Meaning and Importance of Agricultural Ecology – SS1 Agricultural Science Lesson Note (First Term)

Agricultural ecology is the study of crop plants and farm animals in relation to one another and to their environment.

Behavioural objectives

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

1. define agricultural ecology and ecosystem;
2. distinguish between autecology and synecology;
3. list the biotic and abiotic components of the farm ecosystem;
4. state the importance of agricultural ecology;
5. describe the interaction among the components of the ecosystem in mono-cropping, mixed cropping and mixed farming.

What is agricultural ecology?

Agricultural ecology is the study of how crop plants and farm animals relate to one another and to the environment in which they live.

• Origin of the word: ecology comes from the Greek words “oikos” (home or dwelling place) and “logos” (study).
• Meaning: it is the study of the “home” of crops and farm animals.
• Scope: it covers living organisms, their relationships and the non-living factors around them.

What are the branches of agricultural ecology?

There are two branches of agricultural ecology: autecology and synecology.

Autecology

Autecology is the study of one organism, or one species, and its environment.

• Example: the study of a single cow and its environment.

Synecology

Synecology is the study of the relationships between groups of organisms or species living together in an area.

• Example: the study of different fishes in a fish pond in relation to their aquatic environment.

Autecology compared with synecology

What is an ecosystem?

An ecosystem is a community of living things (crop plants and farm animals) functioning together with their non-living environment.

• Living factors: plants and animals on the farm.
• Non-living factors: soil, water, air, sunlight and similar things.
• Interaction: the living and non-living factors affect one another all the time.

What are the components of the farm ecosystem?

There are two main components of the farm ecosystem: biotic (living) and abiotic (non-living).

Biotic components

Biotic components are the living things in the ecosystem, that is, crop plants and farm animals, grouped as autotrophs and heterotrophs.

• Autotrophs (producers): organisms that make their own food from simple inorganic substances, mainly by photosynthesis. Crop plants such as maize and cassava are autotrophs.
• Heterotrophs (consumers): organisms that cannot make their own food and depend directly or indirectly on plants for it. Farm animals are heterotrophs.

Groups of heterotrophs on the farm

• Herbivores (primary consumers): animals that feed directly on green plants, such as cattle, sheep, goats and rabbits.
• Carnivores: animals that feed on other animals, such as cats feeding on rats.
• Omnivores: animals that feed on both plants and animals, such as pigs and chickens.
• Decomposers: bacteria and fungi that break down dead plants and animals and return nutrients to the soil.

Autotrophs compared with heterotrophs

Abiotic components

Abiotic components are the non-living things in the ecosystem, and there are four groups.

• Climatic factors: rainfall, temperature, wind, humidity and sunlight.
• Inorganic materials and nutrients: carbon dioxide, oxygen, nitrogen, calcium and phosphorus.
• Edaphic factors: soils, rocks and topography (the shape and slope of the land).
• Other factors: dust, storm, fire and water.

Why is agricultural ecology important?

Agricultural ecology is important because it helps farmers understand how crops, animals and the environment affect one another.

• Choice of crops and animals: it helps farmers pick those suited to the climate and soil of an area.
• Higher yield: knowing the needs of crops and animals helps farmers plan good cropping systems.
• Pest and disease control: it shows how pests, diseases and their hosts live, so they can be controlled.
• Soil fertility: it explains how nutrients move between soil, plants and animals, so fertility can be kept up.
• Conservation: it guides the careful use of soil, water and other natural resources.
• Planning: it helps farmers prepare for the effects of weather and climate on the farm.

How do the components of the agro-ecosystem interact in farm settings?

The components of the agro-ecosystem interact through the exchange of nutrients, water, gases and food between living and non-living things.

Mono-cropping (sole cropping)

Mono-cropping is a system of growing one type of crop on a farmland at a particular time.

• Examples: oil palm farms, kola nut farms and maize farms.

Interactions between biotic and abiotic factors:

1. Crop plants absorb nutrients from the soil to grow.
2. Crop plants absorb water to grow and produce fruits.
3. Crop plants take in carbon dioxide from the air to carry out photosynthesis.

Mixed cropping

Mixed cropping is a system of growing two or more crops on the same piece of land at the same time.

• Example: maize, cassava and cowpea grown together on one farmland.

Interactions among the components:

1. Crops like cowpea add nutrients to the soil.
2. Crops like cassava take nutrients from the soil to grow and produce tubers.
3. Leaves of all the crops fall and decay, and soil microorganisms decompose them to add nutrients to the soil.

Mixed farming

Mixed farming is the growing of crops and the rearing of animals at the same time on the same piece of farmland.

• Layout: one part of the farm is used for crops, and the other part for grasses and livestock.

Interactions among the components:

1. Grasses and crop remains serve as food for the animals.
2. Animal dung and droppings are used as organic manure to improve soil fertility for the crops.
3. Crops such as cowpea, and crop residues, decay and release nutrients to the soil.

Cropping systems compared

Evaluation

1. State the origin and meaning of the word “ecology”.
2. Distinguish between autecology and synecology, giving one example of each.
3. Name the two main components of the farm ecosystem.
4. Differentiate between autotrophs and heterotrophs.
5. Give two examples of edaphic factors.

Assignment

Write short notes on how the components of the ecosystem interact in mixed cropping and in mixed farming, giving three points for each.