The removal of the top fertile soil by any agency like wind or water is called soil erosion. It is very harmful as it can lead to landslides and other imbalances in nature. Moreover, it takes 900 years for a single inch of land to form, which can be easily washed off by a single shower of rain or a single blow of wind. So, it must be prevented and following are the measures to prevent soil erosion-
By planting trees and grass excessively and reducing deforestation. The purpose of planting trees is that the roots of trees can hold the soil firmly and do not allow it to run away.
By no allowing the field to lie fallow, i.e., ploughed but unsown for a long time.
By proper irrigation, drainage and binding in the fields so that the water which flows from the field should not carry the topsoil with it.
By intensive cropping and terracing of sloping lands, i.e., growing plants in layers around the hill so that water cannot drain away down the slope and take the fertile topsoil with it.
Preserving Soil Fertility:
The soil which is deficient in the mineral elements required for proper growth and development of plants is the infertile soil. This soil fails to give high yield in terms of food. The soil fertility can be preserved by following ways-
By preventing soil erosion. Due to soil erosion, the top valuable and fertile soil is washed away, thus reducing the fertility of the soil. If different methods to prevent soil erosion are used, the fertility of soil can be preserved.
By not keeping the fields uncultivated for a long time. In this way, the soil is not exposed to wind erosion and loss of fertility.
By rotation of crops– A particular type of crop grown again and again in the same field makes the soil devoid of nutrients which that crop requires. Now, leguminous plants such as pulses, peas and beans contain nitrogen-fixing bacteria in their root nodules. These bacteria fix up atmospheric nitrogen and make the soil fertile. If the main crops and the leguminous plants are rotated (example- pulse crop grown between two cereal crops), then all nutrients in the soil remain in balance and, thus the soil fertility is preserved.
By using fertilizers– Soil is said to be a complex mixture of physical, chemical and biological materials. These materials must remain in the soil in suitable quantities. For this purpose, it is essential to use fertilizers which can replenish the soil.
By using cow-dung and dead leaves. Cow-dung and dead leaves are the ideal manure for making the soil rich in nutrients. It these are mixed in the soil, these can replenish the soil.