genes.
If a homozygous Lincoln Red cow is now crossed with a heterozygous Hereford bull (Ww) we
get offspring as shown by Figure 18.10. Half the offspring will have white faces.
93. explain different breeding systems in animal production
Breed
A breed is a group of animals of the same species which have certain characteristics in common.
These characteristics are usually physical ones, such as coat colour or shape of the body, but they
may also be behavioural characteristics, such as docility. Different breeds have developed as a
result of the selection of desirable characteristics by farmers and breeders or by crossbreeding. A
breeding system involves the mating of a male animal with a female animal. Both animals are
chosen for their desirable characteristics.
When a breeder wants to produce more 'suitable' animals, he must decide which characteristics
are important. Variation among individual animals of a particular breed is influenced by their
genotype and the environment. For example, dairy cows are bred for their high milk yields, but if
put on poor pasture their yields will not be as high as those fed on a better diet. If the breeder is
hoping to breed an animal that will increase its productivity, he needs to know what proportion
of the desired characteristic is influenced by genotype, rather than by the environment.
The effect of genes on a characteristic is referred to as heritability. Many important
characteristics, such as milk yield, carcass quality and rate of growth, are continuous controlled
by more than one pair of genes. These characteristics show continuous variation and there may
be a wide range of values across the breed. Each gene may have a small effect on milk yield, for
example, but several genes combine to have a cumulative effect. It is possible to calculate the
heritability of a characteristic, such as milk yield, by keeping records of the volume of milk
produced by each cow and then determining the average for each individual and the average for
the herd. Cows that have averages above the herd average would be the ones to breed from if the
farmer wants an increased yield. (When referring to different types of crop plants of the same
species, the term variety is used instead of breed. Varieties, or cultivated varieties, are often
referred to using the shortened form, which is cultivars.)
Crossbreeding
Cross breeding occurs when an animal is mated with another animal of the same species but of a
different breed. For example, Hereford cattle may be mated with Aberdeen Angus cattle to give
offspring with an increased growth rate. Animals that are cross bred often show increased vigour
and productivity. The genes from the two breeds are combined. Characteristics controlled by the
dominant genes from both breeds tend to be expressed.
Inbreeding
Inbreeding occurs when animals of the same breed are mated with one another. These animals
will be closely related and genetically similar to each other. Animal breeders use inbreeding to
produce superior offspring (in the short term) and to maintain desirable characteristics within the
breed. However, there are some risks attached to inbreeding. If inbreeding is used for many
generations, there is actually a decrease in desirable characteristics and an increase in undesirable
characteristics. This is known as inbreeding depression. Inbred animals may show a decreased
resistance to infection, be smaller in size, show physical defects and have a shorter life span.
Upgrading
Upgrading involves the crossing of native, or local, breeds with breeds from other countries or
regions of the world. Farm animals that thrive and have high productivity in a temperate climate,
such as found in Europe, do not always adapt well to a tropical climate. Their food sources may
differ, and they cannot tolerate the heat as well as the local breeds. They also have less resistance
to the pests and diseases which affect local breeds. For these reasons, crossbreeding of local
breeds with high-producing imported breeds can have advantages. Desirable characteristics of
the imported breed can be introduced into the local breed. A good example is development of the
Jamaica Hope dairy cattle and the Jamaica breeds of beef cattle.
Back-crossing
Back-crossing is the term given to the crossing of a hybrid organism with one of its parents. It
can be used in both plant and animal breeding programmes but has probably been more
frequently applied in the development of crop plants. This type of cross is carried out to obtain
offspring which are similar to the parent with the desirable characteristic.
In a cross between a heterozygous Hereford bull and a Lincoln Red cow described in Figure
18.10, half the offspring would be homozygous (ww) for the recessive gene and not show the
white face associated with the Hereford breed. It would be easy to select these offspring from the
rest. If, however, the breeder wanted to keep the dominant allele, then the heterozygous offspring
would need to be backcrossed with the homozygous dominant parent, as shown in Figure 18.11.
In Figure 18.11, the characteristic is a visible one and controlled by a single gene, but most
characteristics are not easily visible and are controlled by a number of genes.
Back-crossing can maintain desirable characteristics in a breed and does not introduce new
genes. However, it does not work well for characteristics such as growth rate, nor does it work
for recessive genes.
94. explain the advantages of crossbreeding
Hybrid vigour (heterosis)
Crossbreeding involves mating animals from different breeds of the same species, and it
combines the genes of the two breeds. The resulting offspring are referred to as hybrids and there
is an increase in heterozygous genes. Hybrid offspring may be more fertile and have a longer
lifespan than their parents. The increased fitness of the hybrid generation is called hybrid vigour
or heterosis.
Most desirable characteristics are controlled by dominant genes and hybrid vigour is due to the
increase in heterozygous genes. Undesirable characteristics are often controlled by recessive
genes. An increase in heterozygous genes means that these characteristics do not show in the
hybrid offspring.
An example of how an increase in heterozygosity can benefit a breed can be shown by crossing
two breeds of pigs. Breed X sows produce large litters, but the survival rate of the piglets is low.
Breed Y sows have fewer piglets in each litter, but the survival rate of the piglets is high. Large
litters are controlled by the dominant allele A and percentage survival is controlled by the
dominant allele B. If a pure-breeding sow from Breed X is crossed with a pure-breeding boar
from Breed Y, then the piglets will show hybrid vigour. This is shown in Figure 18.12.
Examples of hybrid vigour in farm animals include:
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milk yield and butterfat content of milk in dairy cattle
carcass composition and weight gain after weaning in beef cattle
litter size and growth rate in pigs
carcass weight in sheep.
Disease resistance
An inbred resistance to disease in farm animals means that farmers depend less on the use of
drugs to treat diseases. There is therefore a decreased risk of these drugs getting into human
food. The benefits to farmers are that veterinarian's bills and production costs are lower. In
addition, disease resistance reduces the chances of pathogenic organisms becoming resistant to
drugs.
Many people think that if animals are kept healthy and reared under good conditions, they are
less likely to suffer from diseases. This is true, but resistance to some diseases is also inherited.
It would be difficult to breed animals that are resistant to all diseases. However, there has been
some progress in selecting breeds which show resistance to conditions such as:
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mastitis and respiratory diseases in cattle
Salmonella and E. coli in pigs
footrot and scrapie (a viral disease) in sheep
certain parasites.
The Jamaica Hope breed is an example of selection for disease resistance (see page 264). Zebu
cattle have some resistance to parasitic ticks and the diseases they carry. When Zebu were
crossed with Jersey cattle, the resulting hybrids also showed increased resistance to ticks.
Improved production
Crossbreeding will result in improved production in farm animals if breeds with desirable
characteristics are chosen. Crossbreeding results in increased vigour of the offspring; it also
improves survival rate and leads to faster growth rates. A farmer or animal breeder will always
choose the fittest animals from which to breed, so continuing the improvement of the stock.
95. explain the genetic improvement principles
In attempting to improve breeds of farm animals it is necessary to:
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identify desirable characteristics
keep accurate records of animal performance
select animals for breeding.
These principles of genetic improvement have been used by animal breeders for many decades,
but an understanding of genetics has increased the rate of improvement. We can now identify
which characteristics are inherited and which are due to the effects of the environment.
Desirable characteristics are those which increase productivity for the farmer. More income can
be derived from hens that lay more eggs, cows that produce more milk, and beef cattle that have
a fast growth rate and a good carcass shape.
