FORM 4 AGRICULTURE NOTES
GENERAL AGRICULTURE
Environmental factors
Natural disasters
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Natural disasters are events or harsh environmental conditions that threaten crop and
livestock production and survival.
Effects of natural disasters on agriculture
Hailstorm
• This is a form of precipitation that falls as ice stones of varying size.
Effects of hailstorm on crops
o Damage plant parts such as leaves, flowers, stems or even total crop destruction
o Leaf crops such as tobacco are often damaged resulting in heavy losses
o Fruits may be hit and fall prematurely resulting in serious production losses
Effects of hailstorm on livestock
o Hailstorms result in death of some small livestock and newly born animals
o Large ice stones usually kill livestock animals that are not properly sheltered
Effects of hailstorm on farm structure and machinery
o Large ice stones damage roof tops, glass window panes resulting in disruption of
operations
o Hailstorms may break farm vehicle wind screens and mirrors and other delicate parts
of farm machinery resulting in a lot of costs being incurred by the farmer in replacing
the damaged parts
Floods
• Flooding is a condition when areas that are usually dry land are covered with large
volumes of water
• Floods are a result of heavy and excessive rainfall
• Siltation of rivers and poor surface drainage increase the chances of floods
• Low lying areas e.g. Muzarabani in Zimbabwe, are prone to flooding.
Effects of floods on crops
o Crops are destroyed by flooding condition due to lack of aeration in the soil
o Flood waters weaken root anchorage and uproot crops or leave crops bent down and
covered in mud
Effects of floods on livestock
o Death of livestock due to drowning
o Destruction of pasture leading to reduced livestock feeds
o Spread water borne diseases
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FORM 4 AGRICULTURE NOTES
Effects of floods on farm structures and machinery
o Fences, animal handling facilities and farm buildings are swept away or damaged by
flood water
o Flood water damage farm roads and bridges resulting in transport and
communication problems
o Irrigation equipment and machinery is damaged by flood water
Cyclones
• This is an environmental condition where excessive rains associated high velocity winds
last for several days
Effects of cyclones on crops
o Heavy rains and high speed winds result in logging of crops leading to yield loss
o Cause flooding accompanied by leaching and poor crop growth
Effects of cyclones on livestock
o Death of livestock animals that are not properly housed or sheltered
Effects of cyclones on farm structures and machinery
o Cyclones result in flash floods which destroy roads, bridges and farm buildings
o Strong winds associated with cyclones damage roofing of farm buildings
Whirl winds
• These are high speed winds that move with a strong circular motion
Effects of whirl winds on crops
o The force of whirl winds breaks down and destroy some crops
o They cause flower and premature fruit drop resulting in yield loss
o Spread of weeds, pests and diseases
Effects of whirl winds on livestock
o Spread of air borne diseases
Effects of whirl winds on farm structures
o Destruction of roof tops on farm buildings
Drought
• Drought refers to shortage of rainfall as a result or poor rainfall distribution.
Effects of drought on crops
o Total crop failure as a result of insufficient soil moisture for crop growth
o Little or no harvest result in shortage of food and starvation
Effects of drought on livestock
o Animals die from dehydration due to shortage of drinking water
o Starvation of livestock due to shortage of food
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FORM 4 AGRICULTURE NOTES
o Reduced productivity and breeding
Heat waves
• Heat waves are periods of extreme high temperatures above the normally expected
temperatures of an area and season
Effects of heat waves on crops
o Wilting of crops when short lived
o Drying and death of crops when heat waves occur for longer periods
Effects of heat waves on livestock
o Livestock such as poultry die from heat stroke especially broilers
Veld fire
• These are wild fires that spread through grasslands and forests
• They are caused by lightning, accidents, electric faults on power lines and various human
activities
Effects of veld fire on crops
o Destruction of crops and loss of yield especially in mature cereal crops such as
maize, wheat and millet
o Destruction of forest plantations and harvested timber
o Veld fires result is followed by new fresh grass pastures which are good for livestock
Effects of veld fire on livestock
o Animals are killed by the veld fires
o Pastures are destroyed resulting in shortage of fe
Disaster risk management strategies
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Government departments have been established to predict and forecast natural disasters
so that early warning is made and disaster preparedness efforts are heightened to reduce
the impact of natural disasters
Weather forecasting
Establishment of disaster management departments
Construction of structures that reduce the impact of natural disasters such as dams,
drainage systems and fire guards
Forestry
Agro-forestry
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This involves the growing of trees or shrubs either at the same time with crops or in
rotation with crops.
Crops, animals and trees support each other and therefore increase the total productive
yield of the farm.
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FORM 4 AGRICULTURE NOTES
Importance of agro-forestry practices
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Trees have deep roots that may reach far into the soil water table. Many trees can
therefore continue to grow in the dry season without irrigation that is continue to produce
food, fodder and other tree products all year.
The tree roots take in nutrients from the deep layers of soil and bring them up to their
leaves and fruits which can contribute to a nutritious diet. When the leaves fall down they
become part of the soil organic matter which releases nutrients into the soil and make
them available to shallow rooted crops such as grasses and vegetables.
Trees provide shade for livestock.
Trees helps to conserve the soil maintaining soil structure, hold the soil together, increase
infiltration, reduces surface runoff therefore reduce soil erosion.
Some trees used in agroforestry have medicinal properties; they can provide traditional
herbal medicines.
Agro-forestry components
Agroforest trees
• The trees must not compete for resources with crops and must not produce excessive
shade for crops or chemicals that suppress growth of other plants
• The agroforest trees must have nitrogen fixing ability and deep rooted to access nutrients
beyond reach of agricultural cops
• Where livestock is included, the trees must be edible as fodder feed
Livestock
• Livestock must benefit from the tree-animal interaction whilst providing manure to the
system
Crops
• The crop must not be negatively affected by the trees included
Wildlife
Human and wildlife conflicts
Causes of the conflicts
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establishment of settlements near parks or safari areas
occurrence of drought
lack of food due to overpopulation of wildlife
isolated settlements within wildlife areas
high nutritional value of crops grown by humans opposed to flowers and other plants
found in the wild
poaching
deforestation
human population growth
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FORM 4 AGRICULTURE NOTES
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veld fires
elimination by farmers as pests.
Protection of wildlife resources
Parks and wildlife estates
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State land allocated to the protection of wildlife.
