Agriculture notes form 3
PHYSICAL FARM PLANNING
It is the demarcation of land on a farm into class capabilities as regards to its suitability to
agricultural activities.
i.e. Classes of land page 16 dynamics of agriculture O level
Factors to consider when planning
1. Land – the availability of land and how much of it is arable.
2. Labour- the availability of labour and the type of labour required for different
agricultural activities.
3. Capital – the amount of capital needed to start agricultural activities.
4. Water resources- The availability of a water source and how reliable it is.
5. Farm supplies – the location of areas to acquire farm supplies and the distance to the
location.
6. Markets- the location and availability of market for the produce is also important.
7. Budgeting- the budget is important to determine the viability of the project.
Importance of Physical farm planning.
1.
2.
3.
4.
5.
6.
It establishes a clear direction for management and employees to follow.
It defines the measurable terms of what is important for the farm.
It helps in efficient allocation of resources.
It is the basis for evaluation of management decisions and key employees.
It highlights water and access routes such as roads.
It help increase cropping and livestock rates.
CROP ROTATION
It is the practice of growing a series of different type of crops in the same area in sequential
seasons.
Advantages.
-
improves the soil structure by alternating deep rooted and shallow rooted crops
reduces the build-up of pests and diseases.
Helps to improve soil fertility by including legumes in a rotation
Helps to manage the soil PH
Soil erosion is minimised
Some of the weeds are effectively eradicated
Principles of crop rotation
-
Shallow rooted crops should be followed by deep rooted crops
Crops of the same family should not follow each other
Always include a legume
Add manure or organic matter regularly
Grow crops suited to the climatic conditions of the area
Soil type should be correct for the crop s selected
-
After heavy feeders eg cabbage plant light feeders
Four crop rotation example
Cotton---------maize------------sweet potato----------field beans
ENVIRONMENTAL FACTORS
Rainfall
Rainfall distribution
This refers to how effective rainfall is shared or spread throughout the season
Rainfall distribution determines the season quality.
Rainfall must be distributed in such a way that it is available during critical growth stages like
germination, flowering grain filling.
This critical stages require a lot of moisture.
Distribution of rainfall is measured in terms of the number of rainy pentads.
A rainy pentad is defined as the second one the three five day periods which together receive
more than 40mm and any two of which receive at least 8mm of rainfall.
Natural farming regions 1 and 2 tend to have more rainy pentads and consequently higher
crop yields than regions 3,4 and 5.
The amount of Rainfall differs seasonally from place to place.
Generally in Zimbabwe there is more rainfall in the eastern parts of the country becoming
less as one moves towards the western parts.
The areas that receive good rainfall amounts are involved in such activities as crop
production and forestry
Reliability of rainfall
This refers to the regularity of the rainfall from season to season in a farming area or region.
It also considers the regularity of the onset of the rainfall from year to year
Areas in regions 1 and 2 have more reliable rainfall than other regions
Unreliable rainfall or mid-season droughts or dry spells are experienced in natural regions 3,
4 and 5
Effectiveness of rainfall
It is the rainfall that supplies adequate soil moisture for plant growth.
Light showers are ineffective if the moisture is not enough for infiltration.
Heavy rainfall is ineffective if water is lost as surface runoff and deep percolations beyond
the reach of underground roots.
Effects of rainfall distribution and intensity on agricultural activities
Distribution
-Animals lose body condition score due to infection by internal parasites such as liver fluke
and tapeworm which breed in damp and swampy areas.
-root rot may develop under conditions of excessive rainfall.
-drought causes wilting of crops
Intensity –intense rainfall causes lodging of trees, dropping of flowers, leaves and fruits
High intensity rainfall also causes erosion and subsequently leaching and siltation
Low intensity rainfall may cause shortage of moisture if it is not enough for infiltration.
Timber harvesting, marketing and Deforestation
Methods of harvesting trees
-
Hand felling- trees should be cut 10 cm above ground using a hand axe or machine
operated saws.
Machine felling-this is done using motorised chain saws.
Trees should be cut at an angle to avoid water accumulating on the stump which may
cause rotting.
After felling trees the regrowth on stumps are called coppices
Clear cut – this is the removal of all trees in the area, no tree will be left standing
Shelter wood cut- mature trees are removed in 2-3 harvests over a period of 10-15
years. This method allows regeneration of medium to low shade towering species.
Methods of treating timber
-chemical treatment using creosote oil.
-use of used oil.
-Seasoning- this refers to drying of timber through evaporation of excess moisture either by
natural (air drying) or artificial (kiln drying) methods
-Partial drying
Possible markets for timber
-industry for paper manufacturing
- Manufacturing of furniture,
-Mining for making pillars
-wood for fuel for example households and tobacco curing.
-construction eg houses, and fencing
Causes of deforestation
-clearing land for cultivation.
-collection of wood fuel.
-Cutting down for construction of houses and roads
-Mining, particularly open cast where large tracks of land are cleared
-veld fires
-Construction of dams
-Logging- wood based industries destroy large forests
Effects of deforestation
-Soil erosion- soils are exposed resulting in washing away of topsoil.
- The water cycle is affected as evapotranspiration is reduced.
-Loss of biodiversity- there are a number of plant species wiped out and animals that depend
on the plant as habitat
-Climate change due to accumulation of carbon dioxide in the atmosphere.
-land degradation.
-Siltation of dams- accumulation of soil in water bodies.
Possible solutions of deforestation
-Re-afforestation and afforestation programmes to establish exotic and indigenous woodlots.
-Develop alternative energy sources rather than depend on wood, alternative sources may
include liquid petroleum (gas) or electricity or solar power.
-government to pass and enforce laws to preserve existing forest resources.
-Improved farming methods- this will prevent the indiscriminate cutting down of trees.
- encourage farmers to plant trees for poles and curing tobacco, instead of using wood as fuel
they can use coal instead.
Importance of afforestation and reforestation
-Trees can control runoff and soil erosion thereby reducing siltation and water loss
-Trees maintain soil organic matter
-Trees reduce soil toxicities (acidification and salinization)
- Forests utilise solar energy efficiently.
- Trees help to reclaim eroded land.
-forests play an environmental and ecological role.
-trees moderate microclimate in residential areas.
-leguminous trees fix atmospheric nitrogen
-Helps in apiculture (bee keeping).
-income for famers.
Wildlife
Indigenous knowledge systems in wildlife conservation and preservation
Definition: indigenous knowledge systems (IKS) are a body of knowledge, or bodies of
knowledge of the indigenous people of particular geographical areas that they have survived
on for a very long time.
-IKS is local knowledge that is unique to a given culture or society.
-IKS is built by societies through generations of living in close contact with nature. It
includes norms, taboos, a system of classification of natural resources, a set of empirical
observations about the local environment and a system of self-management that governs
resource use.
Use of Totems
-Amongst traditional communities such as the Ndebele and Shona where totemic is practiced,
it is taboo for clan members to kill animals which serve as the revered symbol of their
families.
-the family members whose totem is symbolised by a certain animal become custodians of
that particular animal.
Taboos and rules
-Protection of wildlife through taboos and cultural laws was very common in the
Zimbabwean culture as well as other African societies.
-sacred animal species being for example owls, snakes, pangolins, tortoises and porcupines
-It has been studied that in some Zimbabwean cultures, snakes symbolised the ancestral
beings. Consequently, it was taboo for the local people to kill them. The belief in these
symbolic snakes was a favourable factor which necessitated their annual increase in numbers.
-Although, it has been reported that taboo species may still suffer from human impact, as they
are not necessarily free from being poached by other people who doesn't value them also as
taboo species.
-Thus it has been shown that formal rules and informal law enforcement regulations are
important in influencing the behaviour of people in natural resources conservation.
-Some plants are taboo to chop down or use as firewood eg umphafa (also known as
umlahlabantu) used in burial ceremonies.
-some animals are also taboo to kill e.g swallows (inkonjane, nyenganyenga) who are
believed to signal the coming of rainfall.
Sacred areas
-The local names of these areas differ between regions (e.g., indawo ezizilayo, masango
anoera, nzvimbo dzinoera) and are usually included in areas regarded as sacred sites in
revered areas,
-local people refrain from cutting down trees, killing animals, harvesting useful plants within
such sites, or even entering or passing nearby, believing that the spirits or deities would be
offended and bring harm to the persons, families, or even whole villages if the sites are
disturbed.
-What is generally known, however, is that these areas exist in communal areas all over the
country, but are scattered, and in the form of grazing lands, watersheds and even mountains
-Matopo Hills are examples of such a place, they are of spiritual significance to the Ndebele
and Shona people. Important traditional ceremonies are conducted at shrines in these hills; for
example, during severe drought rainmaking ceremonies are often performed at the Njelele
shrine.
-It is believed that the ancestral spirits of the people live among the hills.
-In most African communities, the ancestral spirits are believed to be living in the forests and
special trees, caves and ruined homes and water bodies.
-There are studies that have been carried out that claim that certain sacred hills were places of
abode for ancestral spirits. Also, echoes of music and dance used to be heard on the following
day after Mukwerera rainmaking performances.
-The Amarula and Muhachi trees are of special mention in Matobo.
-It is equally taboo to hunt or poach animals within or running into a sacred forest because
they belong to Mwari and the ancestral spirits.
-Such landscape elements are therefore normally treated with veneration to ensure limited
human access into them lest the spirits be offended and driven away „homeless‟.
-In this regard, it is taboo to cut down trees found in a sacred place without the sanction of the
local chief priest.
-Furthermore, it was found out that the community members were culturally not allowed to
fell trees from these sanctified hills and they [hills] grew into thick forests.
-Thus the indigenous knowledge system was utilised not only to protect wild animals and
deforestation; it was a tool that intensively combated soil erosion as well.
Special meat for chiefs
Such animals as the pangolin should not be eaten by anyone except the chief, since the chiefs
are few the pangolin will be preserved
Principles of conservation and preservation and how they affect wildlife trading
-Parks and wildlife act of 123/1991 chapter 20:14 – the act seeks to guarantee that the
wildlife heritage of Zimbabwe is protected through sound management and restrictive laws
- The restrictive laws include the fact that no persons is allowed to hunt for any wild animal
without authorisation from the responsible government department and may not trade in any
of the products that are obtained from the wild animals.
-the act also provides for the establishment of national parks, botanical gardens, sanctuaries,
and safari areas where the wildlife is protected and this also restricts the trade in wildlife.
-CAMPFIRE is another programme that helps in restricting the trade in wildlife as it seeks to
benefit communities who live with the wildlife.
-non-governmental organisations such as World Wide Fund for nature (WWF) who are
involved in wildlife conservation.
-CITES is an international agreement which forbids commercial trade in endangered species
while allowing trade in species that can withstand the pressures of trade.
Effects of poaching
-Loss of biodiversity.
-Extinction.
-Imbalance in the ecosystem.
-Animals that depend on a particular species is also affected.
-Loss of foreign currency.
-Loss of income for people who depend on tourism and wildlife.
Biodiversity in relation to species, genetics and ecosystem diversity
Biodiversity- refers to a variety of plants and animals that exist in a particular natural
environment.
Species diversity-refers to the number of different species in an area
Ecosystem diversity –refers to the number of different ecosystems in an area
Genetic diversity-the sum total of genetic information contained in genes of organisms
Habitats of wild animals
-Habitats of wild animals include, water, soil, trees, rivers, dams, caves and sea.
-causes of differences in wildlife habitats include:
-Genetic makeup.
-climatic factors.
-soil factors (physical).
-competition between species.
-diets and feeding patterns.
Soil and water
Weathering
Forms of weathering
-physical weathering- this involves the breaking down of rocks due to the effects of running
water, freezing water, temperature changes and wind.
The rubbing action amongst small rocks carried in water weakens and breaks the small rocks
to form soil.
When water occupying cracks in rocks freezes, it expands, widening the cracks and when it
melts the rock contracts this is called freeze thaw action.
Rock particles peel off due to expansion due to high daytime temperatures and contraction
due to night time low temperatures.
Sand particles carried by wind hit surfaces of solid rocks and particles break further into
smaller particles.
-chemical weathering-chemical weathering changes the minerals in rocks into new weaker
substances that can be broken down.
Hydrolysis is a form of chemical weathering where the rock is weakened and broken down to
soil by the replacement of cations by hydrogen.
Carbonation is chemical weathering form where carbon dioxide dissolves in water to form a
weak carbonic acid which weakens limestone rocks.
Dissolution is a form of chemical weathering where rocks are weakened and broken down
due to dissolution and draining out of salts contained in rocks.
-Biological weathering-this is the breaking down of rocks due to actions of living organisms
on rocks.
Microbes decompose organic matter to produce weak humic acids which dissolve salts and
break the rocks.
Plant roots penetrate cracks in rocks and widen the cracks as they grow. This weakens the
rocks and breaks them down.
Soil textural classes
-soil consists of particles which vary in size namely sand, silt and clay. Each of the se
particles can be referred to as a soil fraction and the millimetre (mm) is the unit of measuring
their sizes.
Classification of soil fractions
Name of particle (Fraction)
Clay
Silt
Sand
Gravel
Diameter of soil particles (mm)
Less than 0.002
0.002 - 0.02
0.02 – 2.0
Greater than 2.0
-in practice, soils do not consist of 100% sand ,silt or clay but are mixtures of these three
components or particles.
-the percentage composition of sand, silt and clay in a soil is known as soil texture.
-in Zimbabwe eight (8) textural classes have been identified and these are given in the table
below:
Textural class
Sand
Loamy sand
Sandy loam
Sandy clay loam
Clay loam
Sandy clay
Clay
Heavy clay
Definition
Over 85% sand
75% - 85% sand
Less than 20% clay and 50% - 75% sand
20% - 35% clay, 45 – 80% sand
20 – 40% clay and less than 45% sand
Greater than 35% clay and 45 – 65% sand
Greater than 40% clay and less than 45%
sand
Greater than 50% clay. These are stiff, sticky
clays with shiny surfaces when dry.
Textural triangle
Soil structure
-soil structure refers to the arrangement of the soil particles (sand, silt and clay) into clusters
called peds or aggregates.
-soil structure may be changed by the farmer.
-soil structure may be blocky, platy, prismatic or spheroidal. The spheroidal structure is
further subdivided into 2 subclasses: crumb and single grain.
-the crumb structure is the most ideal for crop production because it has good aeration, good
drainage, can be easily worked on, allows good root penetration and has good water and
nutrient holding capacity.
Methods of improving and maintaining good structure
-application of organic manure, composts and green manure.
-cultivation of soil when not too wet or too dry
-addition of agricultural lime. Lime results in more particles combining together to form
crumbs through a process called flocculation
-include crops with high leaf litter in a crop rotation programme. The litter will eventually
decompose to humus which binds the soil into a good crumb structure.
-maintain well drained soils
-practising minimum tillage reduces destruction of soil structure by tillage equipment
Factors affecting soil structure
-excessive tillage breaks down soil structure
-use of heavy machinery in the field compacts the soil and breaks down soil structure
-working on the soil when it is too wet or too dry breaks soil structure
-practising monoculture
-waterlogged conditions
The importance of soil structure
-there is high nutrient retention ability
-root penetration is good
-there is adequate aeration for root respiration and soil microbes
-there is high water holding capacity due to the porous crumb structure
-soil is friable, that is, it can be easily worked on
-it also increases the resistance of soil to water and wind erosion
Improvement of physical characteristics of soils
Ways of improving:
Sandy soil
-addition of manure
-addition of ant-hill soil
-addition of suitable clay soil
Clay soil
-addition of manure
-addition of lime
Loam soil
Loam soil can be maintained through:
-liming
-addition of organic matter
Soil Constituents
Soil Composition
-the soil is composed of rock particles (mineral matter), organic matter, water, air and
living organisms. The percentage composition of the constituents is as shown in the
figure below:
Soil composition
Air
25%
Water
25%
Mineral matter
45%
Organic matter
5%
1. Mineral matter
-the weathered rock particles or mineral matter are also called inorganic matter,
meaning they are not of plant or animal origin.
-the majority of Zimbabwean soils are known as mineral soils because they have a
high percentage of mineral matter. They are derived from the weathering or
breakdown of rocks.
-mineral matter forms a greater part of the soil, making 45% of the soil by volume.
2. Organic matter
-organic matter may be fresh leaves, plant stalks or droppings of animals.
-it may also be decomposed plant and animal matter
3. Soil air
-soil air consists of oxygen, carbon dioxide, nitrogen and water vapour.
-it is found in the spaces between the soil particles.
-the oxygen part is essential for root respiration of soil organisms, germination and
many chemical processes occurring within the soil.
-soil aeration can be improved by:


Applying organic matter to the soil, for example, farmyard manure, compost
and green manure. These give the soil a crumb structure which provides
adequate air space.
Improving drainage of waterlogged soils. If a soil is waterlogged it means all
the air spaces are filled with water. By draining this excess water air will
occupy these spaces.
4. Soil water
-soil water is important because it:
i.
ii.
iii.
iv.
Aids the germination of seed
Aids weathering since weathering occurs in a moist environment
Dissolves nutrients which are then absorbed in solution by the plant
Keeps plant cells turgid
-soil water can be classified into three types which vary in their availability to plants.
These are:
Types of soil water
1. Free or Gravitational or Drainage water
-this is excess water which a soil cannot retain and is drained downwards through
the soil by the force of gravity.
-it is more than the soil can hold and therefore moves down.
-this type of water is undesirable because it leaches (washes down) plant
nutrients out of the crop’s rooting zone and thus making the unavailable to plants.
-it is also undesirable because it reduces soil aeration by filling up the air spaces.
2. Hygroscopic water
-this is an extremely thin layer of water around each and every soil particle which
is absorbed from atmospheric vapour.
-it can only be seen after heating air-dried soil
-it has no value to plants because it exists as a very thin film with a very high
force or tension. This force is so high that plant roots cannot extract or absorb
this water.
3. Capillary water
-this is water which surrounds soil particles in a thin layer outside the hygroscopic
layer.
-it moves from wet to dry areas or from the water table upwards in all directions
-it is held in small pores called capillary pores and also moves through these
pores to drier parts of the soil.
SOIL TEMPERATURE
-temperature is the degree of hotness or coldness of a body, for example
atmospheric air and the soil.
-it is important for a farmer to know both the maximum and minimum
temperatures for each day as both extremes can have adverse effects on crop
growth.
-in agriculture we are more interested in soil temperature. Soil temperature is
directly related to the amount of heat (warmth) within the soil environment.
Warmth of the soil is important because:
i.
ii.
iii.
iv.
It is necessary for germination
The uptake of water and nutrients by crops is higher in warm soils than in
cold ones
Increased growth rate in (ii) above means crops and fruits open earlier
There is increased activity of soil micro-organisms resulting in:
(a)increased breakdown of organic matter with subsequent release of
nutrients
(b) nitrogen being readily available through nitrification
Optimum temperature range for :
-the maximum temperature for germination is 38oC and the minimum is 5oC. The
optimum is 30oC.
Effects of excessively high temperatures
-very high temperatures usually about 300C damage crops through wilting,
scorching and death. Even with moisture available in the soil the plants are unable to
cope with the rate of water loss through transpiration which is greater than that of
uptake from the soil.
-if the soil is exposed to direct sunlight it might be so hot that the roots near the soil
surface may die.
-at high temperatures, plants may abort as flowers are forced to drop and no fruit set
will take place.
-some plants may ‘bolt’ when they should be growing vegetatively.
-seeds may fail to germinate.
-microbial activity is reduced.
Methods of reducing effects of excessively high temperatures
1. Supply of adequate water through irrigation.
2. Mulching – covering the soil surface with a layer of plant material (grass leaf,
litter, compost, manure or crop residues). The mulch’s function is to reduce
water loss through evaporation, slow down temperature fluctuations and
reduce weed growth.
3. Shading of transplanted seedlings – this involves the sticking of leafy twigs
around a seedling soon after transplanting to provide some shade. The shade
prevents excess heat on the seedling and reduces the amount of evaporation.
This improves the survival rate of seedlings.
4. Transplanting under cool (such as late afternoon) or cloudy conditions.
Effects of excessively low temperatures
-very low temperatures which occur at certain nights and reach or go beyond the
freezing point (00C) cause frost.
-crops differ in their susceptibility to frost and the following damages can be inflicted
on the crop:
1. Tissue necrosis (death)
-the leaves and stems of affected plants are killed if temperature goes below freezing
point.
-the affected plant tissues turn brown.
-the most affected plants in Zimbabwe are tomatoes, potatoes, coffee and tobacco
seedlings.
2. Injury to flower buds and flowers
- in wheat the flowers become sterile and therefore produce no seed if exposed to
more than four hours at -2oC . The damage increases with decrease in temperature.
3. Fruit injury
- the fruit skin gets discoloured resulting in the lowering of fruit quality.
4. Injury to underground storage organs
- potatoes and onions show brown patches if bitten by frost
5. Reduced germination of seeds and reduced plant growth rate.
Methods of reducing effects of excessively low temperatures (frost)
Protection measures can be divided into long and short term methods.
(a) Long term methods
 Avoid areas prone to frost such as valleys and lower slopes. This
applies to tea, coffee and tobacco seedlings (sown in winter).
 Choose planting dates which avoid frost hitting the crop at its
susceptible growth stage. In wheat this is done by planting it in early
May so that flowering does not coincide with frost.
 Construct frost barriers – a barrier of thatch grass around a crop will
guard against cold air. This is suitable for tomatoes and tobacco
seedbed sites.
 Soil management done by keeping the soil:
(i)
Compact - excludes too much air (poor heat conductor). This
allows more heat to be conducted to the surface.
(ii)
Free of mulch - mulch produces air pockets which result in poor
conduction of heat.
(iii)
Moist soil – a better conductor of heat than dry soil.
(iv)
Uncultivated since cultivation creates air pockets.
(b) Short term methods
These methods can be used when there is a high likelihood of frost occurring
on a particular night.
 Sprinkling (irrigation) – water is sprinkled continuously once the
temperature reaches 1oC until the danger of frost is over. Thus water is
warmer than atmospheric air , and therefore the latter is warmed.
 Creating fires – this is achieved by burning diesel oil, old worn-out
tyres, crop residues or grass.
Soil fertility -fertilizers
Methods of fertiliser application
i)
Broadcasting- this is done by spreading fertilizer uniformly on the soil
surface
-
This method is usually done before planting and the fertilizer is incorporated
into soil through discing or ploughing under.
Advantages- it can be done by hand or by machine and it has low labour
requirements and it is fast.
Disadvantages- nutrients cannot be fully utilised by roots as they are not
concentrated in the root zone, weed growth is promoted
ii)
Foliar application
This refers to spraying of fertilizer solutions on the leaves of growing plants, some
nutrients are readily absorbed by the leaves e.g. zinc, boron, iron and
manganese which are dissolved in water and absorbed,
Advantages- effective as fertilizer is applied directly on to plant, and the fact that
it can be applied together with pesticides to reduce costs.
Disadvantages- if amounts are not correct i.e. excess amount it may result in
scorching of leaves and the method is only limited to micro nutrients
iii)
Fertigation
This is the application of water soluble fertilizers to crops through irrigation water.
The fertilizers are then carried to the soil by water in solution.
Advantages- very effective as nutrients in solution are easily absorbed by plants.
Disadvantages- high chances of leaching in sandy soils
iv)
Hill placement
This is when fertilizer is placed on the side of every plant, usually a standard cup
is used in such a way that each cup corresponds with a certain mass of fertilizer.
Advantages- minimum contact between the soil and fertilizer, weeds do not use
fertilizer as it is localised to the plant, the fertilizer is localised to the plant and
nutrients subsequently are close to the root zone and the next crop in the cycle
also benefits from the fertilizer.
Disadvantages- requires a lot of labour.
v)
Banding
A continuous line of fertilizer applied in furrows alongside planted crop rows. the
fertilizer is placed deeper than the seed on the side. This method can be done also
on growing crops
Advantages-no direct contact between seed and fertilizer.
Disadvantages- it is time consuming and requires machinery
vi)
Dollop method
This is done by making a small shallow hole where fertilizer is placed and coverd by
soil.
Advantages- prevents loss through volatilisation
Disadvantages- labour intensive, and poor nutrient uptake
Fertiliser application quantities per given area
Fertiliser application per given area is determined by various factors including:-
-the crop type.
-the type of fertilizer.
-the method of fertiliser application.
-the fertility of the soil.
-recommendations made by soil scientist after doing soil testing.
-previous experience of the farmer on the field in question.
Timing of fertilizer application
Basal dressing
This is when fertiliser is applied before or at planting.
Basal dressing can be done using compound and phosphatic fertilisers as well as
organic manure.
Top dressing
This is when fertiliser is applied after emergence, straight nitrogenous fertilisers are
usually applied as top dressing.
Top dressing can be a single once off application or a series of split application. In
split application, a fraction of the total fertiliser required is first applied and the
remaining amount applied after a certain period.
Soil sampling
This refers to systematic collection of a representative soil sample from a field of soil
analysis.
Principles to be followed when sampling soil:-A sample is usually collected by taking a minimum of 10 sub samples which are
collected in a zigzag or diagonal manner in the field and mixed to make a composite
sample.
-Avoid collecting soil from previous crop rows as this might distort values.
-Anthills should also be avoided.
-Clean tools must be used.
Importance of soil sampling.
-farmers can find out the physical, chemical and biological properties of soil as
analysed by soil chemists using special equipment.
- Soil pH is tested in order to recommend whether to lime the soil or not.
-Soil is also tested for nutrients to determine the fertiliser recommendations specific
to the soil and the type of crop to be grown.
Methods of soil sampling
There are two common methods of soil sampling:
1.Traversing – this is when samples are taken following the diagonals of a piece of
land
(leave 5 lines for diagram)
2.Zig-zag pattern – this is when locations for soil sampling are marked in the form of
a Z shape
(leave 5 lines for diagram)
Soil pH and Liming
Soil pH is the measure of acidity or alkalinity of the soil, soils below pH 7 are acidic
and those above pH 7 are alkaline
Testing soil for pH
Materials- universal indicator or pH paper, distilled water, test tubes, and soil
samples.
1. Place soil in the test tube to a height of 2cm. Add distilled water to almost fill
the test tube.
2. Add a few drops of universal indicator solution and shake well.
3. Leave the test tube to stand until the solution is clear.
4. Read off the pH on the universal indicator colour chat.
If using indicator paper, dip the pH paper into the solution once it has settled.
Influence of soil pH
-soil pH affects the availability of important plant nutrients, under extremes of both
acidity and alkalinity most nutrients are not available for use by plants.
-nitrogen fixing bacteria and bacteria that are responsible for decomposition of
organic matter function best at a pH range of about 6.5 to 7.5.
-plant cells die and there is tissue necrosis under very acidic and very alkaline
conditions, this results in the death of plants.
Methods of correcting soil pH
-soil acidity can be corrected by adding lime. Lime is any compound of calcium
and/or magnesium that is used to correct soil pH and nutritional disorders.
Types of lime
-quick lime (calcium oxide).
-dolomitic (calcium magnesium carbonate), this type or lime contains both calcium
and magnesium.
-hydrated or slaked lime (calcium hydroxide).
-ground limestone/calcitic lime (calcium carbonate)
Importance of liming materials
-Liming reduces acidity to a point where most plant nutrients are available.
-it adds nutrients calcium (for cell wall formation), magnesium (chlorophyll formation).
-calcium flocculates soil particles into a crumb structure thereby improving soil
structure.
-lime also increases nodulation of legumes thereby increases nitrogen fixation.
-soil microorganism activity increases.
The difference between lime and fertiliser
Lime is mainly applied as a soil conditioner (raises soil pH) while fertiliser supplies
plant nutrients.
SOIL EROSION AND CONSERVATION
-Top soil contains humus and is very important for agricultural activities. The loss of
top soil makes the land unproductive for agriculture.
-soils are more prone to erosion when they are sandy, lacking humus and having no
vegetative cover.
-areas with gradients that are steep experience high rates of erosion due to high
speeds of runoff.
-Farmers’ practices may encourage or reduce levels of erosion.
Conservation methods and structures in arable and grazing lands
-these are practices meant to conserve natural resources by utilizing them
beneficially without compromising their quality and availability to future generations.
Cultural methods
1.Early planting
Early planting enables crops to establish a canopy before onset of rains. Leaf
canopy will break the impact of raindrops reducing splash erosion and encouraging
infiltration of water into the soil.
2.Intercropping
Intercropping or planting of crops of different growth habits including cover crops
such as pumpkins reduces soil erosion, thereby conserving the soil.
3.Crop rotation
Crop rotation with broad leaved plants included in rotations conserves soil by
reducing soil erosion.
4.Mulching
Mulching introduces soil cover which encourages infiltration and reduces erosion of
top soil by surface runoff.
5.Paddocking
Paddocking or rotational grazing discourages over grazing and maintains good soil
cover which reduces erosion by allowing ample time of grass regeneration between
animal grazes.
6.Correct stocking rate
Farmers should not keep more livestock than their families can sustain as this results
in overgrazing leaving soil bare and unprotected from erosion.
7.Grass planting
Planting grasses creates soil cover which protects soil from erosion, reducing runoff.
8.Destocking
Reducing number of livestock when the carrying capacity of land has been
exceeded.
9.Correct fertiliser application
Addition of organic matter.This ,improves infiltration of water whilst reducing runoff
which washes away top soil.
10.Good soil cover
Avoid burning of grasses to maintain good soil cover
Advantages of cultural methods of soil conservation