Performance testing
Performance testing involves comparing the productivity of animals kept under the same
conditions. It applies to characteristics which can be measured, such as milk yield, number of
offspring and survival rates. Records of performance are useful, not only for identifying which
animals are good producers but also for the farm accounts. The benefits of record-keeping have
already been described in Chapter 7.
Embryo transfer
The selection of animals for breeding is mainly based on their performance. Good dairy cows
have traditionally been used for breeding, but the number of calves produced in their lifetime is
about eight, of which half could be male. Nowadays, 'desirable' cows can be made to produce
many embryos which are transferred to the uterus of another cow or deep frozen for later
implantation. This technique is known as embryo transfer. It increases the number of offspring
from the 'desirable' cow.
Progeny testing
Desirable female characteristics, such as milk yield in cattle, cannot be assessed directly from a
bull's phenotype. So, bulls are mated with several cows and the performance of their daughters is
compared in a process called progeny testing. If the outcome is favourable, then the bull can be
mated and pass his genes on to a large number of offspring. Use of artificial insemination, where
one bull's semen can be used to fertilise many cows, means that a good bull may produce
thousands of offspring in a year.
Heritability
When assessing fitness for breeding, the heritability has to be considered. Heritability is the
effect of the genes on the desired characteristic. If a breeder knows the approximate heritability
of a characteristic, they will have some idea as to whether selection for improvement of that
characteristic is likely to be successful. The higher the percentage heritability is, the greater the
chance that selection for the characteristic will result in improvement. For example, postweaning increase in weight in sheep has a heritability of 60%, but fleece weight has a heritability
of 17%. Of course, there will always be variation within a breed of farm animals and that
variation will be different in different groups of the same breed.
96. describe the process of artificial insemination (AI) in farm animals
Mating in livestock farming refers to the bringing together of a mature male and female animal
of the same species for the purpose of breeding. Female animals which come on heat may be
bred or serviced naturally by the male (boar, bull, ram or buck). As an alternative, semen from
the male can be obtained and introduced into the reproductive tract of the female on heat in the
process of artificial insemination (Al). This is a technical process which needs to be carried out
by a trained inseminator. Artificial insemination is carried out in cattle, sheep, goats and pigs.
The semen is collected from pedigree or proven male animals, chosen for their desirable
characteristics. An electrical stimulation device or a massage method may be used to make the
male ejaculate into an artificial vagina which collects the semen. A single ejaculation can have a
volume of 3.5-5.0 cm' and contain 15 x 106 sperm. The sperm count of the semen is determined
and quality control checks detect any abnormalities or diseases. The semen is then diluted with a
solution containing:
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sugar
salts which maintain the correct pH
glycerol to protect the sperm against the effects of freezing
antibiotics to prevent the growth of bacteria.
The semen is divided into small quantities, 0.25 cm3 to 0.5 cm', and packed into disposable
plastic straws. The straws are stored by freezing in liquid nitrogen at -196°C. The straws can be
used to service hundreds of female animals (cows, ewes, sows) worldwide. Before AI is carried
out, the straw containing semen is thawed and placed into a glass or plastic pipette. The pipette is
inserted into the vagina of the female animal on heat. The inseminator, wearing long plastic
gloves, places a hand into the rectum to manipulate the reproductive tract and guides the pipette
so that semen is deposited beyond the cervix into the uterus (see Figure 18.14).
For AI to be successful, it is important that signs of heat are detected, and that insemination takes
place at the best time. In cows, oestrus (the period on heat) lasts between 12 and 16 hours. The
optimum time is between 5 and 20 hours after the beginning of oestrus, because ovulation occurs
10 to 12 hours after the end of oestrus.
97. evaluate the use of A.I. in farm animals
The main advantages of AI are as follows:
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farmers are more motivated to keep records
an improvement or upgrading of the farmer's stock of animals
it removes the risks involved in rearing dangerous male animals, e.g., bulls
the costs to the farmer are less than the cost of rearing a male animal to maturity
female animals do not need to be taken to the breeding station for servicing
the spread of venereal diseases is reduced or prevented
young females, such as heifers, are prevented from physical injury during mating due to
the weight of mature bulls
semen from a pedigree male can be used to service hundreds of females
semen from injured males or males that cannot mount females can be used
frozen semen can be stored and used for many years, even after the death of the male
animals.
The disadvantages include:
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the cost of setting up and maintaining the necessary facilities
the requirement for special equipment and skilled personnel, including trained
inseminators
the maintenance of semen storage and inspection facilities: the frozen semen has to be
monitored regularly to detect loss of viability of the sperm
failure of the insemination to result in a pregnancy: farmers may not respond quickly
enough to the signs of oestrus in the females; cows may come on 'silent' heat which is not
easily detected by the farmer but would be readily identified by a bull.
One disadvantage of the widespread use of AI in dairy cattle is that concentrating solely on
desirable characteristics could result in a loss of genetic variation. The techniques of diluting and
freezing semen mean that fewer bulls need to be kept and there is a danger of inbreeding
depression.
98. differentiate among the terms: ovulation, fertilization, gestation, oestrous cycle, kindling,
parturition, farrowing.
The oestrous cycle
The oestrous cycle is a sequence of events, controlled by hormones, occurring in female
mammals. It is the number of days from the beginning of one heat period (oestrus) to the
beginning of the next heat period. The heat period is the length of time during which the female
farm animal is sexually receptive to the male farm animal. Once puberty is reached, female farm
animals come into heat at regular intervals. It is only during the period of heat that the female
allows herself to be serviced by the male. Heat occurs as a result of the large amount of the
hormone oestrogen, produced by the ovaries, circulating in the blood. Ovulation is the release of
an ovum from the ovary and is closely associated with the heat period. It usually occurs during
oestrus or shortly after. Mating during this time can result in fertilisation and pregnancy. The
oestrous cycle (see Figure 18.16) can be divided into four phases:
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proestrus: influenced by oestrogen which prepares the reproductive system for oestrus
and stimulates the growth of ovarian follicles and the development of ova
oestrus (the heat period): influenced by oestrogen; causes the female to be sexually
receptive for mating; may result in ovulation
metoestrus: ovulation may occur at the beginning of this phase; after an ovum has been
released from its follicle a corpus luteum develops; the hormone progesterone begins to
be produced by the corpus luteum; less oestrogen is released
dioestrus: if fertilisation does not occur, the corpus luteum breaks down; there is a short
period of inactivity before a new proestrus phase begins. The duration of the oestrous
cycle and the time of ovulation vary among the classes of livestock (see Table 18.3).
Signs of heat
When female farm animals come on heat, they usually display signs which are recognised by the
farmer (see Table 18.4). It is important to look out for these signs so that the females can be
serviced by the males at the correct time for fertilisation. This is particularly relevant to cattle
because milk production depends on the cows’ producing calves.
Fertilisation
Fertilisation is the process in which the male gamete (sperm) fuses with the female gamete
(ovum) to form a zygote which, through cell division, becomes the embryo. In farm animals,
fertilisation (conception) can only occur when the female animal comes on heat, ovulates and is
mated or artificially inseminated. At the time of mating or artificial insemination, large numbers
of sperms are deposited in the female reproductive tract and swim up the oviduct towards the
ovum. Fertilisation occurs halfway down the oviduct when one sperm fuse with an ovum shed
from the ovary. The fertilised egg, now called a zygote, moves into the uterus where it becomes
implanted in the wall and eventually develops into the offspring.
Gestation
Gestation is the period between conception (fertilisation) and the birth of the young (parturition).