National parks
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Have the highest protection and conservation status in Zimbabwe e.g. Gonarezhou,
Matopos, Hwange etc
Botanical reserves
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Areas meant for the conservation, preservation and protection of special forests or groups
of indigenous plants e.g. Vumba, Mazowe A & B, Rusitu forest, Sibakwr Accacia forest.
Botanical gardens
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Indigenous plants are planted and grown/taken good care of e.g. Harare botanic, National
botanic garden, Vumba etc.
Sanctuaries
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Place set aside primarily for the conservation of individual species of birds and other
animals e.g. Masvingo (all animal species), Mbazhe pan (bird species) etc.
Safari areas
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These are smaller than national game parks and they provide outdoor activities such as
professional hunting, photographing and game viewing.
Recreational parks
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These are associated with large bodies of water such as lake Kariba, Mutirikwi and
Chivero and they allow outdoor activities like fishing, skiing, camping, game viewing and
boating.
Government policy on wildlife
Parks and wildlife act 123/1991 chapter 20:34
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Seeks the preservation and conservation of wildlife resources
establishment of parks and wildlife board
establishment of national parks and animal reserves (reserves, botanical gardens, safari
areas and recreation parks)
make provision for the preservation, conservation, propagation and control of wildlife
from plants indigenous to Zimbabwe and the protection of its scenery
give certain powers to intensive conservation area committee.
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FORM 4 AGRICULTURE NOTES
Voluntary Organizations in Wildlife Management
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ii.
iii.
World Conservation Union (WCU)
World Wide Fund for nature (WWF)
Safari Clan International (SCI)
These provide funds for conservation and management of wildlife.
International conventions
CAMPFIRE
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The concept was introduced to include communities in natural resources management.
It ensures that communities:
o take full charge of resource in their area
o manage and benefit from them
o benefit from hunting and selling of wildlife
o use the money to build clinics and schools.
CITES
Convention of International Trade in Endangered Species, is an international agreement.
Aims of the agreement:
i.
ii.
to prohibit trade in endangered species while allowing commercial trade in species of
wildlife that can withstand the pressure is trade
control trade in both lice animals/plants covered by the convention depending on the
appendix list.
Appendix 1
Has a list of all endangered species e.g. cheetah, African elephant, leopard, black and white
rhinoceros. Trading in these animals of their production is strictly prohibited.
Appendix 2
List of animals yet to be endangered but monitored for sustainable utilization e.g.
Hippopotamus, wildcat, Namibian seals, Nile crocodile.
Appendix 3
Designed for individual countries whose aim is to gain external resistance in protecting
wildlife e.g. NEO.
NB: animals in each of the appendixes may be removed from one appendix to the other.
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FORM 4 AGRICULTURE NOTES
SOIL AND WATER
Soil fertility
Nitrogen cycle
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The nitrogen cycle is a flow of nitrogen in different chemical forms between plants, other
organisms and the atmosphere
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Nitrogen is present in all proteins of both plants and animals
When animals or plants die the proteins are decomposed by fungus and bacteria.
The nitrates produced are reabsorbed by plants and then transferred to animals through
ingestion.
All plants and animal wastes reaching the ground are acted upon by a number of soil
organisms i.e. worms, millipedes, bacteria and fungi which change the materials to
ammonium compounds.
These are further decomposed by nitrifying bacteria i.e. Nitrosomonas which convert the
ammonium compounds into nitrites and Nitrobacter which converts nitrites to nitrates. It
is in this form that nitrogen is mainly absorbed by plants
About 79% of air is Nitrogen. A small portion of this is changed into ammonia by
lightning then to ammonium compounds which can be absorbed by plants.
A small fraction of the Nitrogen in air is converted into nitrates directly by nitrogen fixing
bacteria called Rhizobium which lives in nodules of some leguminous plants.
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FORM 4 AGRICULTURE NOTES
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If aeration is poor, certain bacteria use oxygen in the nitrates and in the process release
nitrogenous gas to the air in a process called denitrification.
Water conservation
Water pollution
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This is the introduction of harmful substances to water.
These substances are called pollutants.
Causes of water pollution
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Industrial wastes can enter water bodies and create a high percentage of toxic materials
and kill fish and other aquatic organisms.
Litter may be disposed in rivers and dams.
Sewage material may end up in water bodies and cause eutrophication (excessive
multiplication of aquatic plants due to excessive nutrients in the water especially
nitrogen)
Agricultural chemicals may contaminate underground water, rivers and dams.
Gold panning
Recreational activities e.g. car racing may pollute through oil and fuel leakages into the
water.
In mining, use of chemicals such as cyanide in gold treatment can cause water pollution.
Effects of water pollution
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Eutrophication resulting in plants blocking pipes and canals used in irrigation.
Fish in water is killed by toxic substances dissolved in water.
Some chemicals may affect the soil pH resulting in poor plant growth and low yields.
Some pollutants can cause diseases to plants.
Ways of reducing water pollution
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Education of the citizens on the problems of water pollution and possible solutions
Enforcement of environmental laws that prohibit water pollution
Minimum and correct use of persistent agro-chemicals
Proper disposal of sewage and domestic wastes
Treatment of industrial wastes
Correct application of fertilizers and irrigation water
Water legislation
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The harnessing and use of water in Zimbabwe is controlled by the government of
Zimbabwe through the Water Act which is administered through the Zimbabwe Water
Authority.
The main aim of the Water Act is to decentralize the control and use of all forms of water
(ground and surface) as well as abolish private ownership of water.
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FORM 4 AGRICULTURE NOTES
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Pollution of water is a punishable offence under the Water Act.
Authority to use water
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The permission to use water is called Water Right and is given by the Water Court
following the provision of Water Act.
The permission or authority is given for the use of public water for:
o Agricultural purposes (irrigation, fish farming, operation of feedlot in which 12 or
more cubic meters of water per day is used for a period time which exceeds 6
months.)
o Institutional purposes (used in boarding houses, guest farms, hostels, recreational
clubs, missions or boarding schools and permanent work force)
o Electrical purposes (electricity generation)
o Railway purposes (steam engines)
o Mining purposes
o Local authority or township purposes
o Road construction purposes
The Ministry of Rural Development and Water Resources
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Holds water rights for government irrigation schemes in communal areas.
Individuals, groups of individuals, mission and boarding schools must have their
applications approved by the district council before water rights are given.
No water rights are needed for drawing water from wells, boreholes or mineshafts.
