Environmental Factors Affecting Agricultural Production – SS1 Agricultural Science Lesson Note (Second Term)

Environmental factors affecting agricultural production are the conditions around crops and animals that influence how well they grow and yield. They fall into three groups: climatic factors (rainfall, temperature, sunlight, wind and relative humidity), biotic factors (living organisms such as pests, parasites and weeds) and edaphic factors (soil conditions such as pH, texture and structure).

Behavioural objectives

By the end of the lesson, students should be able to:

1. name the three groups of environmental factors affecting agricultural production;
2. define climate, rainfall and temperature;
3. state the effects of rainfall, temperature, sunlight, wind and relative humidity on crops and livestock;
4. describe the biotic factors, including predators, parasites, pests, diseases and weeds;
5. define soil pH, soil texture and soil structure and state their importance.

What are the groups of environmental factors?

There are three groups of environmental factors: climatic, biotic and edaphic.

What are the climatic factors?

Climate is the average weather condition of a place measured over a long period.

• Factors: rainfall, relative humidity, temperature, light, wind and pressure.
• Effect on farming: climate decides which crops and animals suit an area.
• Example: thick evergreen forest grows in the high-rainfall south, while grassland vegetation is found in the drier north.

What is rainfall?

Rainfall is the amount and distribution of water precipitation within a given time in a given area.

How is rainfall distributed in Nigeria?

1. West Africa has high temperature throughout the year.
2. Rain comes from the south-west wind blowing from the Atlantic Ocean.
3. The wind drops water as it moves inland, so rainfall decreases as we move away from the coast.
4. By the time the wind reaches the north, little moisture is left, so rainfall there is low.

• Livestock in the humid south: little animal rearing is done because high humidity exposes animals to tsetse fly, which carries trypanosomiasis.
• Trypanosomiasis-resistant animals: N’dama and Muturu cattle, dwarf sheep and goats, and poultry.

What are the effects of rainfall?

• Distribution: it determines where crops and animals are found.
• Nutrients: it dissolves soil nutrients so plants can take them up.
• Germination: water is needed for seeds to germinate.
• Vegetation: it determines the type of vegetation in an area.
• Excess rain: it leaches nutrients and causes soil erosion.
• Too little rain: it causes crop failure and poor yield.

What is temperature?

Temperature is the degree of hotness or coolness of a place, a measure of the heat energy a body contains.

• Variation: temperature changes from the coast to the extreme north.
• Dry season: the coast is not as hot as the extreme north.

What are the effects of temperature?

• Distribution: it affects where crops and animals can live.
• Germination: seeds need a suitable temperature to germinate.
• Dormancy: unfavourable temperature may keep seeds dormant.
• Crops: high temperature may cause premature dropping of fruits.
• Livestock: high temperature reduces performance and can cause sudden death from heat stress.

What are the effects of sunlight?

Sunlight is the light energy from the sun that plants and animals depend on.

• Photosynthesis: plants need it to make food.
• Poultry: it affects the rate of egg production.
• Water loss: it affects evapotranspiration.

What are the effects of wind?

Wind is air in motion.

• Erosion: high wind may cause wind erosion.
• Dispersal: it carries seeds and fruits to new places.
• Pollination and disease: it can aid pollination and spread disease.
• Seasons: it helps distribute rainfall and bring changes between rainy and dry seasons.
• Damage: high wind velocity damages crops.

What are the effects of relative humidity?

Relative humidity is the amount of water vapour in the air compared with the most the air can hold at that temperature, shown as a percentage.

• Rain: moisture in the air leads to the formation of rain.
• Performance: it affects the performance of crops and animals.
• Poultry: high humidity causes mouldy feed and wet litter.
• Livestock: high humidity with high temperature causes heat stress, and very low humidity causes dehydration.
• Pests: it determines the type of pests found in an area.
• Disease: high relative humidity encourages the growth of disease pathogens.