Cultural methods are cheap
They are easy to carry out on small lands


They do not reduce arable lands
These methods increase yields
Disadvantages of cultural methods of conservation



They take time to establish
Cultural methods introduce weeds
The methods can fail easily
Mechanical soil conservation methods
To control speed of runoff and allow for improved infiltration in arable lands that are
slopy, farmers should construct the following features:
1.Storm drains
These are structures dug at the upper land of the field to catch and divert storm
water to water ways. Storm drains reduce high rates of erosion through uncontrolled
runoff from heavy rains.
2.Contour ridges
Contour ridges reduce runoff speed in arable lands which washes away soil
loosened by cultivation. These are constructed inside the field to collect surface
runoff and discharge this water safely to water ways.
3.Water ways
Water ways control water paths minimizing erosion of top soil.
4.Terraces
Terraces are levelled perches of land constructed on sloping land to reduce gradient
of slope and to enable cropping with reduced run off and soil erosion.
5.Tied ridges
These are ridges made in between crops forming furrow like structures with breaks
made of soil in between to stop continuous flow of water between planted crop rows.
These ridges encourage infiltration and reduces soil erosion.
Construction of basic conservation structures
(leave half a page for diagrams)
DRAINAGE AND WATER LOGGING
Drainage: this refers to the movement of water through soil particles. Soils with
large particles have good drainage while those with closely packed particles have
poor drainage. Poor drainage leads to water logging.
Water logging: when water is applied to the soil, it fills or occupies the air spaces.
When all the air spaces are filled by water the soil will be saturated. When saturation
of air spaces persists the soil becomes waterlogged.
Effects of waterlogged soils on crop growth
-as the soil becomes waterlogged all the air from the soil is removed resulting in lack
of oxygen for roots and micro- organisms.
-the roots will not be able to respire resulting in death of plants
-aerobic micro- organisms will not be able to survive resulting in reduced microbial
activity in the soil and subsequently low fertility in the soil
-consequently because of low fertility nutrient release to plants is reduced
-fungal diseases will be on the increase causing plants to be affected and yields
being reduced
Methods of improving drainage
1. Surface drainage
-the simplest method is by digging single open drains or ditches. These are
channels which drain water to a river or waterway.
-ditches can be 1-2m deep and 50-100m apart, depending on soil type. Clay
soils need shallow drains which are close together, while sand soils need
deeper drains which are far apart.
2. Sub-surface or internal drainage
-this is the removal of excess water by downward flow through the soil.
However, this has the effect of permanently lowering the water table.
-sub-surface drainage is accomplished by:
i) digging open ditches deep enough or down to the impervious layer
ii) the use of sub-surface pipe drains- these are clay or plastic pipes laid in
ditches and covered. The pipes are perforated and water enters through the
holes
*on a small scale beds can be raised 20-30cm above the ground and this can help
drain water
-however, as the excess water moves down the soil profile it takes with it dissolved
plant nutrients such as nitrates, and these are lost from the field’s soil system
together with the water as it enters the pipe drains and gets discharged from the
field.
-the loss of dissolved nutrients due to excessive drainage, to horizons beyond the
reach of roots is called LEACHING.
Causes of leaching on arable land
-leaching is caused by excess water on the land surface and in the soil which
originates from excess rainfall; over irrigation; seepage from dams, canals and
ditches
-alternatively, it may come into the area through surface or sub-surface flow from
other areas where there is excess rainfall or irrigation
Effects of drainage on loss of plant nutrients
-leaching results in plants losing essential nutrients such as nitrogen. Due to
leaching, soluble nutrients like nitrogen need to be split applied especially in areas
with high rainfall and highly drained soils
-leaching is beneficial at times as it helps move soluble nutrients like nitrogen applied
as top dressing on the soil surface reach the plant roots
Methods of controlling leaching in arable lands
-it is difficult to control leaching in the field. Where possible, large quantities of
organic manure should be applied to sandy soil to improve soil structure and thus
reduce drainage
-ant hill soil can be applied in the field to improve the clay content of the soil and thus
reduce drainage
RAINWATER HARVESTING AND STORAGE
Methods of harvesting and storing water
a)Rain water harvesting
-rain water can be collected using various methods during the rainy season. The
collected water is stored in dams, tanks and reservoirs for use later during the dry
season.
-rain water can be harvested through the use of gutters and dwalas or domes. Water
harvested through these methods can be used to irrigate small areas around
homesteads and gardens.
1. Roofs and gutters
-rainwater that falls on roofs flows downwards to the edges of the roof where instead
of dropping to the ground the water drops into the gutters that convey the water into
storage tanks.
2. Domes and dwalas
-large granite outcrops which may be dome shaped or low lying with curved surfaces
are used to harness rain water.
-peripheral concrete structures are built around the dome or dwalas and canals to
channel water into storage tanks or dams.
b)Rain water storage
1. Dams
-soil surface runoff from rainfall collects in streams and streams supply rivers. Small
rivers feed into bigger rivers
-dams are structures that are built mostly on river gorges for the purpose of
collecting runoff that collects in streams and rivers.
2. Weirs
-these are concrete or brickwork structures that are small imitations of dams built on
rock surfaces to temporarily store water for irrigation.
-weirs may also collect flood water from the rains
GROUND WATER SOURCES
-ground water sources are crucial in supplying water for farming during dry spells.
The ground water sources can be natural or artificial. Examples of ground water
sources are:
1. Boreholes
2. Lakes
3. Dams
4. Wells
5. Rivers/ Streams
IRRIGATION
-this is the artificial application of water to the soil to meet the crop water
requirements.
-irrigation is usually done to supplement rainfall shortages and during prolonged dry
spells.
Methods of irrigation
There are basically three main methods of irrigating crops namely;
1. Surface / flood irrigation
2. Overhead /sprinkler irrigation
3. Drip irrigation
Surface/Flood irrigation
-this is a method of irrigation that moves water over the soil surface through canals
and furrows. Siphons can also be used to move water from canals into the fields.
-types of surface irrigation methods are :
i) ridge and furrow irrigation
ii) border irrigation method
iii) basin irrigation
Advantages of surface / flood irrigation



Deep irrigation can be achieved
It has low operation costs once land has been levelled
Volumes of water can be measured accurately
Disadvantages of surface irrigation methods






can result in soil erosion
uneven wetting if soil is not properly levelled
large volumes of water are required
productive land is lost to canals
changes in soil types along the water path may affect the efficiency of the
method
not suitable for sloppy land
Overhead irrigation method
-this system of irrigation imitates rainfall. Water is pumped at high pressure usually
via aluminium pipes. The water is then delivered via nozzles in a form of a spray.
-types of overhead methods :
i) sprinkler irrigation
ii) centre pivot irrigation
iii) drag hose irrigation
Advantages of overhead irrigation




can be used on all terrain without any need of levelling the land
can also be applied with fertilisers as fertigation
cools the plants
nocturnal/night irrigation is possible
Disadvantages of overhead irrigation