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FORM 4 AGRICULTURE NOTES
Irrigation
Irrigation equipment
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Equipment comprises of pumps, pipes and risers (sprinklers).
Pumps
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Pumps are driven by diesel or petrol or electricity.
The main function of pumps is to draw water from water sources (dams, canals,
boreholes, rivers, weirs) to the field through pipes.
Irrigation water has to be raised from its source to the field surface.
Efficiency of the system depends on the application of sound principles in the design.
Basically there are four principles involved in pumping
i.
Atmospheric pressure
ii. Positive displacement
iii. Centrifugal force
iv.
Movement caused by differences in specific gravity
Common types of pumps used in Zimbabwe
Hydraulic ram
• Can raise water from a lower height to a greater height.
• The devices is commonly used in hilly areas where there is considerable difference
between altitude of the river and the field.
Principles
Water flows from the supply source into the inclined supply pipe. The waste valve open
to allow water to escape and free flow is set up along the pipes. Pressure builds up in the
valve box to overcome the weight of waste valve. The waste valve close causing rapid
increase in pressure in the valve box. The increase in pressure causes the delivery valve to
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FORM 4 AGRICULTURE NOTES
open and water escape into their vessels when it compresses the air and flow out through
a discharge pipe.
Maintenance
o Maintenance costs are very low.
o Replace valves if they are worn out.
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Reciprocating pump
This uses atmospheric pressure to raise water in a pump column.
A piston in the body of the pump moves up and down to displace air from the pump
column.
This creates a vacuum which permits the force of atmospheric pressure to push water
from the well into the pump column.
It is found in almost all rural areas of Zimbabwe.
Can be single acting when they have one discharge for every two strokes of the piston or
double acting when water is pumped on both in and outward movement of piston.
This is hand operated or wind operated.
Centrifugal pump
It is a rotatory machine with two basic parts; the rotary impeller and easing.
The impeller is fitted with vanes in curved form.
Vanes are arranged in a circular array around an inlet opening at the centre.
When the impeller rotates inside a closed fitting easing water is drawn in at the centre.
The centrifugal force then throws out the liquid through openings at the side of the casing.
This is powered by electric motors or diesel engines.
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FORM 4 AGRICULTURE NOTES
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Chain pump
It is commonly used in Mutasa district of Manicaland where a non-governmental
organisation Pump Aid Zimbabwe help to install them.
Consists of an endless rope fitted with rubber discs or washers placed at intervals of about
20 cm.
A series of knots along the rope are tied to prevent movement of the rubber discs.
The rope passes through a notched shaft outside, which is mounted on a suitable platform
on top of a well.
The bottom of the pipe is submerged in water below the surface.
The rubber discs have the same diameter as the inside of the pipe.
When the wheel is turned each disc brings up a volume of water.
This type is mainly hand operated.
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FORM 4 AGRICULTURE NOTES
Maintenance
o The pump has low maintenance cost.
o Rubber and ropes have to be replaced if they are worn out.
o Movable parts have to be oiled to reduce friction.
Pipes
• Some pipes are large and laid underground from the pumps to the fields.
• Once in the field, vertical risings to the surface are interspaced.
• Vertical risings are called hydrants, are the points that supply water to the surface pipes
which discharge water to crops through risers.
• The surface pipes are smaller in diameter than underground pipes
Risers
• These are upright pipes connected to the water supply pipes on which sprinklers are
connected
Sprinklers
• Are fitted to risers.
• Break water into fine droplets, spreads the water over a large surface area and reduce
damage to crops.
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FORM 4 AGRICULTURE NOTES
CROP HUSBANDRY
Plant processes
Respiration
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Respiration is the breakdown of carbohydrates to release energy.
Aerobic respiration
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Occurs when oxygen is available.
It is the source of energy for growth and other plant processes.
Produces carbon dioxide and water vapour as by-products.
glucose + oxygen → carbon dioxide + water + energy
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It occurs in all living organisms at all times and is important because it releases energy
required by plants for:
i.
Cell division and growth
ii. Chemical synthesis of substances
iii. Active transport of mineral salts from the soil into the roots
Respiration occurs in the mitochondria.
It occurs in stages and each stage is catalysed by an enzyme.
The energy released is used to build up an energy rich compound called adenosine
triphosphate (ATP) from adenosine diphosphate (ADP).
ADP + phosphate + energy → ATP
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When the bond is broken, energy is released for use in cells.
Anaerobic respiration
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Not all living organisms and plants require free oxygen to grow.
In anaerobic respiration organisms breakdown sugars to produce alcohol and carbon
dioxide with the release of little energy.
Anaerobic respiration is used by brewers and bakers who use yeast.
Yeast is capable of anaerobic respiration where it breaks down sugar into alcohol
releasing carbon dioxide and some energy. The process is called fermentation.
glucose → alcohol + carbon dioxide + energy
Comparison between photosynthesis and respiration
Photosynthesis
Takes place only in the presence of light in
plant cells.
Uses carbon dioxide and produces oxygen.
Light energy is stored in carbohydrates
Plant gains weight.
Chlorophyll is essential.
Occurs in the chloroplast
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Respiration
Occurs in both dark and in the presence of
light in all living organisms.
Uses oxygen and produces carbon dioxide.
Energy is liberated from the breakdown of
carbohydrates.
Plants lose weight.
Chlorophyll plays no part.
Occurs in the mitochondria
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FORM 4 AGRICULTURE NOTES
Plant tropisms
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These are growth movements by part of a plant in the direction of a stimulus.
The stimulus can be light, gravity or water.
If a plant grows towards the direction of a stimulus, it is described as positively tropic to
that stimulus.
If the plants grow away from the stimulus, it is described as negatively tropic to that
stimulus.
These growth movements are as a result of the effect of plant hormones called auxins
which are produced at the tips of both shoots and roots.
Auxins stimulate growth in shoots but inhibit root growth.
Phototropism
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This is growth movement of shoots in response to light.
Shoots are positively phototropic i.e. they grow toward light.
When light is coming from all directions, auxin produced from the shoot diffuses
downwards away from light and the shoot continues to grow normally i.e. upwards.
If light comes from one side, auxin moves from the illuminated side to the dark side
where it stimulates growth. This will uneven growth rates with a higher growth rate on
the dark side.
The increased growth rate on the dark side will result in the shoot bending towards the
source of light.
