The fertility of the soils varies not only from place to place, but also from one type to another. It depends upon its origin, the elements present in it, its texture and structure. The organic and inorganic materials provide the necessary requirements for plant food.
The fertility can be disturbed by natural forces, such as running water, wind and ice, and human activities, such as cultivation, deforestation, overgrazing, etc.
Generally, the rate of removal of soil particles by the denudational processes is equal to the rate at which soil particles are added to the layer by soil forming processes. When this equilibrium is disturbed, i.e. the soil particles are removed from the surface at a faster rate by the agents of gradation. This condition indicates soil erosion, and this process continues. The entire soil layer can be removed in a few years.
Image Source: tunza.eco-generation.org
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The rate of soil erosion depends upon the nature of the soil, the slope of the ground, the density of vegetation cover and the character of the rainfall. Soil erosion is mainly of three types.
1. Sheet erosion
2. Gully erosion
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3. Wind erosion
The soil erosion is going on regularly in different parts of our country. This evil has assumed alarming proportions and the total area affected is more than 5, 00,000 square kilometres. It is adversely affecting our agricultural productivity and the economy of the country.
Apart from lowering land productivity, soil erosion results in frequent river floods, lowers the water table and increases aridity. It makes land unfit for agriculture. The land so developed after soil erosion, is called badland. In our country, soil erosion is increasing, at an alarming rate.