It varies in length with the different classes of farm animals (see Table 18.5). Throughout the
gestation period, pregnancy is maintained by the corpus luteum in the ovary which produces the
hormone progesterone. The farmer can recognise that his animals are pregnant because:
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there is an absence of heat (the non-pregnant cow would show signs of heat 19-23 days
after insemination)
the abdomen changes in size, becoming wider or 'bellying down'
the mammary organs (udders, teats, milk veins) develop.
The farmer can determine pregnancy in cows by getting a veterinarian or a trained livestock
technician to palpate the uterine horns 3 to 4 months after mating. This is done through the
rectum and enables the developing calf to be felt. More recently, pregnancy detection kits have
been developed. These measure progesterone levels in milk samples, and these can be used by
farmers. These kits are accurate, inexpensive and can be carried out in early pregnancy, so the
farmer can organise another insemination if the cow is not pregnant.
During pregnancy, the embryo becomes implanted into the wall of the uterus and membranes
develop around it. The placenta develops and enables nutrients and oxygen to pass from the
mother to the growing embryo, now called a foetus. Waste materials from the foetus pass across
the placenta into the blood of the mother.
Parturition
Parturition (the birth process) occurs at the end of the pregnancy and is the time when the female
gives birth to her young. This process is influenced by hormones, such as oxytocin and relaxin.
Parturition can be divided into several stages:
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just before parturition, the animal may become restless, seek out a quiet area, try to
urinate frequently; in cows, there is a thick mucus discharge from the vulva
uterine contractions occur as the result of the secretion of the hormone oxytocin
the cervix and pelvic region dilate under the influence of relaxin
the offspring is delivered through the birth canal
the placenta (after-birth) is delivered shortly after the offspring.
The farmer or a farm attendant should always be present at parturition to help. It may be
necessary to:
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remove mucus from the mouth and nostrils to enable the young to breathe easily
dry the young if the mother has not already done so
make sure that the umbilical cord is not wrapped around the neck of the young
sever the umbilical cord, using the correct procedures
make sure that the mother suckles the young soon after birth so that they get the
colostrum (first milk after parturition) which provides antibodies.
Kindling
Kindling is the term used to describe the process of giving birth in rabbits. It takes place 30 days
after a successful mating of the doe with the buck. About 5 days before the doe is due to kindle,
she will carry straw around and build a nest. A nest box should be placed in the rabbit pen 3 days
before kindling is due.
Farrowing
Farrowing is parturition in pigs and takes place about 115 days after mating. Two weeks before
farrowing, the mammary glands of the sow develop, the teats enlarge and veins supplying the
udders become prominent. The farrowing process lasts 3 to 8 hours, with piglets delivered at 10to-20-minute intervals. When all piglets have been delivered, the placenta is expelled.
99. describe the process of egg formation and incubation in poultry
Egg formation
Egg formation takes place in the reproductive tract of a hen which consists of a single ovary and
oviduct (see Table 18.6). The oviduct is a long tube divided into several sections, each with a
distinct function.
A hen's egg consists of an ovum (the egg cell) surrounded by yolk, albumen, the shell
membranes, the shell and the cuticle. Each part of an egg is laid down in a different section of the
oviduct and it takes 24 hours for an egg to pass from the ovary, through the oviduct to the vent
(cloaca).
An ovary can contain up to 12000 ova (egg cells) and it takes around 10 days for an ovum to
mature into a yolk. The yolk contains lipids and proteins and is yellow. The ovum is on the
surface of the yolk and can be seen as a small white structure, called the germinal disc. Under the
influence of hormones, the ovary releases mature ova into the top part of the oviduct (called the
infundibulum). The functions of the different parts of the oviduct are described in Table 18.6.
Incubation
Incubation is the process of providing the necessary conditions for the hatching of fertile eggs. It
is important because it enables the farmer to obtain new stock (chicks) for the production of
meat, eggs and feathers. It is an important 'farm-support' industry, supplying chicks for farmers
to raise as broilers or layers, as well as providing for the development of new strains of poultry
by breeding. Fertile eggs can be incubated naturally, using a broody hen, or artificially in an
incubator.
Natural incubation
This system is still favoured by small farmers in rural communities. It involves the use of a
broody hen which has just completed a laying-cycle. She sits on a clutch of 10-15 eggs in her
nest and provides them with warmth for the development of the embryos and their eventual
hatching. There are several factors which can influence this process, including:
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nesting environment: a cool, quiet, well-ventilated and darkened area encourages the hen
to lay and incubate
curvature of the nest: the hen moves her body and feet in a circular manner to prepare a
nest that is bowl-shaped; this brings all the eggs close together so that they are warmed
by the body of the hen
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clutch size: normally the farmer allows the hen to lay and incubate 10-15 fertile eggs
temperature: warmth is essential for development of the embryos; the hen's normal body
temperature is 39.4°C and this provides the warmth; she sits on the eggs most of the time,
except for short periods when she feeds, defecates and exercises
turning the eggs: essential to prevent the yolk sticking to the shell and causing
abnormalities or death of the embryo; the hen uses her beak and body to turn the eggs,
usually at 10-minute intervals
position of the embryo: despite the angle at which an egg lies, the embryo usually rises to
the top and is close to the warm body of the hen. The incubation period lasts for 21 days,
after which the chicks emerge.
Artificial incubation
Artificial incubation is a scientific method of producing small or large numbers of chicks in
batches for the farming community. It requires fertile eggs and specialised equipment called
incubators. In the poultry industry, the incubators may vary in size, shape and complexity, but
they all provide the right conditions for the production of chicks. Certain conditions are essential
for artificial incubation:
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incubators: must be cleaned, sanitised and prepared before the eggs are placed in them;
should be checked to see that all automatic parts and systems are working properly;
should have a reliable source of power (gas, oil, electricity) for the generation of heat;
must provide adequate space for each egg and chick that emerges (25 cm' per egg/chick)
fertile eggs: usually large with an average weight of 55 g; must be checked for cracks and
abnormalities; are wiped clean using a soft, damp cloth containing a mild disinfectant;
then they are placed in the incubating tray with the large ends on top
heat supply: powered by gas, oil or electricity; temperature controlled by a thermostat;
initial temperature maintained at 38.5°C for weeks 1 and 2; temperature is increased to
39.5°C in week 3
humidity: maintained around 60% to stop rapid loss of moisture by evaporation through
the porous shells of the eggs; ensures normal embryo development and reduces mortality
ventilation: well-ventilated for exchange of gases through the porous eggshell; oxygen is
needed, and carbon dioxide must be removed
turning the eggs prevents yolks from sticking to the shells; may be done manually in
small, box-type incubators; mechanical turning is achieved by automatic devices which
constantly tilt the trays.
Candling
Candling is the process by which eggs are tested for fertility by shining a light through them. It
gets its name from when candles were used as the light source. The process is carried out
between days 9-15 of incubation on eggs which are being incubated artificially so that infertile
and bad eggs can be removed.
If eggs are fertile, the developing embryo will show up as a dark spot with spider-like veins.
Infertile eggs will be clear except for the shadow of the yolk. Spoilt eggs which contain dead
embryos, show dark spots caused by bacteria. If these are left in the incubator, they produce the
gas hydrogen sulphide and will eventually explode, damaging other eggs.
100.
state the benefits of embryo transfer
Embryo transfer is the technique of removing embryos from the reproductive tract of a donor
female animal and implanting them into the reproductive tract of another female animal (the
surrogate). The technique has been developed over the last 30 years and enables animal breeders
to select female animals with desirable characteristics, use their eggs to produce embryos which
carry the desired genes, and implant the embryos into surrogate mothers. Embryo transfer is
commonly used in cattle.