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FORM 4 AGRICULTURE NOTES
Geotropism
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This is growth movement in response to the effect of gravity.
Shoots are negatively geotropic while roots are positively geotropic.
Hydrotropism
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This is growth movement in response to water.
Roots are positively hydrotropic while shoots are negatively geotropic.
Importance of plant tropisms
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It enables plants to get their nutritional requirements e.g. plant roots respond positively to
gravity and water. This enables the plant roots to grow towards the source of water as
well as nutrients in the soil.
Plants are able to get sunlight and there is better gaseous exchange when shoots grow out
of the soil.
Growth habits of climbers is enhanced as plants wind themselves up trees in order to
minimize the surface area that is exposed to sunlight.
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FORM 4 AGRICULTURE NOTES
Crop protection
Agro-chemicals
Types of agro-chemicals and their uses
Type of chemical
Pesticides
Fungicides
Acaricides
Herbicides
Nematicides
What it controls
Pests
Fungi
Ticks and Mites
Weeds
Nematodes/Eelworms
Toxicity levels of agro-chemicals
The use of colour triangles
Colour of triangle
Green
Amber
Red
Purple
Meaning
Caution
Poison
Very dangerous poison
Extremely poisonous
Safe use and storage of agro-chemicals
1. Read the label and follow instructions of use carefully.
2. Move the chemicals safely.
3. Wear protective clothing when using chemicals e.g. rubber gloves, rubber boots, long
trousers and shirt or overalls, respirator or a cloth to cover the nose and mouth, and
goggles.
4. Never eat, drink or smoke when using chemicals.
5. Practice hygiene.
a) If chemicals gets onto your skin wash with water, do not rub it off the skin.
b) Wash hands and face thoroughly after spraying.
c) Wash used protective clothes before storing them.
6. Avoid equipment accidents.
a) Check equipment for leaks, weak hose and faulty connections.
b) Avoid spilling or pouring chemicals near ditches, wells and other water sources
because they can poison people and other organisms.
7. Inform the equipment operator about the chemical being applied and its dangers so that
he/she exercises caution.
8. If the chemical was in bags burn them in a safe place and avoid inhaling smoke from the
burning bags. If it was in tins or hard plastic containers, crush them and bury them in an
areas where ground water will not be contaminated. Do not use the containers to transport
or store drinking water, milk or beer.
9. Store the chemicals well
a) Store the chemicals away from living quarters, animal pens and water supplies.
b) Keep the chemicals out of reach of children.
c) Place warning signs in the storage area.
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FORM 4 AGRICULTURE NOTES
Knapsack sprayer
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This is the most commonly used sprayer on both small and large scale chemical spraying
It comes in different sizes and shapes ranging from 5 to 15 litre tank capacity
The knapsack sprayer is carried as a back pack and the pressure pump is operated by one
hand while the other hand holds the lance
Parts of a knapsack sprayer
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FORM 4 AGRICULTURE NOTES
ANIMAL HUSBANDRY
Anatomy and physiology
Reproductive system of a ruminant
The reproductive system of a bull
Testis
• They are oval in shape, hanged outside the body in a sac like structure called the scrotum.
• The scrotum protects the sperms and makes sure the temperature is ideal for sperm
production.
• The testis are responsible for the formation of sperms (male sex cells) and produce
testosterone, a hormone which facilitates ejaculation
Epididymis
• Stores sperms while they mature before ejaculation.
Sperm duct
• Carries sperms from the epididymis to the seminal vesicle
Seminal vesicle
• Provides nutrition to sperms
Prostate gland
• Assist in transportation of sperms also supplies nutrition to sperms
Cowper’s gland
• Provides fluids which assist sperms to survive
Urethra
• Passage for sperms and urine
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FORM 4 AGRICULTURE NOTES
Penis
• Male organ for copulation
The reproductive system of a cow
Ovary
• Produces female sex cells (ova)
• Produces female sex hormones (oestrogen and progesterone)
Fallopian tube (oviduct)
• This is where fertilisation takes place.
• Provides passage for ova from ovaries to the uterus
Uterus
• This is where implantation and development of the embryo takes place.
• It nourishes and protects the foetus throughout the gestation period.
Cervix
• This is a narrow neck of the uterus.
• It prevents entry of bacteria into the uterus
• It closes after fertilization to prevent the foetus from early release.
Vagina
• It is where sperms are deposited during copulation.
• It is also the birth passage
Vulva
• It is the posterior part and visible part of the reproductive system.
• It absorbs pressure during copulation and protects the vagina.
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FORM 4 AGRICULTURE NOTES
Animal nutrition
Maintenance, production and balanced rations
Maintenance ration
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A ration given to animals to keep them alive, without gaining or loss of body weight/size.
Production ration
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A ration which is supplied over and above the maintenance ration to enable animals to
produce energy or products such as meat, milk, eggs, wool, etc.
Balanced ration
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This is food which contains important nutrients in measured quantities.
Pearson’s Square method
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Pearson’s Square method is used to determine the proportion of feeds to be added to give
a ration with the correct amount of nutrients.
For example, calculate the mixing ratio of feed stuff with 10% digestible crude protein
(DCP) if groundnut cake has 40% DCP and maize 8% DCP.
40% Groundnut cake
10 – 8 = 2
10%
8% Maize meal
Mixing ratio =
=
40 – 10 = 30
2
1
Maize meal
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30
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Groundnut cake
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FORM 4 AGRICULTURE NOTES
Small livestock production
Layers
Preparation of eggs for marketing
Egg collection
• Eggs are collected and put in a basket or bucket with clean dry grass inside
• Calculate laying percentage to determine whether it is worthwhile to keep the layers using
the following formula:
𝑙aying percentage (%)=
number of eggs collected
total number of laying birds
Cleaning eggs
• Clean the collected eggs using a damp piece of cloth or steel wool to remove chicken
droppings or any dirt on eggs.
• Remove cracked eggs.
Grading eggs
• Eggs are graded into large, standard, medium and small according to their weight, size
and colour.
Grade
Large
Standard
Medium
Small
• Separate brown eggs from white eggs.
Weight
> 62.5g
55.0g – 62.5g
45g – 54g
40g – 44g
Packaging
• Eggs are packed in crates then the crates are placed inside cardboard boxes for
transportation to the market.
• Pointed end of the eggs should face down so that air circulates freely into the eggs and
keep them fresh.
Off-layers
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An off-layer is a chicken which is no longer able to lay eggs.