may wash off chemicals before they are effective
can be affected by wind



operational costs can be high such as diesel or electricity for pumping,
servicing of equipment and repairs
operation of some equipment such as the centre pivot may require skilled
labour
evaporation losses can be high
Drip irrigation
-this is a system of pipe networks set up in a predetermined pattern that supplies
water at low pressure to localized stations
-the water is discharged at each planting station adjacent to the palnt or as a
subsurface network that discharges water at the root zone
-types of drip irrigation : i) drip irrigation
ii) micro jets
Advantages of drip irrigation system
-less energy is required for pumping
-less evaporation loss
-does not cause erosion
-effective in weed control as weeds are at a competitive disadvantage as they are
not supplied with moisture and nutrients
-offers improved fertilizer placement
-less labour requirement
-reduced disease incidence
Disadvantages of drip irrigation
-expensive to install
-the pipes can be blocked
-requires clean filtered water
-pipe network may hinder other operations in the field
-plant root development is restricted
-requires careful and skilled management
Choice of an irrigation system
Choice of an irrigation system is determined by many factors:
1.Soil type
The choice of an irrigation method depends on soil type, for example, flood irrigation
methods cannot be used on sandy soils.
2.Slope of the land
The slope of the land also influences choosing of an irrigation method. Flood
irrigation cannot be used on sloping land. Sprinkler irrigation will be most ideal for
sloping land.
3.Amount of water in the source of water
Flood irrigation methods cannot be used with little volumes of water.
4.Availability of power
Availability of power affects the choice of irrigation system. Offgrid areas may use
diesel pumps or rely on methods using alternative sources of power other than
electricity.
ANIMAL HUSBANDRY
Anatomy and physiology
The Ruminant
-ruminants are animals with four chambered stomachs. These animals can digest
cellulose and they chew the cud.
-when ruminants graze, all food goes to the first stomach chamber. During rest, the
ruminant regurgitates (brings back to mouth the food that was swallowed) the food
from the first stomach in the form of a rolled boll called the cud.
-the ruminant then re-chews the food and swallows the food for the second time.
-the anatomy of the ruminant digestive system consists of the mouth, oesophagus,
rumen, reticulum, omasum, abomasum, small intestines, large intestines, rectum and
anus.
(LEAVE HALF A PAGE FOR DIAGRAM)
Functions of the ruminant digestive system organs/parts
1. Mouth – the mouth grinds or chews and moistens food with saliva
2. Oesophagus – this is a long muscular tube used to transport food from the mouth
to the rumen through the process of peristalsis. Peristalsis is the continuous
contraction and relaxation of muscles that pushes food down to the oesophagus
3. Rumen – it is the first and largest stomach chamber of the four stomach chambers
of the ruminant animal. It acts as a storage organ for food before and during
digestion
- it also contains microbes, mainly bacteria, fungi and protozoa. This helps in the
fermentation of carbohydrates, mainly cellulose to produce volatile fatty acids (VFAs)
which are an important energy source in ruminant animals. Methane and carbon
dioxide are produced as b-products of the fermentation process.
- the micro-organisms in the rumen also synthesise Vitamin B complex and Vitamin
K. From the rumen, food goes into the reticulum.
4. Reticulum – this is the second stomach where foreign particles such as pieces of
wire, sticks and stones are trapped. Food is rolled into bolus form and is sent back to
the mouth (regurgitation) for re-chewing (chewing the cud). The food is then passed
straight into the omasum.
5. Omasum – it is the third stomach chamber commonly referred to as the bible
because of its many leaf like structures that resemble the pages of the bible. Its
function is to act as a filter of fluid. It separates coarse particles from fine particles. It
also absorbs water from the digesta.
6. Abomasum (True stomach) – this is the fourth stomach similar to the stomach of
non-ruminant animals. It is the true stomach. This is where enzymatic or chemical
digestion of food begins.
- gastric juice containing hydrochloric acid, which kills micro-organisms from the
rumen and activates enzme pepsin, is added from stomach walls. Pepsin digests or
breaks down proteins into smaller units called peptones which can be used by the
body.
7. Small intestines – the small intestines consist mainly of the duodenum and the
ileum. The small intestines are the major site of digestion and absorption of
carbohydrates, fats and proteins.
- it receives secretions which are, pancreatic juice from the pancreas, and bile from
the liver.
- it has a large surface area for maximum digestion and absorption.
(i) Duodenum – it receives bile from the gall bladder of the liver. Bile neutralises
hydrochloric acid (HCl) mixed with digesta from the abomasum where conditions are
acidic and it also breaks down fats into fatty acids.
- the duodenum also receives pancreatic juice from the pancreas. Pancreatic juice
contains the following enzymes:



lipase – for the digestion of fats into fatty acids and glycerol
trypsin – which digests proteins into amino acids
amylase – which digests carbohydrates (starch) into maltose
(ii) Ileum – this is where most of the absorption of nutrients into the bloodstream
takes place.
-
The ileum walls have small finger like projections called microvilli. These
increase the surface area for absorption of nutrients from broken down food
substances.
8.Large intestines – the large intestines consist of the caecum, colon, rectum and
anus.




Caecum – for digestion of roughages by fermentation
Colon – for absorption of water from digested materials back into the
bloodstream
Rectum – for the temporal storage of faeces before they are passed out
Anus – the final outlet for the faeces
Non-ruminant digestive system
-the non-ruminant digestive system is much simpler and consists of simple stomach
chamber and is similar to that of ruminants from the abomasum downwards.
Parts and functions of the non-ruminant digestive system
1.Mouth – contains teeth that grind food into smaller pieces (physical/mechanical
digestion).
- food is also mixed, through action of the tongue, with saliva which contains salivary
amylase. Salivary amylase is an enzyme which digests carbohydrates (starch) into
maltose, a smaller unit absorbed into the bloodstream.
- saliva also softens food for easy swallowing
2.Oesophagus – this is a muscular tube which moves food down the digestive
system through systematic contraction and expansion of muscles (peristalsis).
3.Stomach – the stomach receives food from the oesophagus, mixes it and stores it
temporarily.
- the digestion of proteins and fats begins here.
- stomach walls secrete hydrochloric acid and gastric juice which contains the
enzyme pepsin which digest proteins to polypeptides, enzyme lipase which helps in
digestion of fats into fatty acids and enzyme rennin which breaks down milk proteins.
- hydrochloric acid helps to break down food into smaller pieces, and kills harmful
micro-organisms such as bacteria.
- food from the stomach is passed into the small intestines from where digestive
processes like those which occur in the ruminant animals will take place.
The table below shows the difference between ruminant and non-ruminant digestive
system
Ruminant system
Non-ruminant system
Has four stomachs (rumen, reticulum,
omasum and abomasum)
Has one stomach
Can digest cellulose in the rumen using
microbes
Cannot digest cellulose
Regurgitates (sends food back to the
mouth for second chewing)
No regurgitation
Has no enzyme in the saliva
Saliva contains enzyme ptyalin (salivary
amylase)
Animal Nutrition
-animal nutrition refers to nutritional needs and requirements for healthy and
productive growth of livestock.
-there are different types of feeds that supply nutrients in different quantities and
proportions.
-it is therefore important to carefully plan animal feeding programs. Shortage or
excess of a nutrient may result in unhealthy conditions.
Types of feeds
-feed is any material which after ingestion by animals is capable of being digested,
absorbed and utilised. Farm animals consume mainly plants and plant products as
feed. Feedstuffs can be divided into roughage, concentrate and succulents.
1. Roughages
- these are high fibre content feeds (over 18% crude fibre) which are mainly grasses,
hay or silage. They also have low amounts of proteins, energy, vitamins and
minerals. Roughages are indigestible to most animals except ruminants.
2. Concentrates
- these contain low fibre content but high amounts of nutrients. There are two types
of concentrates:
(i) Energy concentrates – these contain high amounts of energy. They include
cereals such as maize, sorghum, millet as well as their by-products and tubers such
as sweet potato, yam and cassava.
(ii) Protein concentrates – these include soya bean meal, groundnut meal and cotton
seed meal. They contain 40-50% crude protein. There are also animal sources of
protein which are fish meal, meat meal, blood meal and milk products.
3.Succulents
- these are feeds with high water content such as fresh grass, silage and legumes.
 Ruminant feeds
- Ruminants can be fed with grass and high fibre feeds as the can digest
cellulose, a tough ,material that makes up cell walls of plants.
