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Form 1 Agriculture Notes on Factors Influencing Agriculture

Grade/Class: Form 1

Subject: Agriculture

Term: Select Term

Document Type: PDF


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These factors can be divided into:
- Human factors
- Biotic factors
- Climatic factors
- Edaphic factors

Human Factors
a.) Level of Education and Technology
- More yields is associated with high level of education and technology.
- Poor level education and technology causes sluggish development in all farming activities.
b.) Economy
- Collapse of co-operative movements and factories have affected the sale of farm produce such as milk, sugar and cotton.
- Liberalization of the economy and world trade has led to dumping of cheaply
produced and cheaply imported goods that have flooded our local
c.) Government policy
- This is the enactment of laws which govern production, marketing and distribution of agricultural products.
- They may include the following:
i. Heavy taxation of imports to protect local industries.
ii. Subsidizing the growing of locally produced commodities.
iii. Quality control to ensure production of high quality goods.
iv. Conservation of natural resources
v. Stepping up the control of diseases and parasites that affect crops and livestock.
d.) Transport and communication
- Means of transport and communication affect agriculture in the following ways.
i. Agricultural goods should be taken from production areas to the consumers cheaply and efficiently.
ii. The use of electronic media as a means of communication helps access a wider market.
e.) Cultural Practices and Religious Beliefs
- They affect what people produce and consume
- Some pastoral communities rely on meat and milk while other communities rely on
f.) Market Forces
- Market forces affecting agriculture are demand and supply.
- When the supply is high, prices of commodities go down.
- This increases the demand for the commodities.
- As demand increases the quantities of commodities supplied in the market decreases. This in turn increases the price of the commodities.
g.) Health (HIV /AIDS)
- Shortage of farm labour due to bad health/death.
- Low supply of farm produce due to loss of market.
- Low purchasing power to buy agricultural input/lack of capital by the government and NGOs to provide credit to farmers.
- Lack of motivation to invest in agriculture.
- Less time spent on farming activities as people cater for the sick.

Biotic factors
- Nitrogen fixing bacteria- convert atmospheric nitrogen to nitrates for plant uptake.
- Pollinators – transfer pollen grains from the anther of a flower to the stigma of the same flower or different flower.
- Decomposers – organisms which breakdown organic plant and animal remains to release nutrients for plant.
- Pests – attack crops by eating plant parts, piercing and sucking sap and introduce / spread disease causing microorganisms.
- Pathogens – they cause crop diseases.
- Predators-Reduce pest population.
- Weeds- Compete for nutrients, space, light, moisture and spread pests and diseases

Climatic factors
a.) Temperature
This is the degree of hotness or coldness measured in oC. The range within which plants thrive is called the cardinal range; plants do best at optimum range which is a narrow range within the cardinal range of temperature
Temperature affects agriculture in the following ways
i) Increases incidences of some pests/parasite and diseases
ii) Improves quality of certain crops e.g. fruits, pineapples, papaws’
iii) Lowers quality of certain crops e.g. pyrethrum
iv) Increases rate of evapotranspiration/wilting in plants
v) Increases rate of growth for early maturity in crops
vi) Limits distribution of exotic livestock breeds
vii) Lowers production in livestock
viii) Influences design of farm buildings and structures
ix) Lowers labour productivity
b.) Wind
- Increase rate of evaporation
- Agent of seed dispersal
- Increases spread of disease and pests
- Agent of soil pollination
- Bring rain – bearing clouds
c.) Rainfall
- Main source of water required by all living processes.
- It must be adequate to sustain both animal and plant life.
- Lack of sufficient water in plant results in plant wilting, while in animal it causes dehydration.
Five aspects of rainfall that a farmer may consider when deciding on what crop to grow in an area.
i. Rainfall reliability
ii. Amount of rainfall
iii. Rainfall distribution
iv. Rainfall intensity
d.) Light
- Light is essential to plants as it provides the energy required for photosynthesis?
The three important aspect of light in crop growth.
i. Light intensity
- This is the strength with which the light is harnessed by chlorophyll for the purpose of photosynthesis.
ii. Light duration
- This refers to the period during which light is available
iii. Light wavelength
- It makes natural rather than artificial light more suitable for plant growth.
e.) Relative Humidity
- This is the amount of water vapour held by air at a given temperature, compared to what it would hold when saturated.
- At high relative humidity, the rate of evapotranspiration is low.