Off-layers are not productive and should be slaughtered to minimise feeding costs.
Slaughtering off-layers is a way of boosting income from meat sales.
Slaughtering and dressing off-layers
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Slaughtering and dressing is a process that is done in preparation of livestock for the
market as meat product.
It involves stunning, killing, scalding, evisceration, cleaning and packaging of the carcass
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FORM 4 AGRICULTURE NOTES
Stunning
• Stunning should be done by knocking the sense out of the off-layer before cutting the
throat
• This can be achieved by neck dislocation, knocking on the back of the head of the bird
using a heavy object or electric shocking
Cutting and bleeding
• After stunning, the off-layers are placed in slaughtering cones for neck cutting and
bleeding
• Cutting is done to open blood vessels to allow draining of blood from the bird
• Bleeding should be allowed to take place for one or two minutes
• Blood not drained out of the bird will:
o taint the meat giving it the taste of blood
o make the meat go bad easily
o give the carcass a purplish discolouration
Scalding
• This is the removal of feathers after bleeding
• The birds are immersed inti hot water (50-54oC) for about one minute
• Hang the bird by the legs over a clean table and start by plucking the tail and wing
feathers then the rest of the body
• After plucking, pin feathers and some hairs can still be seen on the carcass
• The pin feathers can be removed using a blunt knife and the hairs by passing the carcass
over a flame of fire
• Cut the head off and the legs where the sheens join the thighs
Evisceration
• Lay the carcass on a clean table and make sure your hands are clean
• Open the skin on the back of the neck and cut the neck bone out
• Loosen the internal organs through the hole created by removing the neck
• Make a hole by cutting the skin across the abdomen in front of the vent and pull out the
internal organs that include the crop, intestines, lungs, heart, gizzard and liver
• The crop and intestines (giblets) should be washed and packed separate from other organs
Dressing
• The carcass should be cleaned thoroughly after removing the internal organs
• The neck skin should be folded back to cover the hole left by neck removal
• Fold the wings to press on the neck skin, hocks should be tucked into the abdomen and
out through the vent
• The carcass should be given a final was then packed before freezing
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FORM 4 AGRICULTURE NOTES
Ruminant livestock production
Cattle
•
•
•
•
•
•
Cattle rearing is a common practice in both communal and commercial farms in
Zimbabwe.
Farmers keep both indigenous and exotic breeds of cattle.
Indigenous breeds are cattle which originated and are kept in Zimbabwe.
Exotic breeds are cattle which originate from other countries and are kept in Zimbabwe.
Cattle production goals can be for meat (beef) or milk (dairy) production.
Production costs are higher for dairy farming than beef production due to the need for
specialised equipment, skilled labour and strict livestock management.
Indigenous cattle breeds
•
•
•
Indigenous cattle breeds are hardy, more adaptable to harsh local climatic conditions and
are tolerant to diseases and parasites.
They are multipurpose i.e. are kept for milk production, meat production and draught
power.
Indigenous cattle breeds found in Zimbabwe are; Mashona, Africander, Tuli and Nguni.
Characteristics of indigenous cattle breeds
Mashona cattle
• Tolerant to hot and harsh climatic conditions (hardy)
• Has a small stature and is resistant to most local and tropical diseases
• They have good fertility rate and do not have problems of dystocia when calving
• Mashona cattle can survive on veld grass and have good feed to meat conversion ratio
• They are horned and their coat colour ranges from black and dark brown, red and mixed
red and white
•
•
•
•
Afrikander cattle
This breed has a hump and is adaptable to high and low temperatures
They can survive low rainfall conditions, are highly resistant to many local and tropical
diseases as well as parasites
Afrikander cattle are good grazers and can survive poor grazing conditions.
Their cows can give birth to large calves without problem.
•
•
Nguni cattle
Body size ranges from small to medium and have a variety of colour patterns which also
include mixed colour patterns.
They are adaptable to hot temperatures common in the Lowveld
The breed is also resistant and tolerant to many local diseases and parasites
•
•
•
Tuli cattle
This is a large breed that has a thick and smooth coat
Their body colour varies but there are no black coloured Tuli cattle
They are adaptable to hot and harsh climatic conditions
•
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FORM 4 AGRICULTURE NOTES
•
•
They can travel for long distance in search of water and good grazing
They are highly fertile and present few problems during calving
Advantages of indigenous breeds of cattle
• They are more resistant to diseases and parasites
• They are adaptable to hot and harsh local climatic conditions
• They are good for providing drought power
• They calve easily
Disadvantages of indigenous breeds of cattle
• They have slow growth rate
• They have small stature and produce small calves
• They do not respond well to pen fattening and often develop laminitis (swollen feet)
• They produce poor beef quality compared to exotic cattle
Exotic cattle breeds
•
•
These are cattle breeds which came from European countries and are kept in Zimbabwe.
Exotic cattle breeds are Hereford, Simmentaler, Aberdeen Angus, Charolais, Brahman
and Sussex.
Characteristics of exotic cattle breeds
Hereford
• This breed originated from England, Herefordshire.
• It has a white coloured face, white patches under the body and under the neck, with a red
body.
• Hereford are large cattle adaptable to a wide range of climatic conditions.
• This breed can survive on poor pasture or grazing conditions.
• Hereford is however susceptible to ophthalmic complications because of the pale pigment
around its eyes.
•
•
•
•
Simmentaler
This breed originated from France.
Coat colour of this cattle breed ranges from dark brown to creamy yellow and white.
It is a dual-purpose breed with excellent beef and milk production.
Simmentaler cows have no or few calving problems.
•
•
•
•
•
Aberdeen Angus
This breed originated from Scotland
It is highly fertile and the cows have a natural good mothering ability.
The breed is naturally polled.
Aberdeen Angus cattle do best in high rainfall areas.
This breed produces high grade beef feeding on natural veld grasses.
•
•
Charolais
This breed originated from South Eastern France.
It has a white colour with pink muzzles and pale hooves.
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FORM 4 AGRICULTURE NOTES
•
•
•
•
Charolais has a coarse fur.
The breed has good feed conversion ratio and superior weight gain.
Have easy calving ability
Have good milk production and are easy to handle
•
•
•
•
Brahman
This breed originated from India.
It is characterised by a hump and is intermediate in size.
It has a short thick glossy hair coat which ranges from light grey, red, to almost black.