- Straight feeds of protein or energy concentrates can also be fed to ruminants
as supplement feeds to natural forage and fodder.
- Grass, silage and hay are examples of feeds that can be fed to ruminants.
- Clean fresh water should always be available.
 Non-ruminant feeds
- Non-ruminants cannot digest cellulose and so should be fed with feeds
containing less fibre.
- Energy concentrates from cereals, cassava and yams are examples of feeds
for non-ruminants.
- Straight feeds or commercially prepared feed stuffs as well as a constant
supply of water should be fed to non-ruminants.
ANIMAL HEALTH
Notifiable Diseases
-notifiable diseases are diseases which are very dangerous and by law once noticed
or suspected should immediately be reported to the police or veterinary department.
-immediate action should be taken such as quarantine, killing affected heads and
restriction of animal movement and products.
-notifiable diseases are highly contagious, most are incurable, can wipe out large
numbers of animals and spread so fast.
-these diseases may also infect human beings (zoonotic).
-notifiable diseases also cause great economic losses and may take some time and
effort to control
Bacterial disease
1. Anthrax
-it is a bacterial disease that affects cow, sheep, goats, pigs and humans.
Cause
-Bacillus anthraces
Transmission
-
Spread through ingestion of contaminated foodstuff such as pastures
Ingestion of contaminated meat
Symptoms
-
High body temperature and shivering
Blood stained faeces, congested mucous membranes and death within
24hours.
Animals found dead without noticing any sickness
Rapid decomposition of carcass
Non-clotting blood will ooze out through natural openings such as mouth,
nostrils and ears
Treatment
-
Difficult to treat but can use antibiotics such as Procane penicillin, tetramycin
100LA
Control
-
Bury animals deeply or burn them completely
Never open carcass of animals that die from anthrax
Report any suspected animals to the veterinary or the police
Never eat any meat from animals that die suddenly
Kill infected animals
Vaccinate animals annually with anthrax vaccines
Quarantine or separate the infected animals from healthy animals
Viral diseases
1. Foot and mouth disease (F.M.D)
Cause
-Virus such as coxsackievirus A16, Picornavirus, Aphtovirus
Affected animals
-
All cloven hooved animals such as cattle, sheep and goats
Transmission
-
Ingestion of contaminated food and pastures
Air-borne
Ingestion of contaminated meat and meat products
Contact with wildlife such as buffalo
Symptoms
-
Loss of appetite (anorexia)
Extremely high body temperature/fever
Painful blisters in the mouth, tongue and feet
Saliva dribbling from the mouth which is not completely closed because of
painful blisters
Lameness due to blisters on the feet
Treatment
-
No treatment. However, one can treat wounds to avoid secondary infection
Control
-
Quarantine all suspected animals
Regular inspection at dip tanks for early detection
Control animal movement through imports and exports
Proper disposal of dead animals (burying deeply or burning completely)
Prevent contact with wmild animals
Prevention
-
Vaccinate animals before the outbreak
2. Newcastle disease
-it is a rapidly spreading respiratory disease of all poultry and other birds such as
turkeys, chickens and pigeons
Cause
-
Virus such as Paramyxovirus
Transmission
-
Air borne(aerosols)
Ingestion of contaminated food and water
Movement of contaminated people, equipment and wild birds
Symptoms
-
Difficult breathing
Coughing and sneezing
Twisting of neck
-
Yellowish diarrhoea
Sudden reduction in egg production
High death losses
Treatment
-
No treatment
Prevention and control
-
Quarantine affected flock
Vaccinate using New castle vaccines
Good hygiene practices
Exclude wild birds
Buy chicks from reputable breeders
Protozoan diseases
1. Trypanosomiasis/Nagana
- It is a protozoan disease that affects cattle, and wild animals especially
buffalos. It also affects humans (zoonotic)
Cause
-
It is caused by a protozoa known as Tryponosoma Congolence and
Tryponosoma vivax
Transmission
-
The protozoa are spread by tsetse flies (Glossina morstans species)
Symptoms
-
High body temperature/fever
Dull and rough coat
General body weakness
Watery eyes leading to blindness
Loss of appetite (anorexia)
Diarrhoea
Treatment
-
Use – (i) Berenil
(ii) Homidium
(iii) Antricide
Control/Prevention
-
Control tetse flies by use of traps and aerial sprays
Use prophylate drugs
Isolate sick from healthy animals
ANIMAL IMPROVEMENT
Genetics
-genetics is the science that studies how heritable characteristics are passed from
parents to their offspring.
-animal improvement is based on heritability or ability of a characteristic to be
passed on from generation to generation
Important terms used in genetic studies and breeding
1.
-
Gene – it is the basic unit of inheritance that influences characteristics
Genes are found on chromosomes
They are the smallest segment on chromosomes
The major function of genes is to maintain identity from one generation to
another
2. Locus – the position of a specific gene on a chromosome
3. Allele – it is an alternative form of gene
4. Chromosomes – these are thread-like double structured strands of nucleic
acids and protein found in the nucleus of living cells which carry genetic
information (genes)
5. Genotype – the genetic makeup of the organism for a specific characteristic
6. Phenotype – it is the outward appearance of an organism
- It can also be described as the observable characteristics or measurable
characteristics of an animal such as coat colour and milk yield
7. Dominant gene – a gene that masks the effect of another
- Dominant genes show their effect even if only one copy of the allele is
present, for example, an animal will have a black coat colour even any other
allele is present
- A dominant gene is always represented using a capital letter for example Bb,
capital letter B will represent the dominant gene
8. Recessive gene – a gene whose effect is masked by the presence of the
dominant gene
- Recessive genes only show their effect if an animal has two copies of the
allele, for example bb for brown colours
9. Heterozygous – it is a situation where there is one dominant and one
recessive gene in an organism, for example Bb. Such an organism is called a
heterozygote.
10. Homozygous – is an organism carrying two similar alleles on a gene locus, for
example BB or bb
MITOSIS AND MEIOSIS
-in organisms cells are always dividing, and cell division is a highly organised precise
process. There are two forms of cell division:
1)Mitotic division which is mainly for growth and repair of tissue
2)Meiotic division which is cell division for production of sex cells or gametes
(sperms, egg).
-in genetics, study is focused on how genes (factors controlling characteristics)
influence outward appearance and how the genes are shared during cell division to
maintain certain characteristics to come up with new combinations of characteristics
in organisms.
-animal improvement is based on genetic understanding as the basis of any
manipulations that can be done on organisms to result with desired characteristics
for improved production.
1 .Mitosis
-it is the division of cell nucleus into two daughter nuclei that are identical to another
and to their parent nucleus
-this is a type of cell division that maintains the number of genetic material and is for
growth and repair of tissue
-mitotic division is important in reproduction of asexually propagated plants (plants
that grow from old parts without male or female parts being involved)
-mitosis occurs in four stages which are:
1. Prophase
-chromosomes become thicker and shorter
-they appear as two sister chromatids which are held together at the centromere
-the nuclear envelope disappears
-chromosomes move to the equator
-spindle fibres become visible
(leave 8 lines for diagram)
2. Metaphase
-spindle fibres attach to centromere pulling sister chromatids apart
(leave 8 lines for diagram)
3. Anaphase
-sister chromatids separate each other moving to each pole
(leave 8 lines for diagram)
4. Telophase
-two daughter nuclei are formed
-nuclear membranes reform as chromosoomes uncoil
-spindle fibres disappear
(leave 8 lines for diagram)
Importance or significance of mitosis
i.
ii.
iii.
iv.
helps to maintain genetic stability by keeping the same number of
chromosomes from generation to generation
helps to repair damaged and worn out cells
brings about growth through increase in cell membranes
enables asexual reproduction in plants
Meiosis
-it is a form of nuclear division in which the chromosomal number is halved from
diploid (2n) to haploid (n), hence it is called reduction division
-meiosis occurs in sex cells only
-it results in the formation of four daughter cells
Stages of meiosis
First meiotic division
1.
2.
3.
4.
Prophase 1
Metaphase 1
Anaphase 1
Telophase1
Second meiotic division
-this second stage of meiosis is similar to mitosis
1. Prophase 2
2. Metaphase 2
3. Anaphase 2
4. Telophase 2
Significance of meiosis
i.
Results in the formation of sex cells (gametes)
ii.
Brings about variation in organisms through crossing over and random
assortment
Differences between mitosis and meiosis
Mitosis
Meiosis
Effects of environment on genetics
-the environment may change the phenotype ( observable characteristics) of an
organism. For example, if two genetically identical organisms are kept separately in
two different environments, their phenotypes may not necessarily be the same
-degree of expression of a gene can be influenced by the environment.
Environmental factors that affect phenotype may include:



Nutrition (amount and quality of feeds)
Disease prevalence
Climatic factors like temperature and rainfall
FARM STRUCTURES AND MACHINERY
Farm implements maintenance
Importance of farm machinery maintenance



Well serviced and maintained machinery results in timeous operations on the
farm due to reduced breakdowns
Efficient management and operation of farm machinery offers better
opportunities for cost saving and improved productivity
Farm machinery maintenance guarantees positive return on capital
investment on the machinery. Poor or inefficient operations are costly in terms
of value invested on the machinery
1.The Plough
-it is responsible for turning, inverting and pulverizing the soil
-the plough is made of carbon steel or cast iron
-the plough has its different parts bolted together
-it cuts, loosens and inverts the soil
-depth of ploughing depends on crop root development, rainfall, soil texture and
availability of draught power
-due to the nature of the work it does, there is need for regular maintenance of the
plough by the farmer
(leave half a page for diagram of the mouldboard plough)
Plough maintenance
Daily maintenance
1. Lubrication
 Before starting work each day, greasing should be done according to the
greasing instructions in the operator’s manual
 Greasing points are normally the disc bearings and tail wheel bearing. Some
ploughs are fitted with maintenance-free bearings which do not require
greasing
2. Cleaning
 Remove soil, grass or weeds which may be on the plough after use. If
possible, wash the plough to remove any remaining dirt.
3. Routine checks
 Check wear on parts in constant contact with the soil during operation
4. Tightening
 Nuts and bolts should be checked for looseness and should be tightened if
necessary
Seasonal maintenance
Including the above, also:



Check all parts of the plough and repair or replace worn or broken parts
Before storing the plough, protect the discs against rust by applying a rust
inhibitor or old engine oil
Further protection of the plough parts can be provided by painting them before
storing in a safe place
Plough storage
-when field operations with the plough have been completed, store the cleaned,
repaired plough in a protected dry place
Plough setting
-the correct depth for ploughing is obtained by first loosening the adjusting bolt, or
taking the pin out of the depth clevis and then;


Raising the hitch for deeper ploughing
Lowering the hitch for shallow ploughing
-the length of the trek train also affects the depth of ploughing. Normal chain length
is 2.9 metres. A longer chain will cause the plough to go deeper anda shorter chain
will cause the plough to go shallow.
-the width of cut can also be adjusted as follows:


Sliding the hitch to the left (towards the unploughed land) will move the plough
to the right and make the cut narrower
Sliding the hitch to the right (away from ploughed soil) will move the plough to
the left and make the cut wider
2.Cultivators
-cultivators are also known as tillers
-these are implements which stir the land and break up furrow and clods left by the
plough
-they destroy grasses and weeds that grow after ploughing by uprooting and
exposing them to sunlight where they dry up
-a cultivator consists of a frame with a number of tines for breaking and mixing the
soil. The tines have replaceable shares or points and various designs are used for
different types of work
-working depth is generally controlled by a tractor hydraulic system
-some tined cultivators have a crumbler roll attached at the rear which helps to break
up clods
Maintenance
Placement of tines
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Worn out tines should be replaced
Tines should be properly adjusted and tightened
Oiling and lubrication of movable parts should be done when necessary
Trash trapped on the implement must be removed after use and before
storage
Store in a safe dry place
3.Harrow
-a harrow is a universally used implement and is as old historically as the plough
-the main function of the harrow is to sort out clods of varying size, leaving the
unbroken large size clods on the surface. Its action causes the smaller particles to
filter downwards thus leaving the larger ones on the surface
-the harrow is very effective in destroying small weeds that are just starting, it is also
useful in covering broadcasted seeds and in breaking crust
-the spring tines are bolted and staggered on the frames to avoid clogging during its
operation
There are two types of harrows: 1) Disc harrow
2) Tine harrow
Maintenance of a disc harrow
-a disc harrow is a land preparation implement drawn by a tractor. It is mainly used
for secondary tillage operations and conservation tillage practices.
-the disc harrow can be used to pulverize soil, break clods and for levelling of fields