Edaphic/soil factors
Soil is the natural material on the uppermost layer of the earth’s crust which supports plants growth.
Soil formation
Soil is formed through weathering process.
Weathering – breakdown and alteration of the parent rock near the earth’s surface to
produce what is more in equilibrium with the newly – imposed physic-chemical conditions.
Weathering process is brought about by physical, biological and chemical agencies. These processes are influenced by:
- Climate
- Parent materials
- Living organisms
- Topography
- Time
i. Physical Agents of weathering
- These include wind, water, moving ice and temperature.
- Strong winds carry materials which hit against each other making surfaces of the materials break off into smaller fragments.
- Raindrops hit the ground with some force eroding soil surfaces.
- In arid and semi- arid regions, the temperatures are very high during the day. This makes the rocks expand starting from the outside to the inside.
- During the night, temperatures drop. Thus the surface contracts faster than the inside.
- This unequal expansion and contraction of the rocks causes the outside part of the rocks to flake off.
- Physical/mechanical weathering in time mainly causes the disintegration of rocks without any chemical changes being involved.
ii. Biological agents of weathering
- Movements of animals in large numbers causes weathering
- Decomposition of plants and animals remains by soil micro-organism.
- Physical breaking of rocks by roots of higher plants.
- Man’s activities e.g. cultivation, mining and road construction.
- Mixing up of soil burrowing animals e.g. earth worms and termites
iii. Chemical weathering
- This is the decay or decomposition of rocks.
- It involves various chemical reactions which take place between rock minerals, water and certain atmospheric gases like oxygen and carbon dioxide.
- Mechanical process open up the rock allowing water to enter.
- As the rain falls through the atmosphere, it dissolves some carbon dioxide forming very weak carbonic acid.
- Over a period of time, this acid reacts with the mineral particles of the rocks particular calcium carbonate, causing decomposition.
- The chemical reaction is summarized as follows: Rain water + carbon dioxide = weak carbonic acid. H20 + CO2 = H2CO3
Weak carbonic acid + limestone = calcium bicarbonate H2CO3 + CaCO3 = Ca (HCO3)2
- Calcium bicarbonate formed by this reaction is soluble in water and the process effectively dissolves the rocks.
- Oxygen reacts with many elements including iron from Olivine rocks forming ferrous and ferric oxides, which produce red soils.
Factors Influencing Soil Formation
Parental Rock material
This is the material from which the soil has developed and can vary from solid rock to deposits like alluvium and boulder clay. The parent material can influence the soil in a number of ways:
i. Colour
ii. texture
iii. structure
iv. mineral composition
v. permeability/drainage
Climate governs the rate and type of soil formation and is also the main determinant of vegetation distribution.
Soil climate has two major components; moisture (precipitation) and temperature, influencing evaporation. When precipitation exceeds evaporation, leaching of the soil will occur.
Temperature determines the rate of reactions; chemical and biological decay and so has an influence on weathering and humification.
Other climatic factors include: rainfall, sunshine, relative humidity and wind.
Wind acts as a transport agent and carries the weathered materials from one place to another.
This is the shape of the land in relation to the underlying rock of the earth’s surface.
It may hasten or delay the effects of climate on soil formation.
Factors such as elevation, slope and degree of exposure or shelter may influence the degree of soil erosion, which lead to shallow or deep soils.
The slop affects the depth of the soil and kind of vegetation growing in an area.
Topography influences the movement of products of weathering which consists of soluble substances and solid soils particles.
Topography through its influence on drainage, may indirectly influence the type of clay minerals found in soils.
The length of time over which the soil – forming processes have been in action affects the age of the soil.
Where the soil-forming process have taken place over a long period, deep mature soils can be found ,provided other factors such as topography, nature of parent materials, vegetation and climate favors the development.
Where erosion has been severe because of topography, there is tendency for the soil to remain shallow and youthful with a poorly differentiated profile.
Soil profile
This is the vertical arrangement of various soil layers or horizons.
The soil horizons down the profile are named in order: topsoil, subsoil, and substratum and parent rock.
They can also be named as horizon A, B, C and D respectively.
i. Superficial layer
– this is a thin layer consisting of dry decaying and decayed organic matter covering the soil surface.
ii. Topsoil (Horizon A)
– This is the uppermost soil layer which lies beneath the superficial layer. - It is darker than the other layers due to its high humus content.
- It is well aerated and contains active living organism which break down and decompose organic matter into humus.
- Most of the plant roots are found here.
- It is well drained and contains most of the plant nutrients.
iii. Sub- soil ( horizon B)
- Found immediately below the top soil.
- More compact and less aerated than the top soil.
- Impermeable layer called hardpan may be found in some layers of the subsoil.
- This impedes drainage and may prevent root penetration.
- Clay deposits due to downward movement of clay colloids.
- Sometimes minerals are leached from the topsoil and they accumulate here, hence the subsoil layer is referred to as layer of accumulation.
iv. Substratum/weathered rock (horizon C)
- This layer is found beneath the subsoil and is made of partly weathered rock with no humus.
- It is hard and therefore, impermeable to water.
- Roots of big trees may reach this area this layer and draw water from it during the dry season.
v. Parent rocks/bedrock ( Horizon D)
- This layer is found below the weathered rock.
- Soil is formed from this rock.
- Ponds of water are often found in this rock. A transitional zone
- Found between any two bordering soil layers, whereby one layer gradually mergers into the next one in the series.
Soil constituents
Soil is made up of the following components:
- Mineral matter
- Organic matter
- Air
- Water
- Living organisms


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