Brahman is hardy and adaptable to a wide range of feed and climate.
•
•
•
•
•
•
Sussex
This breed originated from South England.
It is characterised by a smooth dark-red coloured coat with white tail switches.
The breed is medium sized and is fairly easy to handle.
It is highly fertile and has easy calving ability.
Sussex breed has high feed conversion ratio
It is tolerant to drought conditions.
Advantages of exotic cattle breeds
• They have a fast growth rate
• They have a high food to meat conversion ratio therefore are very productive
• They are larger than indigenous cattle breeds
• They produce large calves
Disadvantages of exotic cattle breeds
• They are less hardy and not adaptable to most local climatic conditions
• They are more susceptible to local and tropical diseases and parasites
• They require a close monitoring and management
• They tend to have calving problems
Cattle management practices
•
Success in livestock production depends on the stockmanship qualities of the farmer.
Dehorning
• This is the removal of horn buds.
• Dehorning is done as soon as horns start to emerge.
• Methods of dehorning are:
o use of hot iron
o use of caustic soda
o use of rubber ring
o use of guillotine
• The reasons for dehorning include:
o to reduce fighting or bullying in cattle herds.
o to enable easier transportation of animals.
o to enable easier and safer handling of the cattle.
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FORM 4 AGRICULTURE NOTES
o to reduce space occupied by the animals in handling facilities.
Castration
• This is the removal of the ability of a bull to reproduce.
• The bull will no longer produce sexual hormones and sperms.
• A castrated bull is known as a steer.
• Castration is more easily done on calves than on mature bulls.
• Methods of castration are:
o use of a burdizzo clamp (emasculator)
o rubber ring castration method
o surgical (knife) castration method
o chemical castration
• The reasons for castration are:
o to prevent breeding of inferior breeds.
o to improve meat quality of beef breeds.
o to make draught animals easier to handle.
Animal identification
• This involves marking or numbering of animals.
• It is done for easy identification and management of the animals.
• Methods of animal identification are:
o branding using a hot iron
o placing numbered plastic tags on cattle ears
o ear notching
Deworming (dosing)
• This is the killing of internal parasites.
• Internal parasites affect growth of calves, kids or lambs, damage internal organs and
affect the absorption of nutrients in the small intestine.
• Ruminant animals are dewormed by using Anthelmintics such as ranide, trodax, valbazen
and ripercol.
• The animals are forced to drink the drug using a dosing gun.
Dipping
• This is the killing of external parasites through the use of chemicals called acaricides.
• The most important external parasites of cattle are ticks and tsetse fly.
• These parasites cause irritation to animals and are vectors of diseases.
• Ticks also cause damage to the hide and loss of livestock weight through feeding.
• The methods of dipping are:
o plunging the animals in a dip tank with chemical acaricide
o walking the cattle through a spray race with chemical acaricide
o spraying the animals with the chemical acaricide using a knapsack sprayer
Disease control
• This involves the prevention, control and treatment of diseases.
• Strict hygiene is very important in preventing diseases.
• Clean, fresh water and feeds should be provided to the animals.
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FORM 4 AGRICULTURE NOTES
Supplementary feeding
• This is the supply of additional feeds to the livestock.
• It is done when grazing pasture is poor and when cattle condition starts to deteriorate.
Mating
• This involves the selection of animals to mate in order to produce the best economic
animal breeds.
• The selected animals can be made to mate naturally or the farmer can carry out artificial
insemination.
Record keeping
• Physical and financial records for cattle management are very important tools for
planning, decision making and adjustments in management to maximise productivity.
• One of the important physical record is a stock register.
• A stock register shows the current number of livestock in stock, type of animals, age,
deaths, sales made and purchases of new animals.
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FORM 4 AGRICULTURE NOTES
Animal health
Animal parasites
•
•
A parasite is an organism which feeds on other organisms (host) and cause harmful
effects.
Animal parasites are divided into external and internal parasites
External parasites
•
These attack the host from the outside e.g. ticks, tsetse flies etc.
Ticks
• They feed on animal’s blood and transmit diseases from one animal to another.
• The life cycle of ticks has four stages (egg, larval, nymph and adult)
• Adult female and male tick mate, usually on host.
• The female tick sucks its final blood meal, becomes engorged, drops off and lays eggs on
the ground.
• The eggs produce a six legged larva. High temperature and high humidity promote
hatching of tick eggs.
• The larvae finds a host by climbing up grass and attaching to any passing animal.
• On the host the larva sucks blood, becomes engorged and sheds out its outer skin
(moulting) to become an eight legged nymph.
• The nymph also sucks blood and moults into an adult female or male tick thereby
completing the life cycle.
•
•
•
One-host tick
These are ticks which require a single host (cattle) to finish their life cycle.
Larvae from eggs feed and moult to nymph
The nymph feed and moult to adult on the same host.
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FORM 4 AGRICULTURE NOTES
•
•
•
Prevention/Control of ticks
Dipping and spraying with acaricides. An acaricide is any chemical that is capable of
killing ticks.
Rotational grazing to break the life cycle of ticks.
Burn grazing to control bush encroachment, this will also kill adult ticks, their eggs and
their nymphs.
Internal parasites
•
These attack the host from within e.g. roundworm, tapeworm and liver fluke.
Roundworms (wireworms)
• These have a cylindrical, non-segmented body which is pointed at both ends.
• In an animal they are found in the abomasum.
• They appear red in a freshly-killed animal.
• Roundworms affect ruminant animals especially sheep and goats, in cattle they prevalent
in young ones.
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FORM 4 AGRICULTURE NOTES
•
•
•
•
Symptoms
Loss of weight – animals are thin despite having adequate feed and appetite.
Anaemia – shown by high pulse, high breathing rate and pale or white mucous
membranes.
Prevention/Treatment/Control of roundworms
Rotational grazing
Dosing with Tramisol, Systamex or Trodax
The animal health act
•
This comprises of animal health government regulations which a farmer must be aware of
and abide by.
Notifiable diseases
•
•
•
•
These are highly infectious and cause great economic loss.
They should be reported to the veterinary department or police immediately noticed.
The veterinary department then takes vigorous steps to control the disease.
Notifiable diseases include; foot and mouth, rift valley fever. Anthrax, contagious
abortion, rinderpest, trypanosomiasis and Newcastle.
Permits/Restriction of animal movement
•
•
•
•
•
Animals should be checked for diseases and a movement permit given before they are
moved from one place to another.