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Bearings must be thoroughly greased at regular intervals
All the nuts and bolts must be checked and tightened where necessary daily
before taking the implement to the field
Blunt edges of the discs should be sharpened regularly
During the slack season, the worn out parts including the bearings should be
fully replaced
It is better to coat the outer and inner surfaces ,of the discs with oil or paint
when the harrow is lying without use in slack season
Maintenance of tine harrow
-tine harrow is an implement used to level land and to remove trash from the fields.
Sometimes it can be used to cover sown seeds
-the tine harrow is much lighter than the disc harrow and can be tractor or animal
drawn




Tighten the tines or teeth daily after use
Blunt edges of the tines should be sharpened regularly
Replace damaged tines
It is better to coat the surfaces of the harrow when the harrow is lying without
use in slack season using old engine oil or paint
FENCING
-a fence is an erect structure or barrier that is constructed to make boundaries for
security and for restricting animal and people movement
-fencing is important in farms where mixed farming is practised as it enables
cropping and livestock rearing to be practiced on the same farm without damage to
crops by stray animals
-a fence can be made out of barbed wire or mash wire with wooden or metal erect
posts. Live hedges, stone walls and grass thatch can also be used as fences
-metal and wooden poles are commonly used in wire fences. However, these require
special treatments to make them last longer by making metal withstand rust and
making wood withstand termite attack
Treatment of fencing materials
1. Wooden poles
-wooden fencing poles should be treated so that they become more resistant to
termite attack
-treating also improves their durability
-creosote is the most commonly used chemical for treating wooden fencing poles
-the following procedure may be used to treat wood:
i.
ii.
iii.
iv.
Poles cut from the field are debarked (barks stripped off) and immersed in
water to remove cell sap (cell fluids)
The poles are allowed to dry naturally
They are then immersed in creosote and boiled for several hours. This allows
the creosote to soak into the wood
The treated poles are then allowed to cool and dry under shade for slow
drying and to give more time for the wooden plant cells to absorb more of the
chemical
-other chemicals such as grease or tar oil can also be used to traet wooden fencing
poles
2. Metal fencing poles
-metals poles are treated by coating or painting to improve rust resistance
-coating or painting creates a surface layer that prevents contact of the metal with
external conditions that cause metal rusting (moisture and oxygen)
-coating of metals is usually done to metals prone to rusting by coating them or
applying a layer of a rust resistant metal such as copper, alumininium and stainless
steel
-painting is done by first applying a layer of undercoat paint followed by applying a
surface layer of paint using a brush or through spraying
-oil paint is used to protect metal from rust. The more the number of layers of paint
coats, the greater the protection. Painting is more effective if repeated over with time.
Spacing of metal posts and wire strands
-wire and wood or meatl fence should have standard materials and should be
constructed using general spacing guidelines for strength and security
-wire fence is made of standards which are wood or metal posts erected at regular
intervals of 1.8 – 2 metres apart with about 75cm of the post buried to the ground
-generally, four strands of barbed or plain wire are nailed to wooden posts using ‘U’
shaped nails or tied to metal using soft but strong plain wire. Strands of wire can be
increased to more than four depending on the level of security required
-to prevent wire strands from sagging, droppers are tied to the wire strands
suspended. The droppers are smaller in diameter and are usually of treated wood or
metal
Spacing of standards, droppers and wire strands
1) Standards
-Standards are timber or metal pieces used as upright posts in erecting farm fences.
-the length and diameter of the posts varies and their selection depends on height of
fence required
-corner posts are usually thicker forms of uprights
-standards can be spaced 1.8 metres to 2 metres apart
2) Droppers
-these are wood lengths of 50millimetre diameter suspended between upright posts
stretching from the highest to the lowest strand. Thinner metal is sometimes used as
droppers
-spacing of droppers is usually two to three droppers between two uprights.
Droppers are attached to wire strands using soft wire
-their purpose is to prevent sagging of wire
(leave 10 lines for diagram)
3) Wire anchors
-these are structures on the fence meant to make the wire resist movement in the
direction of strain
-movement of the fence in the direction of strain results in the wire strands sagging,
compromising security offered by the fence
a) High gate post anchor – this anchor helps to strengthen poles on gate
openings. The poles experience straining pull in opposite directions and
therefore have the tendency to move apart in opposite directions
-the wire tied to the posts makes the post resist strain pull
(leave 8 lines for diagram)
b) Double wire anchor – double wire anchor is used for strengthening corner
posts which is pulled by two straining pulls that act right angles. The straining
pull will cause the corner post to lean forward into the field causing wire
strands to sag
-the double wires tied to corner posts are tied to big rocks or steel pegs to
make the posts resist strain pull and remain in position
(leave 8 lines for diagram)
c) Double box anchor – the double box anchor is used where the fence stretches
over long distances
-these are placed at regular intervals along the length of the fence and help
the central part of the fence withstand sagging
-it is just like the high gate post anchor except that the wire strands cross the
anchor posts in a double box anchor. This makes the double box twice as
strong
( leave 8 lines for diagram)
d) The stay anchor – the stay anchor is usually used on wider gate openings that
should allow heavy vehicles to pass through. In such situations, the high gate
post anchor is not applicable
-usually a metal piping or rod is bolted to the gate post at a 45 degree angle
and the metal is buried to the ground in the direction of the strain to resist
movement in the direction of strain
(leave 8 lines for diagram)
FARM BUILDINGS
-building or construction is an industry where regulations are set by the local
authority or body, such as a council or municipality to ensure that the buildings are
built to a certain acceptable standard of construction
-procedures have to be followed to ensure safety of occupants, users, passers-by or
those who work in the vicinity
-brickwork involves the use of different materials and tools to erect a wall. Brickwork
is a process of producing accurate walls according to plans.
-the construction of farm structures is guided by agricultural principles and modern
trends in research
-some farm structures can be constructed using locally available resources like
wood, thatch grass and stones. However larger buildings would need steel and
concrete as construction materials
-buildings built on the farm must be to specified standards for them to serve the
intended purpose efficiently and at minimum cost
Purpose of farm buildings
-all buildings on a farm have specific purposes. They may be used to shelter farm
animals and poultry as well as to store farm produce
-the structures include water tanks, pig sties, water troughs, dairy palours, sheds,
irrigation canals, silage bunkers, tobacco barns, silos, blair toilets and so on
BUILDING MATERIALS
1.Sand
-there are two common types of sand, river sand and pit sand.
a) River sand – is used for mixing concrete and outside plastering. River sand can
be obtained from river banks. Clay and other dust particles must be removed from
river sand by washing.
b) Pit sand – is known as fine aggregates. Pit sand is used to plaster interior of
buildings. It can be obtained from pits but should be free from top soil because it
weakens the structure. If the pit sand is not clean, it is screened to remove the
organic impurities like decayed plant matter. Screening is done by passing sand
through a wire screen.
2.Quarry stones or gravel
-quarry stones and gravel are known as coarse aggregates and are used for
concrete making.
a) Stones – are used because of their strength, durability and in some cases
availability at low cost. They, however have limitations as they are unavailable in
some localities. Where they are available, they are difficult to shape into blocks for
construction.
b) Gravel – must be screened to remove fine aggregates and organic impurities. The
impurities weaken the structure as they do not have the same properties as those of
the stones. Organic material may decompose leaving cavities within structures and
these will be weak areas on the construction.
3. Cement
-cement binds particles together to form a strong structure. One important property
of cement is that once it has set, the process is irreversible.
-cement is very ideal for construction in wet areas or where there is need for water
proof structures since cement structures do not dissolve in water for centuries.
-the constructions made with cement are highly durable structures if the mixtures of
cement, sand and concrete are done properly.
-cement is the binding material (matrix) which binds aggregates together.
Aggregates refers to the sands, gravel, quarry stones that are mixed with cement
and water to produce concrete.
-cement is made by burning a mixture of clay and chalk (or limestone). For example,
ordinary portland cement is one part clay and three parts lime.
Properties of cement
-cement makes structures with high levels of strength. The structures can withstand
a sizeable amount of load and compressional forces. Some cement types have the
advantage that they can be used in wet conditions and can still set to strong
structures such as in bridges.
Portland type of cement hardens by a chemical reaction when mixed with water
(hydration). A paste of cement and water first undergoes gradual stiffening, called
setting, but the hydration continues long after the paste has become rigid. This
results in a progressive increase in strength called hardening.
Cement types
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Ordinary Portland cement: with a ratio of 3:1 (limestone:clay)
Rapid hardening cement: it is ground to a finer powder for faster setting. It is
used where a faster rate of strength gain is necessary such as in a bridge or
dam construction.
Extra rapid hardening cement: useful in temperate zones where winter
weather conditions affect construction works
Low heat Portland cement: this type is recommended for mass concrete work
such as dams and where trapped heat would cause damage to the concrete
Sulphate resisting cement
White cement
Coloured cements
Masonry cement
4.Bricks
Types of bricks
a) Common bricks: these are general purpose bricks used where appearance is
not a factor. They are porous and cheap.
b) Face bricks: these are used on exposed surfaces where appearance is a
factor
c) Engineering bricks: these are bricks used as decorative bricks. They are very
hard and smooth in texture with a high load bearing capacity. Engineering
bricks are used for constructing bridges, durable and moisture resistant
structures.
d) Fire bricks: these are refractory to heat. They increase temperature resistance
and are used in fire places.
e) Insulation bricks: they have heat insulating ability. They are used in industrial
furnaces
f) Cement blocks: these are made of cement and sand. They double measure
brick walls internally and externally. They cover work faster as they are light
and of bigger size compared to ordinary bricks. They have poor heat transfer
and are used in cavity walls.
5.Wood
-this is a cheaper and readily available material used in farm constructions.
-
 Wood is versatile. It can be easily cut to size.
 It has limited strength under load.
 It is light and therefore is used to support roofing material
However, wood is prone to termite attack and therefore requires treatment
6.Metal
-it is used as a reinforcement material in concretes and in framework
construction.
-metal sheets are used as roofing material
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


Metal has high tensile strength; thus it can withstand heavy loads and
shearing forces
Metal is resistant to fire and termite attack but susceptible to rusting. It
therefore needs galvanising, painting or coating.
It is durable. It lasts longer.
Metal is relatively expensive.
7.Grass
- grass is used for roofing as thatch and can also be used as fencing material.