Embryo transfer in cattle
Usually, the donor cow will not carry the embryos through pregnancy, so she is injected with
hormones that cause her to release more eggs than normal (super ovulate). She is then artificially
inseminated, and the resulting embryos are allowed to develop for 6 to 8 days, by which time
they will have entered the uterus. A catheter is inserted, under local anaesthetic, through the
vagina into the uterus. The uterus is flushed out with a fluid and about five embryos are
collected. This non-surgical process can be repeated six times a year. If embryos are removed
earlier, before they have reached the uterus, they have to be removed surgically from the oviduct.
After embryos have been removed, their sex is determined: female embryos are selected for use
in dairy breeds and males in beef breeds. They are then transferred into surrogate cows, which
are at the same stage of their oestrous cycle as the donor cow. This ensures that the embryo is
provided with the right environment for implantation and further development. If necessary, the
oestrous cycle of the surrogate can be synchronised with that of the donor by using hormones.
As an alternative to the transfer of embryos, eggs can be collected from the donor and cultured
for 5 days in a laboratory. They are fertilised with sperm in the laboratory (in vitro) and cultured
for a further 5 days before being transferred to the surrogate cows.
The transfer of embryos into surrogate cows can be done surgically or non-surgically. In the
surgical method, a fine pipette is used to insert the embryo into the uterus through a small hole
made by a needle. The non-surgical method involves placing a catheter into the uterus via the
vagina. The success rate of the surgical method is higher.
The benefits of embryo transfer
Embryo transfer benefits the production of livestock in the following ways:
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improvements to the herd: desirable characteristics can be introduced fairly rapidly; it is
easier to combine selected characteristics in males with selected characteristics in females
sex determination of the embryos before implantation: this results in embryos of the
required sex being used, i.e., females for dairy herds and males for beef herds (saves time
and money in building up a herd)
cheaper than importing an animal: the costs of embryo transfer are less than those
involved in buying a pedigree animal
reduces the transmission of diseases: the eggs and embryos used are examined for
abnormalities and diseases
makes use of non-pedigree females as surrogates: animals having difficulty with breeding
and non-pedigree females can be used as surrogates and produce young for the benefit of
the herd.
Embryo transfer can produce animals that are genetically identical, called clones. It is possible to
remove unfertilised eggs from a cow and suck out the nuclei using a fine pipette. Genetic
material from a young embryo with desired characteristics can be placed in the empty egg cell.
The cell is then stimulated to divide and implanted into surrogate mothers. The resulting calves
will be genetically identical.
The most famous example of a cloned animal was 'Dolly the sheep', the first mammal to be
cloned from an adult cell. A cell from the mammary gland of an adult ewe was introduced into an
unfertilised egg cell that had its nucleus removed. The resulting cell was stimulated to divide.
The embryo produced was implanted into a surrogate mother where it developed into a lamb.
101.
explain genetic engineering in livestock production
A genetically modified organism (GMO) is an organism whose genes have been altered by
genetic engineering. A transgenic organism contains genes that have been transferred into it from
another species. This technology has been used successfully in plant breeding and it has the
potential to improve productivity in farm animals. Producing genetically modified animals
involves the transfer of a gene from another organism into the genotype of the recipient animal.
This means that the characteristic that is controlled by the gene will show in the recipient.
Methods of gene transfer
Two methods of gene transfer are described below. See Figure 18.23 for details of the techniques
involved.
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Direct injection into the nucleus of a fertilised ovum: the desired gene is isolated and
injected using a very fine pipette; the fertilised ovum develops into an embryo which can
be implanted into a surrogate mother to produce an offspring; the offspring will be
transgenic if the gene has been transferred successfully.
Using viruses: the selected gene is first inserted into a virus; embryos at the 4-8 cell stage
are then infected with the virus; the virus infects the embryo, and the selected gene is
added to the DNA of the embryo's cells; embryos are then implanted into surrogate
mothers where they develop into offspring.
Examples of GMOs
Genetically modified zebra fish, called GloFish, show red, green or orange fluorescence. These
were developed to monitor water pollution. The fluorescence is caused by a gene originally
isolated from jellyfish. The GloFish have been marketed and sold as pets in the USA. In another
experiment, the human gene for lactoferrin (a protein with anti-microbial properties found in
milk) was inserted into a male embryo. This embryo developed into a calf and eventually into a
bull named Herman. When Herman was mature, a breeding programme was set up and he was
allowed to mate. All calves produced by Herman carried the human lactoferrin gene. After this
experiment, Herman was not allowed to mate again and was eventually slaughtered as he
suffered from osteoarthritis. At the time of this experiment, there were concerns raised about the
transfer of human genes in this way.
Benefits of genetic engineering
The benefits to food production worldwide could be immense as the technology improves. With
testing and controlled use, there could be significant improvements in the quantity and the
quality of food produced. The need to use excessive amounts of pesticides would also be reduced
if crops had genes for disease resistance bred into them.
Animal Husbandry
102.
describe the management practices associated with the care of baby chicks and
baby rabbits (kittens)
In nature, female animals usually take care of their young until they are old enough to fend for
themselves. However, in livestock farming farmers take care of the young animals, using
recommended farming practices. This is carried out for increased production and greater profits.
Some management practices are common to all farm animals, e.g., housing, feeding, cleanliness
and disease prevention. Other practices are specific to the young of particular animals.
Brooding in poultry
Brooding involves taking care of day-old chicks for 2 to 3 weeks. It takes place in an enclosed
area where they are housed, protected, fed and kept warm. There are two forms of brooding:
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natural brooding requiring a broody hen
artificial brooding requiring a brooder.
Natural brooding
In natural brooding, the hen incubates a clutch of eggs and produces a brood of chicks. She
provides protection and warmth for the newly hatched chicks, keeping them under her wings and
feathered body until they develop feathers and are able to withstand colder weather conditions. If
the area around the poultry house is securely fenced, the hen may roam freely with her chicks.
Alternatively, she may be confined to a coop, which protects her and the chicks from rain, hot
sun, draughts and predators, such as rats, mongooses and stray cats. The farmer ensures that both
hen and chicks have sufficient feed and water at all times.
Artificial brooding
In artificial brooding, the day-old chicks are housed in a specially prepared area, usually a corner
of the poultry house, where they are protected, kept warm and provided with litter, feed and
water. Before using a brooder, preparations should be made:
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the entire poultry pen should be cleaned and disinfected 2 to 3 days before the chicks
arrive
the area needed for the brooder is calculated by allowing 225 cm2 per chick (15 cm x 15
cm)
the area is separated from the rest of the poultry pen with a movable partition
the outer walls are screened with feed bags to keep out cold draughts of air
litter (bagasse, wood shavings, straw) is put on the concrete floor to a thickness of 5 to 7
cm; this absorbs droppings and keeps chicks off the cold ground
lighting and heating are set up over the centre of the brooding area: use a 141 infra-red
bulb or a 150-watt light bulb, together with a concave reflector to direct heat and light
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down to the floor; heat keeps the chicks warm and the light encourages feeding so that
chicks gain weight rapidly
sheets of newspaper are spread over the litter for the introduction of feed to the chicks on
day 1 and day 2 of brooding
two mini-waterers and two mini-feeders (trays) are put at opposite ends of the brooder
within the lighted area
a clipboard with a record sheet attached is placed at the entrance for poultry recordkeeping
a footbath containing disinfectant is placed at the entrance: anyone entering the poultry
pen should disinfect their footwear to prevent infection with disease-causing organisms.
The brooding process begins when chicks are placed in the brooder and ends when they are
sufficiently feathered to cope with weather conditions. During this time, the chicks are checked
on a regular basis.