An import permit should be obtain before importing animal(s) or animal product.
The animal(s) or animal product should be certified free of certain specified diseases
before import.
The aim of this is to prevent spread of diseases from one region to another or from one
country to another.
Road blocks and boarder ports help to enforce these requirements.
Quarantine
•
•
This is the confinement of animals to a certain area done by the veterinary department for
a given period of time.
This helps to detect suspect animals which might be incubating a disease.
Vaccinations
•
•
This is the injection of animals with a weak pathogen, to prepare the immune system for
infection.
Vaccinations should be carried out regularly especially for notifiable diseases.
Dipping
•
•
Cattle should be dipped regularly.
At least once per week from October to April and once per two weeks from May to
September.
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FORM 4 AGRICULTURE NOTES
Destruction of carcasses
•
All dead animals must be destroyed by burning or deep burial to prevent disease spread.
Animal improvement
•
Animal improvement is done through breeding.
Breeding
•
•
Breeding is the selective mating of male and female animals to produce a hybrid
offspring.
A hybrid offspring has desirable characteristics better than either of its parents.
Importance of breeding
•
•
•
•
•
•
To achieve high milk yield
To have animals with quick growth rate
To have animals with high meat to bone ratio
To improve animals’ resistance to diseases
To improve animals’ adaptability to different climatic conditions
To improve egg production in poultry
Types of breeding
Inbreeding
• It is the mating of closely related animals e.g. father and daughter, mother and son or
brother and sister.
•
•
Advantages
Desirable characteristics are continually passed on in the family
Helps in developing uniformity (homozygosity)
•
•
•
•
Disadvantages
May concentrate undesirable characteristics
Lead to reduced vigour in some traits
Reduces genetic variation
Usually results in deformities
Cross breeding
• Is the mating of pure bred animals from different breeds e.g. Mashona cow and Brahman.
•
•
•
•
Advantages
Offspring produced usually perform better than its parents (hybrid vigour/heterosis)
Most cross breeds are well adapted to different environments
Certain cross breeds are more economical to keep as their ratio of increase in mass to feed
intake is higher than that of pure breeds (they have high food conversion ratio)
Disadvantages
Requires expert knowledge
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FORM 4 AGRICULTURE NOTES
•
Cross breeds do not breed true to type
Test crossing
•
•
This involves the mating of an animal with a known homozygous to establish it genotype.
In order to understand genetic inheritance, genetic diagrams help to follow the
transmission of gametes from parent to offspring e.g. pure breed (homozygous) back
(BB) crossed with another homozygous pure breed with recessive white genes (rr).
Parents
BB
×
bb
Mating
F1 Generation
•
Bb
Bb
Bb
Bb
(All black)
The offsprings hold a dominant gene for black colour B. Self-mating the offspring will
give a ratio of 3 black 1 white
Parents
Bb
×
Bb
Mating
F2 Generation
BB
RODRECK WISEMAN NYAKABAWU
Bb
Bb
bb (3 Black and 1 white)
33
FORM 4 AGRICULTURE NOTES
FARM STRUCTURES AND MACHINERY
Fencing
Anchors
•
•
An anchor is a supporting structure used to reinforce corner posts and straining posts.
Anchors are put at corner posts, straining posts and gate posts to support and make them
resist the pulling force exerted when straining wire strands.
Types of anchors
Double box anchor
•
•
•
•
•
Put at corner and straining posts
It is very strong
Allows straining of wire strands in two directions
It is difficult to construct
It needs skilled workers to construct it.
Box anchor
•
•
•
Put at straining posts
Easy to construct
Allows wire straining in two directions
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FORM 4 AGRICULTURE NOTES
Stay anchor
•
•
Put at straining posts and corner posts
Easy to construct
Double wire anchor
•
•
Put at corner and straining posts
Easy to construct
Gate post anchor
•
•
Put at gates
Makes the gates strong
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FORM 4 AGRICULTURE NOTES
Fencing calculations
Worked example
Calculate the number of straining posts, standards and droppers needed to fenced a 800m
stretch of land if:
1. The distance between straining posts is 400 m.
Answer
800m ÷ 400m = 2
2 + 1 = 3 Straining posts
2. Distance between standards is 14m.
Answer
400m ÷ 14m = 28
28 × 2 = 56
56 – 2 = 54 standards
3. Distance between droppers is 3.5m.
Answer
14m ÷ 3.5m = 4
4 -1 = 3
3 × 56 = 168 droppers
Total materials required = 3 straining posts, 54 standards and 168 droppers
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FORM 4 AGRICULTURE NOTES
Farm buildings
Designs for livestock buildings
•
•
Livestock buildings follow different shapes and designs but should be large enough to
accommodate the animals without overcrowding them.
Before starting any construction, a building plan must be drawn.
A fowl run
•
•
•
•
•
It has a low wall made of bricks with net wire mesh on top.
The walls can be built up to the top to make a storeroom.
The building can be roofed with asbestos or thatch
Low wall prevents cold weather.
Wire mesh improves ventilation and light.
Costs of construction
•
•
•
This is the calculation of materials needed to be used for constructing a building.
Materials needed to construct a building are taken from a building plan.
The list of all materials needed is compiled and then the cost worked out.
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FORM 4 AGRICULTURE NOTES
Farm roads
Road construction materials
Gravel
•
•
•
Small stones whose diameter is >2.0mm in diameter.
It is spread over road surface and compacted to make it firm.
It is easy to firm, drains water easily and is not slippery when wet.
Concrete
•
Used for making culverts, inverts and bridges.
Stones
•
•
Used to make concrete
Can be cemented together to make drains, bolsters and stone pitching.
Sand
•
•
Used to make concrete.
Pulled up by a grader then compacted to make farm roads, used in place of gravel to
minimise cost of construction.
Road construction
Timing
•
•
Farm roads should be constructed during the dry season when labour demand and tractor
operations on farm activities are less.
During the rainy season, tractors and graders can get stuck in the mud.
Pegging
•
•
Start by pegging the width of the road by placing wooden pegs where expect the edges to
be
Use a dumpy level to establish gradient and align the pegs.
Clearing trees and shrubs
•
Clear all trees in the path of the road using mattocks, axes and pruning saw.
Ploughing
•
Plough the cleared part to loosen the soil so that the soil can be easily compacted.
Grading
•
Raise soil from road sides to make a cambered road surface and level.
