Factors of Soil Formation

Factors of Soil Formation

Parent rock, relief, time, climate and plant and animal organisms are responsible for soil formation.

Parent rock, relief and time these three factors are called the passive factors.

Climate and plant and animal organisms are active factors.

The parent material and climate are the most important factors.


Parent rock

A soil is derived from the parent rock.

Parent rock material contains different minerals.

After broken down into tiny pieces, parent rock gets decomposed by physical and chemical weathering.

It furnishes inorganic mineral particles of the soil.

The parent rock influences the rate of soil formation, chemical composition, color, texture, structure, mineral content, and fertility.



Topography influences the degree of erosion of the material in the parent rock and the rate of surface runoff water.

Steep slopes are prone to a higher runoff of water than gentle slopes.

Because of this, there is less water infiltration on steeper slopes, which slows down soil formation processes.

Moreover, rapid run-off on steep slopes frequently erodes their surface faster than the soil can create.

This is why mountain topography produces coarse, thin and infertile soil and the plain areas have rich and well-developed fertile soils.



The soil-forming process is very slow.

Well-developed soil results as an end product of physical, chemical and biological processes that have been working together for a very long period of time.



Climate Not only does it tend to reduce the difference caused by the parent material, but it also affects the biological activity of the soil.

Because of this aspect, in one climate region type, two separate parent materials may grow the same type of soil.

For instance, in the dry Rajasthan desert granite and sandstone have formed into sandy soil.

On the other hand, two different types of soils in two climatic regions can grow from the same parent material.

For example, in monsoon regions, the crystalline granites formed laterite soils and in sub-humid regions, non-laterite soils.


Plant and Animal Organisms

Plants and animals play an important role in turning parent materials into mature soil.

The organic material of the soil is added by dead plants and animals.

The decay process, added by bacterial action, turns organic matter into humus.

Humus is responsible for soil fertility.

Humus also improves the soil’s capacity to hold water.

The plant cover, in turn, protects the rich upper layer of the soil from erosion by increasing the proportion of rainfall entering into the soil rather than running off the surface.

The thick canopy often prevents greater evaporation of soil moisture, allowing the soil to mature and become fertile.


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