Factors of Soil Formation

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Welcome to class! 

In today’s class, we will be talking about the factors of soil formation. Enjoy the class!

Factors of Soil Formation

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 condition 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 from rainfall causes gradual wearing away of rocks during erosion giving rise to the soil. Impact of raindrops can also break rocks to form soil.

• Temperature:

The alternate heating and cooling of rocks give rise to continuous expansion and contraction of rocks. This causes cracks in the rock and over time lead 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 give rise to clayey soil.

• Topography:

Soil erosion is more pronounced in a sloppy area than 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.

• Termite and earthworms mix the minerals and organic matter resulting in the formation of soil.
• The burrowing activities of earthworm 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 tillage operation break the rock into tiny pieces to form soil.
• Penetration of plant roots causes weathering of rocks.
• The decaying 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 rocks 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 affect soil formation.

 

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