After brooding, they may be placed in other poultry pens, or the movable partitions can be
shifted to allow access to more space (about 900 cm' per chick) in the poultry house.
Management practices are summarised in Table 19.1.
Chicks destined to become layers are debeaked to prevent them causing damage to other
members of the flock. In debeaking, a third of the top beak of each bird is removed with a hot
iron (a debeaker). This part is burned off and the beak is cauterised.
Brooding in rabbits
In rabbits, the act of giving birth is called kindling. A nest box containing dried grass is placed in
the hutch of the pregnant doe and she lines it with fur pulled from her own body. The doe is
allowed to give birth peacefully and suckle her young. The young rabbits, called kittens, are born
naked (hairless) with their eyes closed (blind). The litter size may vary from 3 to 10.
Management practices are summarised in Table 19.2.
The kittens leave the nest box after 3 weeks and begin nibbling solid food (herbage and starter
ration) 2-3 weeks later. Weaning takes place at 6-8 weeks when the doe is removed to another
hutch.
103.
explain the management practices associated with rearing broilers, layers and
rabbits
There are good reasons for the management practices used in rearing livestock. The provision of
suitable housing protects animals from predators and unfavourable weather. By rearing the
young in enclosed areas, they can be provided with the light and temperature conditions which
promote growth. In the artificial incubation of chicks, light conditions encourage feeding and the
temperature is adjusted to the stage of growth reached. The rate of growth is reduced if the
temperature is too low. Large numbers of healthy chicks can be produced for the poultry
industry.
Rearing rabbits
The cleanliness of housing and equipment ensures that risks of infection are reduced, and
diseases are prevented. Droppings are removed and feeding equipment is kept clean. Feed and
water left too long can become contaminated and this might cause infections that spread rapidly.
It is not necessary to provide feed and water for very young rabbits as they suckle until they are 6
weeks old, but the does need clean food and water every day for making milk to feed the young.
Adult rabbits are fed on wilted herbage and concentrates. They are excellent converters of feed
and can attain 1.8 kg in 8 weeks, with a feed conversion ratio (FCR) of 3.5:1. The young are
provided with herbage and concentrates just before and after weaning.
Rearing poultry
The provision of suitable feed at different stages of growth ensures that the young gain weight
rapidly. Young chicks are fed on starter ration until they are 6 weeks old. If they are being reared
for egg production, this is changed to grower ration until they are 15 weeks old. Laying ration, or
egg ration, is fed to them for the rest of their productive life. Broilers are given finisher ration
from 7 weeks until they are culled at 9 weeks. These rations are designed for maximum
productivity. Cannibalism occurs amongst chickens. Members of a flock peck each other,
causing bleeding and loss of flesh. If severe, it may result in death. To avoid this problem, chicks
are debeaked. The problem can be reduced by hanging small bundles of fresh herbage (grass) in
the pens of laying birds. This practice has the added advantage that the hens produce eggs with
orange-coloured yolks.
104.
rear a batch of 100 broilers per term
You will need to consider the following:
•
•
•
•
•
•
•
•
•
•
•
location of housing for the poultry
the size of housing, based on the numbers of chicks to be reared as broilers
house construction: materials needed and their source; provision of water, heating and
lighting
equipment required: feeders, waterers, cleaning equipment
feed: the type needed; quantity required; storage facilities for the feed
the chicks: source of day-old chicks
immunisation, if it has not been carried out already
record-keeping
maintenance: organisation of checking, feeding and cleaning
marketing the broilers at 9 weeks
costs: a balance sheet of the inputs and the income.
There may already be a poultry pen available, but you must clean and disinfect it and any
equipment before use. Careful records of all costs will need to be kept: the cost of feed, heating
and lighting, the chicks, any medication needed, and transport costs in obtaining the chicks or
marketing the broilers.
105.
describe the general signs of illness in farm animals
Healthy animals
Healthy animals have the following characteristics:
•
alert and responsive to environmental stimuli
•
•
•
•
•
•
•
•
the eyes are bright with no mucus on the sides or eyelids
the coat is smooth, with a sheen; the skin is soft and pliable
the appetite is good, and the ration is eaten readily
produce relatively firm faeces without straining
the urine is not bloody or discoloured green
bleat, grunt or moo normally and do not sound distressed
do not limp when walking • mix with the flock or herd and are not isolated
have a normal rectal temperature for its class: poultry 41°C, goats and sheep 39.4°C, pigs
39.2°C, cattle 38.6°C.
Signs of illness
The general signs of illness in farm animals are:
•
•
•
•
•
•
•
•
•
•
•
•
a dull, ruffled coat
swellings or lesions on the skin
dull, watery eyes with mucus on the sides and the eyelids
listlessness and loss of appetite
discoloured urine: reddish or greenish
constipation or scouring (smelly, watery faeces)
walks slowly, with discomfort, or lies down for long periods, lacking the energy to stand
up
isolation from the flock or herd, being unable to keep up when grazing or walking
high rectal temperature, indicating a fever
coughing, sneezing, noisy breathing sounds
shivering or groaning with pain
lack of alertness and failure to respond quickly to environmental stimuli.
In poultry, signs of ill-health include:
•
•
•
loss of appetite
respiratory problems
general dullness and droopiness.
106.
identify pests and diseases of poultry and rabbits
107.
describe the symptoms of pests and diseases infestation in poultry and rabbits
108.
determine the prevention, control and cure of pests and diseases in poultry and
rabbits
Poultry
The major diseases of poultry (see Table 19.3) are Newcastle, fowl pox, Marek's, coccidiosis,
and pullorum. There is also concern about bird flu.
Rabbits
The major diseases (see Table 19.4) are snuffles, coccidiosis, mange, bloat and sore hocks, but of
these only the first three are of economic importance.
Sore hocks usually occur in rabbits kept in cages with wire floors. The sores that develop on the
feet and foot pads affect the general condition but cause few deaths. Affected animals should be
moved to hutches with solid floors and sores treated with antibiotic ointment.
The cause of bloat is not known, but rabbits show a loss of appetite, a drop in weight and
diarrhoea. Treatment with antibiotics seems to improve the condition.
109.
explain the economic importance of bees
In many parts of the world (North America, China and Australasia) beekeeping is a developed
industry, involving the rearing of large colonies of bees. Beekeeping, or apiculture as it is called,
is a useful form of agriculture in developing countries. It is not expensive or difficult to set up
and hives can be constructed of local materials, as described in Chapter 17. In addition to making
honey, bees are pollinators of crop plants. In commercial apple production, many varieties are
self-sterile and require cross-pollination to produce a crop. Pollination is brought about by bees
transferring pollen from the flowers of one variety to the stigmas of flowers of a different variety
as they visit the flowers to collect nectar. The production of fruit crops, such as citrus, avocados,
guavas and mangoes, depends on pollination by bees. Seed production in vegetable crops also
relies on bees as pollinators. The production of honey provides income for small farmers. Hives
can be positioned in vegetable plots, orchards and on the borders of fields. Honey is an easily
digested food and was used as a sweetener in cooking before the extraction of sugar from sugar
cane. It also treats wounds and infections of the eyes and skin. It reduces inflammation and acts
as a disinfectant.
110.
differentiate among the types of bees in a hive
In a honeybee colony, there are three types, or castes, of bee (see Table 19.5). Each type is
adapted to performing specific functions within the colony. The three types are:
•
•
•
the queens: fertile female bees; mate with drones (males); lay many eggs which develop
into new individuals; fertilised eggs develop into female bees and unfertilised eggs
develop into drones
the workers: sterile (unfertile)female bees; carry out the duties around the hive; act as
nurses for developing bees; clean the hive; collect nectar and pollen
the drones: fertile male bees; mate with the queen.
