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 period. 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 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 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

PARENT MATERIAL

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

TOPOGRAPHY

Soil erosion is more pronounced in sloping areas 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 rock formation.

1. Termites and earthworms mix the minerals and organic matter, resulting in the formation of soil.
2. The burrowing activities of earthworms and crickets permit the air and water movement in the soil, which reacts with rock to cause breakdown into soil.
3. Activities of man during the tillage operation break rock into tiny pieces to form soil.
4. Penetration of plant roots causes weathering of rocks.
5. 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 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

WEEKEND ASSIGNMENT

1. The average weather condition of a place over some time is referred to as A. Climate, B. Vegetation, C. Biotic facto,r D. Humidity
2. Which of these is not a climatic factor of soil formation? A. Temperature B. Wind C. Humidity D. Erosion

3. The following are biotic factors influencing soil formation, except A. Termites activities B. soil pH C. Microorganism  D. Tillage activities
4. The shape of the ground about the underlying rock of the earth surface is known as _____  A. slope         B. disintegration C. topography D. weathering
5. Which of the following is not a factor of soil formation? A. Topography B. Vegetation  C. Parent material  D. Weathering

THEORY

1. Mention two major elements of climate
2. Discuss three ways by which vegetation affects soil formation.

See also

ROCK WEATHERING

ROCK FORMATION AND TYPES

AGRICULTURAL ECOLOGY

HUSBANDRY AND CULTIVATION OF SOME SELECTED CROPS

POST–PLANTING OPERATIONS