What are the biotic factors affecting crop and animal production?

Biotic factors are the living organisms that affect crops and animals.

The main biotic factors are predators, parasites, soil organisms, pests, diseases, symbiotic organisms and weeds.

What are predators?

Predators are living organisms that prey or feed on other organisms.

• Examples: birds, rodents and insects.
• Beneficial predators: some control harmful pests of crops and animals.
• Destructive predators: some feed on farm animals, e.g. hawks feeding on chicks.

What are parasites?

A parasite is an organism that lives on or in another living organism, the host, and feeds on it.

• Harm: a parasite often harms its host by causing disease or death.

What are the types of parasites?

There are two types of parasites: endoparasites and ectoparasites.

• Endoparasites: live inside the body of the host, e.g. liver fluke, tapeworm and roundworm (ascaris).
• Ectoparasites: live outside, on the host, e.g. ticks, lice, mites, insect bugs and fleas.

What are soil organisms?

Soil organisms are living things that spend all or part of their life in the soil.

• Micro-organisms: very small organisms such as bacteria, fungi and viruses.
• Macro-organisms: larger organisms such as rodents, termites and centipedes.
• Harmful ones: some bacteria and fungi cause disease.
• Aeration: some aerate the soil and so improve fertility.
• Nitrogen fixation: root nodule bacteria fix nitrogen for plants and soil.
• Decomposition: some break down plant and animal material to form humus.

What are pests?

Pests are organisms that damage or destroy crops in the field or in stores.

• Examples: insects, rodents, birds and some animals such as monkeys.
• Yield: they reduce the yield of crops and animals and so reduce the farmer’s income.
• Vectors: some carry diseases.
• Cost: controlling them raises the cost of production.

What are diseases?

Disease is a departure from the normal state of health in plants or animals.

• Cause: pathogens such as viruses, bacteria, fungi and protozoa.
• Yield: diseases reduce yield and can kill plants and animals.
• Cost: control raises the cost of production and cuts the farmer’s income.

What is symbiosis?

Symbiosis is a close living relationship between two different organisms, and mutualism is the type in which both benefit.

• Example: termites and the protozoa in their guts.
• Termites give: protection to the protozoa.
• Protozoa give: help in breaking down and digesting the termites’ food.

What are weeds?

Weeds are plants growing where they are not wanted, which compete with crops.

• Competition: they compete with crops for space, water, nutrients and sunlight.
• Hosts: some harbour pests and diseases.
• Yield and cost: they reduce yield, and control raises the cost of production.

What are the edaphic factors?

Edaphic factors are the factors that come from the soil, such as its pH, texture and structure.

What is soil pH?

Soil pH is the degree of acidity or alkalinity of the soil.

• Scale: a pH below 7 is acidic, 7 is neutral and above 7 is alkaline.
• Plant growth: it affects the growth of plants.
• Nutrients: it affects how available soil nutrients are to plants.
• Micro-organisms: it affects which micro-organisms live in the soil.

What is soil texture?

Soil texture is the fineness or coarseness of a soil, based on the sizes of its particles.

• Soil type: it determines the type of soil in an area, such as sandy or clay soil.
• Fertility: it determines the level of soil fertility.
• Crops: it determines the type of crops that can be grown.
• Loss of soil: it affects the level of leaching and erosion.

What is soil structure?

Soil structure is the way individual soil particles are packed or arranged together.

• Fertility: it determines the fertility of the soil.
• Water: it determines the water-retaining capacity.
• Aeration: it determines how well air moves in the soil.
• Micro-organisms: it determines the level of micro-organisms.

Evaluation

1. What is climate?
2. Discuss the importance of rainfall in agriculture.
3. What is temperature?
4. State the difference between endoparasites and ectoparasites, with one example of each.
5. List three effects of weeds on crop production.

Assignment

Define soil pH, soil texture and soil structure, and state one importance of each.