A bee colony consists of one queen, up to 50 000 workers and a few hundred drones.
111.
describe the social activities of bees
The queen
The queen is responsible for laying eggs. After she has been fertilised by drones on her nuptial
flight, she can lay about 2000 eggs a day. Eggs are laid singly into hexagonal (6-sided) wax cells
on the combs in the brood box of a hive. Most eggs develop into workers, some into drones and
very few are destined to be queens. The cells in which new queens are reared are bigger than the
others and the larvae are fed only on royal jelly, a nutritious substance rich in protein which is
produced by the workers. New queens are only produced if the colony has become large and
swarming is about to take place, or if the old queen dies. When swarming occurs, the queen and
many workers leave the colony and build a new nest somewhere else. This leaves the previous
colony without a queen, until a new one hatches from a queen cell. When the new queen
emerges, she will go on a nuptial flight, mate with several drones and begin laying eggs.
Commercial beekeepers try to prevent swarming by making sure that there is only one queen per
hive.
The drones
The drones cannot carry out many activities in the colony as they have reduced mouthparts, so
they cannot collect honey or make cells. Their main purpose is to mate with the queen. After
mating, the drones will die. If food becomes scarce, drones are driven out of a hive by the
workers.
The workers
The workers carry out many activities within the hive and also forage for honey and pollen
outside the hive. When they first hatch, young workers clean out cells and feed older larvae on
pollen and honey. As they get older, they secrete brood food, the royal jelly, on which the young
larvae and queen larvae are fed. Their movements keep the hive warm.
When workers are 2 weeks old, their wax glands become active, and they make wax for the
construction of new cells on the comb and for repairs to older cells. These young workers collect
nectar and pollen from the foraging worker bees and store it. They convert nectar into honey by
reducing the water content.
After 3 weeks, workers become foragers and leave the hive in search of nectar. These forager
worker bees are able to communicate the location of sources of nectar to other foraging bees by
performing special 'dances' to show the direction and distance of the source from the hive. In
addition to nectar, foraging bees also collect pollen, water and propolis (a sticky substance
collected from tree buds which is used to seal cracks in the hive).
The social organisation of the colony is controlled by chemicals secreted by the queen, called
pheromones. These get passed from the queen to the workers and control their behaviour.
112.
identify the causes, symptoms, prevention, control and cure of pests and diseases
infestation in bees
The main diseases of bees are:
•
•
•
•
foulbrood: caused by a spore-forming bacterium
acarine mite infestation
dysentery
varroasis: infestation by the parasitic mite Varroa.
These diseases are not widespread in the Caribbean. Therefore, beekeepers in the region must
take great care to keep their bees free from disease.
American foulbrood
American foulbrood is a highly infectious disease caused by the bacterium Bacillus larvae. If
bacterial spores get into young larvae, they germinate rapidly and kill the larvae. The bacterium
does not affect adult bees or older larvae. Spores are very resistant to heat, cold and disinfectants.
They remain viable for years in old combs, in honey and on equipment. The larvae die within the
capped (sealed) cells of the comb, which first become slimy, then dry out and turn dark brown.
These cells produce a foul smell, which gives the disease its name. The disease can be detected
by inspecting combs of the brood box for any discoloured or brown cells. The condition can be
treated with antibiotics which are added to the hive; but this does not kill the spores, it only
delays their growth. The infection is spread by:
•
•
•
feeding infected honey to young larvae
use of second-hand equipment
combs being moved from an infected hive to an uninfected one.
The best preventive measures are strict cleanliness, regular inspection of the brood in the hives
and sterilisation of all equipment. Clothing should be thoroughly washed in hot, soapy water.
Acarine mites
Acarine mites are tiny arthropods (related to spiders) that get into the breathing tubes of adult
bees. The mites get into the young adult bees in the first week after hatching, before they have
left the hive, so the spread of the infestation depends on the young bees being in contact with
older, infested bees. Mites get into a colony on the bodies of the workers or from a colony being
moved into an infested hive. The affected bees have distended abdomens and their wings take on
a different shape, causing them to flutter. As the life of a worker is short, infestations are usually
not serious and do not affect honey production. During poor weather, when bees are confined to
the hive for longer periods, infestations may become more serious and need treatment. Treatment
involves a smoke strip, which is lighted and allowed to hang down so that smoke circulates
quickly around the hive. The bees are prevented from leaving the hive while the smoke
circulates. This smoke is toxic to mites, but harmless to the bees, the brood and the stores of
honey and pollen.
Dysentery
Dysentery is suspected when the hive contents are soiled by the faeces of the bees. This
condition occurs mainly in countries where bees have a quiet period during the winter and are
confined to the hive. A build-up of faeces in the hive may be caused by too much water in the
food. Bees should only be fed refined beet sugar or refined cane sugar: brown sugar or raw sugar
causes excess water and the possibility of dysentery. The condition is not serious in itself, but it
can aggravate other infections.
Varroasis
Varroasis is caused by an infestation of larvae and adult bees by the parasitic mite, Varroa. These
mites feed on the body fluids of bees and can be seen as small brown spots on the bee's thorax.
The mites carry a virus which results in deformed wings in adult bees. Severe infestations result
in the death of whole colonies and beekeepers need to inspect hives regularly for signs of the
mites. Mites may be present in sealed brood cells. Mites can spread when components of a hive
are interchanged during management of the colony. Movement of hives and queen bees also
spreads an infestation. Infested apiaries should be isolated. Affected bees, combs and other
components of a hive should be destroyed. If the disease becomes widespread, chemical controls
that kill mites can be applied in the form of aerosol sprays. Tobacco smoke also works. These
treatments are expensive and may leave residues in the honey.
113.
describe the harvesting of honey and other bee products
Honey
Honey is stored in the cells of the combs on the supers in a hive. When honey is the right
consistency, bees cap the cells with wax. Any uncapped cells are likely to contain 'unripe' honey.
The best way of removing honey is by using a machine called a spinner. These are expensive, but
it is possible to hire one or join with other beekeepers for a 'honey-spinning' session using a
communal machine. The procedure involves the following steps:
•
•
•
•
•
•
thorough cleaning of the spinner with boiling water
drying the spinner
removal of the wax capping of the cells on both sides of the comb: this is done by
running a sharp knife over the surface; wax is scraped on to a tray; if it is heated, residual
honey can be separated from the wax; the wax can be saved and used later
place uncapped frames into the spinner: most spinners will take up to four frames
extract the honey: start the spinner slowly, gradually working up to full speed; after 2
minutes, reverse the frames and repeat the spinning; it takes 5 minutes for the honey to be
removed from the frames
remove frames from the spinner: there will still be some honey left in the frames, but they
can be replaced in the super and returned to the hive; the bees will clean the frames.
As an alternative to using a spinner, honey can be removed from a comb by simply scraping it
off with a spoon. Using this method, the honey will be mixed with pollen, wax and bits of dead
bees. Pieces of comb can be cut out and sold as 'comb honey', but this will also have pollen in it.
After honey has been extracted it will need bottling. If a clear honey is desired it must be filtered,
either through damp muslin or using stainless steel filters. The filtered honey is poured into
clean, dry jars and the lids screwed on. If the honey is to be sold commercially, there are
regulations about extracting and labelling it. Extractors must be made of plastic or stainless steel
and labels need to state the name of the producer and weight of honey.
