AGRICULTURAL ECOLOGY

Agricultural ecology can simply be defined as the study of crop plants and farm animals in relation to their environment. Ecology is derived from a Greek word Oikos which means home or dwelling place. In other words, agricultural ecology can be defined as a field of study which deals with the relationship of living organisms with one another and with the environment in which they live.

Agricultural ecology is divided into two main branches:

• Autecology: Autecology is concerned with the study of an individual organism, or a single species of organism and its environment for example, the study of a single cattle and its environment.
• Synecology: Synecology is concerned with the study of the inter-relationships between groups of organisms or species of organisms living together in an area for example, the study of different fishes in a fish pond in relation to their aquatic environment.

Ecosystem

An ecosystem refers to a community of crop plants and farm animals functioning together with their non-living environment. In other words, ecosystem consists of living factors (plants and animals) interacting with the nonliving factors in a farm environment. It should be noted that a farm ecosystem is a natural unit in which there is an interaction between all living organisms (called biotic factors) and non-living organisms (called abiotic factors ) within a farm environment or habitat.

COMPONENTS OF FARM ECOSYSTEM

The farm ecosystem is made up of two main components. These are the biotic (living) components and the abiotic (nonliving) components.

1) Biotic components: The biotic components include the living things (crop plants and farm animals). The biotic components can be grouped into two classes. These are heterotrophism and autotrophism

• Autotrophism: This is a group of organisms which can use sunlight or chemicals to manufacture their food from inorganic substance during the process of photosynthesis. In other words, autotrophs are organisms mainly crop plants which are capable of synthesizing their own food hence they are called producers. Producers are green plants or autotrophs which traps the energy of sunlight, radiant energy or solar energy and converts it to chemical energy in order to form organic compounds during photosynthesis using carbon dioxide and water or simple inorganic substance as raw materials. Producers or autotrophs provide food for the other organisms in the farm.
• Heterotrophism: Heterotrophism is a group of organisms mainly farm animals, which can not manufacture their own food but depend directly or indirectly on plants for their food, hence they are called consumers. Farm animals that feed directly on green plants (producers) are called herbivores or primary consumers e.g. cattle, sheep, goat and rabbit while animals or organisms that feed on the primary consumers are called carnivores or secondary consumers. Animals that feed on the secondary consumers are called tertiary consumers. Heterotrophs includes all farm animals, fungi and some bacteria.

2) Abiotic components: The abiotic components of an ecosystem include the non-living things which are:

• Climatic factors like temperature, wind, humidity, sunlight and rainfall.
• Inorganic materials and nutrients such as carbon dioxide, oxygen, nitrogen, calcium and phosphorus.
• Edaphic factors like soils, rocks, topography.
• Other factors like dust, storm, fire and water.

GENERAL INTERACTION AMONG THE COMPONENTS OF ECOSYSTEM

There is a unique interaction among the various components of an ecosystem. Green crop plants use carbon dioxide, water and chlorophyll in the presence of sunlight to produce carbohydrate or starch. Farm animals feed on these carbohydrates or plants and release carbon dioxide for crop plant to take in. Micro-organisms and other decomposers break down dead plants and animal dungs to release nutrients to the soil. These nutrients are absorbed by plants for use in food production. Crop plants gives out oxygen during photosynthesis which is used by animals for their normal respiration.

INTERACTIONS AMONG THE COMPONENTS OF AGRO-ECOSYSTEM IN SOME FARM SETTINGS

a) In Mono or Sole Cropping System

Mono cropping is a system of cropping where one type crop is grown on a farm or the same piece of land at the same time. Mono cropping is usually practiced on large scale farms, where crops such as oil palm, cocoa, kolanut, rubber, rice, maize, etc are grown.

The interaction between the biotic and the abiotic factors in the environment are as follows:

1. Crop plants absorbs nutrients from the soil to grown.
2. Crop plants also absorb water to grow and produce fruits.
3. Crop plants also absorbs carbon dioxide from the air to carry out photosynthesis.
4. Crop residues decay and with the aid of soil micro-organisms release nutrients to the soil.
5. Some organisms in the soil like earthworms, rodents also aid water percolation.
6. Crop plants also release oxygen to the atmosphere during respiration.

b) In Mixed Cropping System

Mixed cropping system is a system of cropping which involves the growing of two or more crops on the same piece of land at the same time, during the same growing season. The crops are mixed together on the same piece of land. Crops like maize, cassava, cowpea etc can be cultivated at the same time on the same piece of land.

The interaction between the biotic and the abiotic factors in the environment are as follows:

1. Crops like cowpea is capable of adding nutrients to the soil.
2. Crop plants like cassava obtain nutrients from the soil to grow and produce fruits.
3. Carbon dioxide from the air is absorbed by the crop plants to manufacture their food through the process of photosynthesis.
4. Oxygen is also released to the atmosphere by the crop plants during photosynthesis.
5. The leaves of all the crops which fall on the ground decayed and add nutrients to the soil through decomposition by soil micro organisms.
6. Farm animals can feed on these crops and release feaces or dung on the ground which later decay to release nutrients to the soil.
7. Crop plants also release carbondioxide into the atmosphere during respiration.

c) In mixed farming

Mixed farming involves the cultivation of crops and rearing of animals simultaneously on the same piece of land or farm. The farm may be divided into two parts: one part for growing crops and the other part for growing of grasses and keeping of livestock.

Interaction between the biotic and abiotic factors in the environment are as follows:

1. The grasses or the remains of crop serves as food for the animals.
2. The animal dungs and droppings are used as organic manure to improve the soil fertility for the crops.
3. Both animals and crops releases carbon dioxide to the atmosphere during respiration.
4. Some crops like cowpea and crop residue may decay to releases nutrients to the soil
5. Crop plants absorbs soil nutrients and water from the soil for growth and production.
6. Crop plants can also release oxygen to atmosphere during the process of photosynthesis
7. Crop plants also make use of sunlight in the environment to make the food through the process of photosynthesis.

d) In Fish Pond

Fish pond is an aquatic environment where fishes live, grow, produce and harvested for food and other commercial purposes.

The interaction between the biotic and abiotic factors in the the aquatic environment include the following:

1. The fishes feed on planktons, in the water as their sources of food.
2. The death of some fishes serves as manure for the microscopic plants (planktons) in the water.
3. Both planktons and fishes release carbondioxide to the aquatic habitat which aid photosynthesis by the planktons.
4. The planktons in the water make use of carbon dioxide and water to make their food and releases oxygen to the environment which aid respiration in water.
5. The planktons also make use of sunlight during photosynthesis to manufacture their food.
6. Fish dungs or dropping also provide a source of nutrients to the planktons in the water.

e) In The Forest Or Savanna

The forest or the savanna are large expanse of land containing varieties of plants and animals living and interacting together in a terrestrial environment.

Interaction between the biotic and abiotic factors in a terrestrial (forest or savanna) environment are as follows:

1. Animals feed on plants and fruits to obtain their food.
2. Animal dungs and droppings can serve as nutrients to the soil.
3. Plants obtain the nutrients and water from the soil to enable them prepare their food.
4. Plants and animals also respire to release carbon dioxide to the environment which is used by plants to manufacture their food.
5. Sunlight from the atmosphere is also used by green plants to manufacture their food during photosynthesis.
6. Plants generally releases oxygen into the environment during photosynthesis.