Grass is relatively cheap and locally available in most areas
It is susceptible to fire and termite attack
Factors to consider when selecting building materials
a) Stability
-the material to be used should be able to support loads, lateral forces and
expansions due to temperature and moisture changes. The material should therefore
remain stable in the face of forces and conditions acting on it.
b) Strength
-the material should be able to support its own weight, wind loads and loads imposed
by other materials used in the structure. The strength of a structure depends on the
strength of the materials used.
c) Exclusion of rain
-the ability of a material to exclude rain will depend, to some extent, on its exposure
to wind and rain
d) Durability
-durability depends on characteristics or properties of the material. Durability is the
ability of the material to endure an exposure to harsh and trying conditions.
e) Termite resistance
-it is the ability of a material to resist termite attack and exposure
f) Fire resistance
-material that is fire resistance can withstand fire attack and exposure for a
prolonged period of exposure before catching the fire.
-resistance to collapse, flame penetration and heat transmission during a fire should
take half an hour to six hours.
g) Thermal resistance
-this is the rate at which heat flows through a part of a building. It is determined by
the thermal conductivity of the material and the thickness of that material. The
material to be used should have adequate thermal storage capacity. The internal
face of walls should be at a reasonable temperature.
FARM ROADS
-farm roads are very important in day to day farm operations and it is of paramount
importance that they meet certain standards and specifications.
Characteristics of a good farm road
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Safe and accessible all year round
Must be wide enough (roads to the field must not exceed 4metres in width)
Road shape must be cambered to facilitate drainage on road surface
The road must be easy to maintain
The road must be well drained to minimise damage by erosion and free from
muddy water pools
In erosion prone areas, drainage features must be gentle to a gradient of
1:200
The road dimensions and shape
(leave 8 lines for diagram)
Road gradient
-road gradient should not exceed 1 in 20 for loaded vehicles especially during wet
weather as theis becomes a hazard.
-in the eastern highlands areas such as Nyanga, Honde Valley, Chimanimani and
other places roads can be as steep as 1:12 and cannot be used in wet weather.
Features for farm road drainage
1.Side drains
-farm roads should have side drains that collect water from the road crest. The side
drains should have mitre drains at one metre vertical interval
-the drains should be dish shaped or wide at the bottom to minimise erosupion. The
drains can also be grassed to reduce erosion and maintenance costs.
(leave 8 lines for diagram)
-where the road is not on the crest, there might be need to move or divert water from
the upper to lower side of the road. This is achieved by using culverts and inverts,
with inverts being the cheaper option.
2.Culverts
-culverts are built structures with buried concrete pipes that divert water across the
road from an upper slope to the lower side of the slope.
(leave 8 lines for diagram)
3.Inverts
-inverts are shallow depressions made of cement and concrete flat slabs built on
road surface to allow water to flow across the road without damaging the road
through erosion.
(leave 8 lines for diagram)
4.Bolsters
-gently sloping banks of gravel built across the road can also be used to divert water
from one side of the road to the other. Bolsters can be part of contour ridges in
arable land.
(leave 8 lines for diagram)
Farm road maintenance
-farm roads require regular maintenance and care from time to time to keep the
roads safe and accessible
-heavy vehicles and machinery may damage the roads during operations, by
creating tracks and furrows that may lead to erosion during the rainy season
-drainage structures need to be maintained by clearing weeds that may block water
ways so as to check erosion. However, grass should not be completely removed
from water ways but cut short to maintain soil cover.
-farm roads need to be graded to keep the surface smooth and to maintain the
camber shape for facilitation of drainage
-the road crest must always be dry in wet seasons to avoid muddy conditions
-laterite gravel may be needed from time to time to fill in potholes that may develop
with time
-it is sometimes necessary to wet the roads with a water bowser during dry seasons
to minimise erosion by wind currents, generated by moving vehicles. This also helps
to reduce ripples developing on the road surface
AGRI-BUSINESS
Opportunity cost and choices
-the opportunities which are available to the farmer in agriculture industry are quite
variable. These can best be summarised by the different branches of agriculture
which include:
1.Crop production – there are many different types of crops that a farmer can decide
to produce depending on a number of factors that will be explained later.
-the different types of crops include:
a) Cereal crop – maize, wheat , sorghum and others
b) Legume crop – groundnuts, fieldbeans, soyabeans etc
c)Horticulture or market gardening- vegetable, flower or fruit production
2. Livestock production – broilers, layer birds, rabbits, dairy and beef cattle
production
3. Forestry and Wildlife management
4. Agri-business management
5. Crop and animal breeding
6. Research and extension
7. Processing of agricultural products
Factors influencing farmers’ choices in agricultural enterprises
1. Available land
This refers to the size of the land, type of soil, topography, fertility, drainage and
others. All these have direct and indirect effects on the choice of an enterprise the
farmer can pursue. Fertile, well drained soils are generally suitable for crop
production while less fertile lands can be used for either livestock, forestry, wildlife or
any other branch of agricultural enterprise.
2. Climate
This generally refers to mainly rainfall and temperature. Different crops and livestock
are suitable for different climatic conditions. Generally, in Zimbabwe crop production
is more suitable for Region 1 and 2, while livestock, specifically cattle ranching and
wildlife is practiced in Regions 3, 4 and 5 which receive low rainfall
3. Availability of capital
Farmers with limited capital available to them have limited choices of enterprises
they can engage in. Farmers are left with very little choices as they cannot afford to
engage in capital intensive enterprises
4. Availability of market and market price
Farmers feel more secure to engage in the production of a commodity whose market
is easily available than those with market which is scarce. Farmers are generally
attracted by high market prices for their products.
5. Availability of labour
Some farmers may decide not to undertake certain enterprises because they require
a lot of labour, for example, tobacco at reaping stage.
6. Government policy
Government policy also has some bearing on the farmers’ choices of enterprises.
Availability of subsidies and favourable producer prices may attract farmers into
certain production.
7. Farmers’ knowledge and preference
Farmers generally want to engage in enterprises they have knowledge in. Individual
farmers have different preferences and tastes.
Opportunity cost
-farmers are faced with the problem of choosing between the many different
opportunities they have. For example, in crop production, one may have to choose
between maize, sorghum and field bean production. When they choose to grow
maize instead of the other crops, the opportunity cost is the money that they would
lose from not growing the next best crop among the list
*opportunity cost is therefore the next best alternative foregone when a choice has to
be made*
-another example is when a farmer has resources to produce poultry. The farmer
then chooses to produce broilers instead of layers. The opportunity cost is the
revenue that the farmer is going to lose out by not producing layer birds
-the problem of opportunity cost is one that all farmers face every time they make a
decision to produce. One cannot carry out all the enterprises considering that
resources are limited so farmers need to make wise decisions wherever necessary
Principle of demand
-demand is the quantity of a commodity that customers are willing and able to buy at
a particular price and time. Demand is mainly influenced by the price of the
commodity giving rise to the “Law of demand”
Law of demand
-law of demand states that “the higher the price of a commodity, the lower the
quantity demanded and vice versa”
-customers will buy less of a particular commodity when the price of that commodity
rises and they buy more when the price goes down
-commodity price and the quantity demanded are usually inversely related. An
illustration of the law of demand is shown in the demand schedule for tomatoes
given below:
Demand schedule for tomatoes
Price of tomatoes ($/kg)
0.5
1.0
1.5
2.0
2.5
Quantity of tomatoes demanded in kg
25
20
15
10
5
-from the above schedule, it can be noted that as the price of tomatoes rises from
$0.50/kg to $2.50/kg, the quantity of tomatoes demanded decrease from 25kg until it
reaches 5kg at $2.50/kg.
-the deamd schedule above can be presented in the form of a graph to give the
demand curve below
( leave space for graph )
Factors influencing demand
-in addition to the price, demand of a commodity is also influenced by:
1.Income of consumers
2.Price of substitutes
3.Season
4.Customers’ religion
5.Quality of the commodity
6.Taste and preferences
Principle of supply
-supply is the quantity of a commodity that producers are willing and able to offer for
sale at a particular price and time.
Law of supply
-law of supply states that the higher the price of a commodity on the market the more
the quantity of that commodity the producers are willing to sell
-from the supply schedule below, it can be noted that as the price of tomatoes on the
market increases so is the quantity producers are willing to offer for sale
Supply schedule for tomatoes
Price of tomatoes ($/kg)
0.5
1.0
1.5
2.0
2.5
Quantity of tomatoes supplied in kg
5
10
15
20
25
-using the supply schedule of tomatoes shown above, a supply curve can be drawn
as shown below
(leave space for graph)
-the supply curve goes upwards from left to right. This shows that there is a positive
correlation between price and supply of a commodity. The higher the price of a
commodity, the greater the supply.
Other factors affecting supply
1.Price of other goods
2.Production costs
3.Weather conditions
4.Technology
5.Pests and diseases