Beeswax
Beeswax is secreted from wax glands on the underside of the abdomen on a worker bee. The wax
is used to construct cells in which eggs are laid and for storage of honey and pollen. Beekeepers
can collect wax from the combs when honey is extracted, but it has to be cleaned before use.
There are various methods of extraction, but the simplest is to put the wax on a metal grid over a
tray, cover it with a transparent lid and leave it in a sunny place. As the temperature rises, the
wax will melt and can be filtered and allowed to drip into a container. This procedure should be
watched; if the temperature gets too high the wax could burn. There are many uses of beeswax:
•
•
•
•
•
•
making candles
cosmetics
crayons
paints and varnishes
coatings for washable wallpaper
floor polish and car wax.
Medicinal products
Honey has been used to treat infections and reduce inflammation, but other products from
beehives also have medicinal properties. Not all the claims made for these are true, but they are
used as 'natural' remedies and do work for some people. None of the products will harm. Propolis
is the sticky substance used by bees to seal cracks, line the hive and cells and mend the combs. It
is collected from the bark and buds of trees.
Propolis can be removed from hives by scraping. It has been used as an antiseptic and is now
marketed as an ointment, as lozenges and in capsules. It is said to help throat infections, the
common cold, mouth problems, some skin conditions and stomach ulcers.
Pollen contains carbohydrates, proteins, vitamins and minerals. It is used by bees to make brood
food on which larvae and young bees are fed. It can be collected by fitting to the hive entrance a
device which scrapes pollen from the legs of bees.
Various claims have been made for the benefits of taking pollen, but it has been used to protect
against hay fever. Royal jelly is the milky liquid which worker bees make and feed to the young
larvae. All young larvae are fed on this for a few days; after this time only, those larvae destined
to be future queens are fed on it. Jelly is collected from queen cells by removing larvae and
scooping out the contents. Commercial production involves rearing many queen larvae as only
about 25 g can be collected from 100 queen cells. It is very expensive.
Animal Products Technology
114.
offal
list principal farm animal products and by-products including those derived from
Most products from farm animals are used for human nutrition, but some are processed and used
for livestock feed. In addition, a number of by-products have important economic uses.
Eggs
Eggs are used in many ways and are produced worldwide in very large quantities. They are
highly nutritious and contain proteins, fats, vitamins and minerals. In the Caribbean, both
hatching eggs and table eggs are produced from layers, raised intensively on farms or in open
areas (free range) in rural communities. Table eggs (for eating) are of two types:
•
•
farm eggs or farm-fresh eggs: these have pale yellow yolks and are usually cheaper
common fowl eggs: these have orange yolks, are popular and more expensive.
Hatching eggs are used by poultry farmers. Either these eggs are incubated and then sold as dayold chicks to be raised as layers or broilers, or poultry farmers will purchase fertile eggs to
incubate, raise the chicks and replenish their stock. By-products from eggs include:
•
•
dried egg: this can be whole dried egg, dried egg yolk or dried egg white; dried egg can
be reconstituted with water and used in cooking
eggshells: composed of 95% calcium carbonate; can be ground to a powder and used in
animal feed as a source of calcium; artistic uses include painting.
Milk
Milk is important in human nutrition and much milk is consumed in its fresh form. However,
milk is perishable and requires special treatment so that its freshness, flavour and taste are
maintained. The major processes involved in milk treatment are:
•
•
•
•
•
examination: to determine bacterial content, butterfat content, unusual odours and foreign
matter; examination is important for grading milk
removal of foreign matter, such as dirt particles: this is done using a machine called a
clarifier, by centrifugal force
separation of butterfat produces low-fat and skimmed milk; other low-fat products can be
made using the milk
homogenisation: butterfat globules are broken up into minute particles; milk is heated to
72°C for 15 to 20 seconds to pasteurise it; then it is subjected to high pressure and forced
through a valve; cream formation on the surface is prevented
pasteurisation: destroys pathogenic organisms, thus safeguarding public health; prolongs
the storage of milk; maintains the nutritional value, taste and colour; achieved by heating
•
•
to 63°C for 30 minutes or to 72°C for 15 to 20 seconds; milk is then rapidly cooled to
about 3°C
sterilisation: used in production of UHT (ultra-high temperature) milk; milk is heated to
140°C for 3 to 5 seconds; this destroys all micro-organisms; taste, colour and nutritional
value are maintained; this considerably extends the storage life of milk
packaging: glass bottles, paper cartons or tetrapacks can be used; these are sealed
automatically and aseptically; they are placed in boxes and stored at cool temperatures.
Packaged milk should be stored in a cool place at 4°C. Milk is transported in refrigerated
delivery trucks to supermarkets and consumer outlets. Milk is used to make other dairy products
either on the farm or in processing plants. Those made on the farm include butter, cottage cheese,
ghee, yoghurt or dahee and ice cream. In addition, powdered and condensed milk (sweet milk),
butter, cheese and ghee are made in processing plants.
Honey
Honey and other products from bees have been described in Chapter 19.
Fish
Fish and shellfish are of importance as food for humans. They are rich sources of protein,
vitamins (A, D, B vitamins — thiamine, riboflavin, and niacin) and minerals (iodine, calcium
and phosphorus). Fish provides an alternative to meat and is more easily digested than many
forms of meat. It can be used in a variety of ways, including freshly cooked, baked, curried,
stewed, fried, grilled, and steamed. Some fish and shellfish, such as sushi and oysters, are eaten
raw. Fish can be preserved by freezing, smoking, salting, drying, and canning.
Fish is also used as a feed supplement for livestock. The bones of fish are ground up and made
into bone meal. Fishmeal is made by drying and grinding fish waste or unwanted fish. Ground
oyster shells are fed to laying hens, providing calcium for shell formation.
Meat
Meat is an important source of protein in the diet. We eat meat from:
•
•
•
•
•
•
poultry: chicken and duck
goats
sheep: mutton and lamb
pigs: pork and bacon
cattle: beef
rabbits.
Meat production can be affected by climatic and environmental conditions, public health and
safety concerns, praedial larceny and religious beliefs. There is an increasing demand for meat
and meat products that are:
•
•
fresh from the farm
lean and muscular, with little fat
•
organically produced (home-grown animals): these are reared without growth stimulants
or chemicals in their feed.
The carcass of a slaughtered animal is usually treated to produce a dressed carcass (the entrails
and head are removed).
The dressed carcasses of farm animals are usually cut into sections, each having a special name.
The cuts have varying shapes, and are differently graded for specific purposes, such as roasting,
grilling, braising or for the barbeque. They are graded and priced to suit the tastes, preferences
and affordability of consumers. The major meat cuts are illustrated in Figures 20.3-20.6.
The carcass quality refers to these characteristics of the carcass:
•
•
•
•
•
its conformation: proportion of meat and fat to bone; meatiness; shape
colour: beef should be bright red; veal is white or light pink; pork is greyish-pink or
darker; lamb is light to dark pink; chicken is pinkish white; duck is reddish white
texture: whether it is soft, moist and firm rather than tough, stringy and dry
fat: quantity; colour (firm and white in pork; white, smooth and even in lamb; creamy
white in beef; whitish yellow in poultry); marbling (fat between and around the muscle
fibres)
palatability: aroma; tenderness; juiciness; flavour.
Apart from the major cuts described above, other fresh products for human consumption include
steaks (beef), minced meat (beef, pork, lamb), sausages (beef, pork), chops (lamb, pork) and
roasts (beef, pork, lamb). Meat products include ham and bacon (cured meats from pigs),
together with smoked sausages, such as bologna and salami.