Surfacing and ramming
•
•
•
Put gravel or laterite on the road surface and spread it over.
Ram the gravel or sand using a tractor or animal drawn rammer.
Ramming compacts the soil and makes the road firm.
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FORM 4 AGRICULTURE NOTES
Maintenance of farm roads
•
•
•
•
•
•
Grading the road up and down to maintain slope and crest.
Opening up silted mitre drains, culverts and inverts.
Strengthening drain bolsters.
Fill in potholes with gravel.
Re-surfacing the road with gravel when necessary.
Planting grass on rad sides to prevent erosion.
Appropriate technology
Shellers
Maize sheller
•
A maize sheller is used to separate maize grains from the cobs
Part
Function
Threshing drum Shelling of grain/kernel
It where the beater bars are attached
Beater bars
Threshing the cobs to separate kernels
Fan
To clean dust and other unwanted materials
Concave plate
Separating the kernels from shelled cobs
Grain chute
Facilitate easy collection of maize grain
Operating principle of a maize sheller
• A maize sheller consists of a feeder tray for cobs with a conveyer belt
• The maize cobs are conveyed into a rotating threshing drum fitted with beater bars
• The cobs are squeezed through a limited space between beater bars and a concaved plate
with holes
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FORM 4 AGRICULTURE NOTES
•
•
•
This removes the maize grains from the cobs
The grains fall through the plate into a chute where air blows through, cleaning off chaff
and impurities
A bag is fitted to the chute to collect the grain for storage
Groundnut sheller
•
A groundnut sheller is used for removing groundnut seeds from the shells.
Part
Function
Base
Main structural frame
Removable grid Acts as base plate that creates limited space to assist the
decorticating bars in splitting the pods releasing the nuts
Handle
Operates the sheller by moving the decorticating bars back and forth
against the removable grid
Decorticating
Squeeze the pods between in and the removable grid splitting the
bars
pods releasing nuts
Hopper box
Holds unshelled nuts during processing
Adjustable
It is adjusted to regulate the amount of groundnuts fed into the
throat slide
sheller during the shelling process
Operating principle of a groundnut sheller
• A groundnut sheller is made up of a feeder metal box where the groundnuts are fed
through
• Beater bars are fitted to an arm which when moved backwards or forwards rub the
groundnuts against a half cylinder wire mesh screen
• This shutter the groundnut pods releasing the seeds to the bottom of the sheller where
they are collected
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FORM 4 AGRICULTURE NOTES
AGRI-BUSINESS
Principles of economics
The law of diminishing returns
•
The law of diminishing returns states that there is a positive relationship between input
applied and the output obtained but only to a certain point where continuous application
of the input on a fixed factor of production will not lead to a corresponding increase in
output.
Example: Diminishing returns on maize yield versus fertilizer application
9
8
MAIZE YIELD (T)
7
6
5
4
3
2
1
0
A
B
C
D
FERTILIZER (50 KG BAGS)
•
•
•
•
•
•
At point A, no fertilizer has been added. A low maize yield is obtained. The crop uses
residual nutrients in the soil.
From A to B, maize output is increasing at an increasing rate due to additional units of
units of fertilizers.
At point B, the increments increase output due to extra units of fertilizers used has
reached a maximum point.
From B to C, the maize output is increasing due to increase in input, but at a decreasing
rate.
At point C, the increase in output due to extra units of fertilizers reaches zero. The maize
output has thus reached its maximum point.
From C to D, the maize output is decreasing. This could be as a result of excessive effects
of the fertilizers.
Implications of the law of diminishing returns
•
•
It helps farmers to know the amount of inputs to buy so as to avoid losses due to
overspending on the production costs and wastage
Helps in maximum utilization of resources
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FORM 4 AGRICULTURE NOTES
Risks and Uncertainties
Risks
•
•
A risk is a danger or a possibility of losing something
It is a problem that a farmer can predict and as a result a farmer can insure against.
Risks faced by farmers
• Fire (on stored crops or dry crop in the field etc.)
• Storm or hail damage (tobacco in field)
• Drought
• Excessive rains
• Theft
• Pest outbreak
• Disease outbreak
• Farmer’s health
• Rise in fertilizer (cost which could not be predicted)
Uncertainties
•
•
An uncertainty is an unforeseen threat to farming business
It is a problem that farmers cannot predict and as a result cannot be ensured against.
Uncertainties faced by farmers
• Change in demand for a good
• Change in government policy
• Unavailability of labour
• Price changes or fluctuation
• Transport reliability
• Technological changes
Guarding against risks and uncertainties
•
•
•
•
•
•
•
Insuring crops against failures
Diversify (running several enterprises at once)
Choose the most certain or reliable enterprise
Be flexible (be ready to change plans)
Ration inputs
Use records and financial information
Producing crops on contract
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FORM 4 AGRICULTURE NOTES
Decision making
•
This refers to the choosing and deciding on how resources are best used or allocated on
the farm to increase outputs and profits on the farm.
Importance of decision making
•
•
•
•
Allows effective allocation and utilization of resources
Allows for the best choice of enterprise to undertake
Helps in avoiding losses
Helps in improving performance on farming activities being undertaken
Economic factors influencing decision making
•
•
•
•
Capital availability
Availability of labour
Availability of land
Compatibility of the decision with the available resources
Steps to follow when making decisions on a farm
1.
2.
3.
4.
5.
6.
7.
Identify the problem
Identify alternatives
Gather information
Analyse alternatives
Implementing the decision
Monitoring the results
Accept responsibility
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FORM 4 AGRICULTURE NOTES
Marketing
Marketing legislation
•
•
This involves government intervention in the marketing of agricultural products.
The government regulates the marketing of agricultural products in controlled markets
through government instruments
Government instruments
•
•
These are laws, policies, statutory instruments and rules used by the government to
regulate marketing of agricultural products
These include:
o improving efficiency of agricultural marketing system
o market pricing
o marketing infrastructure development
o marketing information, research and intelligence
o marketing institutional and regulatory environment
o value addition
Reasons for marketing legislation
•
•
•
•
•
To develop a competitive and efficient agricultural marketing system
To ensure competitive and viable prices for all agricultural commodities
To develop complex and functional agricultural marketing infrastructure
To avail adequate, quality and timeous agricultural marketing information to all
agricultural actors
To enhance the processing of agricultural products for the purpose of value addition
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