CONTENT:

Climate

Parent materials

Topography

Biotic factors

Time

Factors of soil formation

The factors that control soil formation include: climate, parent materials, topography, biotic factors (living organisms), and time.

Climate: Climate refers to the average weather conditions of a place measured over a long time. Elements of climate include sunlight, temperature, wind, relative humidity, rainfall, and pressure.

Rainfall: Running water as a result of rainfall causes the gradual wearing away of rocks during erosion, giving rise to the soil. The impact of raindrops can also break rocks to form soil.

Temperature: The alternate heating and cooling of rocks gives rise to continuous expansion and contraction of rocks. This causes cracks in the rock and, over time, leads to the formation of soil.

Wind: High wind velocity, most especially in desert regions, carries tiny rocks which hit themselves or other rocks, leading to the breakdown of rocks into tiny pieces to form soil.

 Pressure: High pressure in a hanging rock may cause the rock to fall and break into tiny pieces to form soil.

Evaluation

1. What is climate?

2. List five elements of climate

Parental materials: The physical and chemical features of parent materials determine the type of soil that can be obtained from such material. Parent of predominantly quartz mineral gives rise to sandy soil, while that of micas and feldspars gives rise to clayey soil.

Topography: Soil erosion is more pronounced in a sloped area than on flat land. Wind or water easily wears away the soil and rock surfaces in a sloppy area. As the rock particles are washed down to the bottom of the slope, the particles further break up into smaller particles due to the combined effect of
other processes of weathering.

Evaluation

1. Describe how parent materials affect soil formation.

2. What is topography?

Biotic factors (living organisms)

The action of microorganisms, plants, and animals plays an active part in the rock formation.

Termites and earthworms mix the minerals and organic matter, resulting in the formation of soil. The burrowing activities of earthworms and crickets permit the air and water movement in the soil, which reacts with the rock to cause breakdown into the soil.

Activities of man during the tillage operation break the rock into tiny pieces to form soil. Penetration of plant roots causes weathering of rocks. The decay of falling leaves of the trees, with the aid of bacteria, results in the formation of
humus-rich in plant food.

 Evaluation

1. List five biotic factors of soil formation

2. Describe briefly the role of vegetation in soil formation

Time: Time also plays an important role in soil formation. It takes a long time for mature soil to be formed. It takes time for small pieces of rock to disintegrate into grains of soil. It also takes a long time for plants to decay and become part of the soil.

General evaluation

1. What are the factors of soil formation?

2. What are the elements of climate

3. List five biotic factors that cause soil formation

4. List five biotic factors of soil formation

5. Describe briefly the role of vegetation in soil formation

Theory

1. Mention two major elements of climate

2. Discuss three ways by which vegetation affects soil formation.

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