Offal and other by-products
Offal refers to those parts of an animal that are used as food but do not consist of skeletal muscle,
or meat. It is a term used to describe the internal organs of an animal and includes liver, kidneys,
casings of the intestines, tongue and trotters. Many nutritious dishes can be made using these.
For example, black pudding is made from blood, tripe is prepared from part of a cow's stomach,
and many dishes contain chicken livers. Offal and meat scraps are made into pet food.
Other parts of farm animals can be put to good use. The skins are made into leather, bones into
bone meal and hoofs and horns into fertiliser. Fat is rendered down and used to make lard and
soap.
Biogas
Biogas can be generated using animal manure. The manure is collected and placed in a large
fermentation tank with water. Anaerobic bacteria (bacteria which do not need oxygen) break
down organic matter releasing methane and carbon dioxide gases. These gases can be stored and
used as a fuel. In some parts of the world, farmers generate fuel for heating and cooking in this
way, as an alternative to using firewood.
115.
determine the dressing percentage of different farm animals
Live weight is the weight of an animal before slaughter. Live weight in cattle and small
ruminants is often referred to as 'on the hoof'. Dressed weight, also known as dressed carcass
weight or slaughter weight, is the weight of the meat after the animal has been slaughtered and
offal has been removed.
Live weight and carcass weight are directly related to the dressing percentage of the slaughtered
animal. These weights vary considerably among the different classes of farm animals and are of
economic importance to producers and consumers.
Dressing percentage (see Table 20.1) refers to the percentage of the live weight usually obtained
as edible carcass (meat) after slaughter. The formula for calculating the dressing percentage is as
follows:
Relationship between weight and age
The relationship between weight and age in farm animals helps the farmer to decide on the right
time to slaughter. Some animals may be slaughtered at the age of weaning. This is the practice
for suckling pigs and calves for veal. It may be impractical to rear meat animals beyond a certain
age because:
•
feed costs for the animal increase as it gets older
•
as the animal ages, it consumes an increasing quantity of feed but puts on weight at a
much slower rate, so that the feed conversion ratio (FCR) drops significantly.
The weight to age relationship also indicates the stage of development in terms of a balance
between bone and muscle. Optimum slaughter weights are based on research data. They take into
account the breed, age, sex and feeding regimes of the various classes of farm animals.
116.
determine the most appropriate age to slaughter broilers
The time for slaughter can be determined by their dressing percentage and their age. At about 9
weeks a broiler will weigh 2 kg. This varies slightly with the breed, feeding regime, type of feed
used and environmental conditions. Broiler chicks are fed on starter ration until 6 weeks old and
given finisher ration for the next few weeks. Broilers have a dressing percentage between 75 and
80%. The farmer can work out the best live weight that will give a profitable return on the
investment in feed and decide when to send the broilers to market. Broilers are usually sent
around 9 weeks old, but faster-growing breeds may reach the required weight earlier, at 7 weeks.
If the number of broilers is small, they can be slaughtered by hand. However, with larger
numbers slaughtering is usually mechanised and a production line is set up. Whichever method is
used, birds are not given food for 6 to 8 hours but are allowed water.
Using humane methods
The most humane method is to cut the jugular vein in the neck with a very sharp knife. Blood
drains out for 2 minutes and the bird is then scalded and plucked to remove feathers. If carried
out at home, the bird is caught and held firmly with its head pointing downwards. It will lose
consciousness quickly once the vein has been cut. Scalding can be carried out by immersing the
bird in a bucket of hot water (60°C) for 1 minute. This makes the feathers easier to remove and
feathers should be taken off immediately after scalding. On large poultry farms, birds are
suspended, head downwards, from hooks on a moving line. They are stunned electrically before
their necks are cut, either manually or mechanically.
Dressing and packaging
The carcasses are dressed by removing all internal organs, the head, neck and feet. After removal
of the head and neck, internal organs in the upper part of the body cavity can be loosened.
A cut is made all round the vent to remove the intestine and other internal organs. A hand can be
inserted into the cavity and the organs are loosened and pulled through the vent opening. The
bird is washed thoroughly and then cooled.
The heart, liver and gizzard (stomach) are separated from the rest of the intestines and cleaned.
The heart is washed to remove any blood, the gall bladder is removed from the liver, and the
gizzard is opened to remove any contents and its lining removed. These parts are referred to as
the giblets and are often sold with the bird. Chicken livers are used to make pate (pie) and other
dishes. Whole birds are packed into polythene bags and sent for sale or frozen.
117.
explain the process involved in the marketing of eggs and meat
Eggs
Eggs are fragile so care needs to be taken when handling them. Firstly, eggs are collected from
nest boxes and battery cages by lifting each egg carefully and placing it in an egg basket. Care
should be taken to prevent eggs from rolling, colliding and cracking. The number collected is
recorded each day.
Eggs are then cleaned by wiping with a clean piece of cloth which has been moistened in clean
water and squeezed to remove the excess. All blemishes and bloodstains should be removed. It is
not advisable to immerse eggs in water because washing removes the cuticle, opening up pores
in the shell. This allows the entry of bacteria and the loss of water through evaporation.
Grading is done according to colour, size, weight, and injury. Eggs can be brown-shelled or
white-shelled, jumbo, extra-large, large, medium, small and cracked. Grading is necessary for
quality control, consumer satisfaction and pricing. Graded eggs are packed into egg crates,
holding 6, 12 or 30 eggs. Each egg is placed in the crate so that the larger end is always at the
top. This avoids putting pressure on the thin membrane and the air space at the larger end. Crates
are stored in a cool, clean room, free from unpleasant odours. The temperature should be 10 to
13°C.
Eggs are supplied wholesale to supermarkets and middlemen for pricing, labelling and retailing
to consumers.
Meat
The marketing of meat follows slaughter of animals at the appropriate age or weight. Slaughter
of sheep, goats, pigs and cattle is usually carried out in an abattoir or slaughterhouse. Local laws
ensure that the facilities are hygienic and humane and that animals do not suffer undue distress.
The animals are handled gently, provided with fresh water, and transported in suitable vehicles.
After slaughter, each carcass is bled, the hides removed, and the internal organs taken out. The
carcasses are then chilled. Meat is inspected at the abattoir and stamped as fit for human
consumption or taken away for disposal by burial or burning.
Meat is not cooked and eaten immediately after slaughter but has a period of 'conditioning' or
'ageing' during which time it develops flavour as the muscles become tender. After ageing, the
carcasses are cut into the joints and cuts described on page 303.
Meat is marketed in different forms: it can be bought straight from a retailer as a large joint, or it
may be processed further into chops, steaks, and mince. In many supermarkets the meat is
packaged, labelled, and priced for the convenience of the consumer.
Packaging needs to allow the passage of gases but at the same time reduce the loss of water. To
achieve this, plastic films control the atmosphere inside packs. It is possible to maintain suitable
levels of oxygen and carbon dioxide so that meat is kept fresh, and its colour remains attractive.
The red of fresh meat is maintained by the presence of some oxygen within the pack. Packaging
ensures that meat is not handled, is kept clean and is visible to the consumer. The packs are
chilled and will keep in a refrigerator for a few days after purchasing.
Vacuum packaging is now used for meat and meat products. The meat joints are placed in the
packaging and a vacuum is applied to reduce gas in the space between the meat and its
packaging. The atmosphere inside the pack will contain less oxygen, thus discouraging the
activities of aerobic bacteria which could cause spoilage.
The packaging of cured meats, such as ham and smoked sausages, does not need to be permeable
to oxygen as the pink colour is developed during the curing process.