Soil Degradation and Soil Conservation – APSC Exam Notes
Geography Notes APSC, UPSC and State Exam Notes
Soil degradation as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse. It is the main factor leading to the depleting soil resource base in India. The degree of soil degradation varies from place to place according to the topography, wind velocity and amount of the rainfall.
Causes of soil degradation
- Soil erosion
- Water logging
- Decline of soil fertility
- Salinity
- Shifting cultivation
Soil erosion
Removal/destruction of the top layer of soil by various means, which include both natural events and human activities, is called as soil erosion. The soil forming processes and the erosional processes of running water and wind go on simultaneously. The rate of removal of fine particles from the surface is the same as the rate of addition of particles to the soil layer. When this balance is disturbed by natural or human factors, leading to a greater rate of removal of soil. Soil erosion is a serious problem for Indian agriculture.
Human factors
- As the human population increases, the demand on the land also increases. Forest and other natural vegetation is removed for human settlement, for cultivation, for grazing animals and for various other needs.
- Deforestation is one of the major causes of soil erosion.Forests have been denuded especially in hilly parts of the country.
- A large area of arable land in the irrigated zones of India is becoming saline because of over-irrigation. The salt lodged in the lower profiles of the soil comes up to the surface and destroys its fertility.
Natural factors
- Wind and water are powerful agents of soil erosion because of their ability to remove soil and transport it. It is significant in arid and semi-arid regions.
- In regions with heavy rainfall and steep slopes, erosion by running water is more significant. Water erosion which is more serious and occurs extensively in different parts of India, takes place mainly in the form of sheet and gully erosion.
- Sheet erosion takes place on level lands after a heavy shower. It is harmful since it removes the finer and more fertile top soil/humus.
- Gully erosion is common on steep slopes. Gullies deepen with rainfall, cut the agricultural lands into small fragments and make them unfit for cultivation. A region with a large number of deep gullies/ravines is called a badland topography. Ravines are widespread, in the Chambal basin.
- Eroded materials are carried down to rivers and they lower down their carrying capacity, and cause frequent floods and damage to agricultural lands.
# The largest area affected by soil erosion in India are Rajasthan and Madhya Pradesh.
Main agents of soil erosion
- Water
- Wind
- Waves and
- Glaciers
Consequences of soil erosion
- Loss of Fertility of top soil
- Decline in nutrients content as they are washed away by erosion.
- Reduction of underground water level.
- Loss of vegetation and habitat.
- Frequency of Drought and flood increases
Decline of soil fertility
- Soil fertility is mostly affected in the states of Punjab, Haryana, and U.P.
- Chemical fertilisers in the absence of organic manures are also harmful to the soil.
- Unless the soil gets enough humus, chemicals harden it and reduce its fertility in the long run. This problem is common in all the command areas of the river valley projects, which were the first beneficiaries of the Green Revolution.
The major reasons for decline of soil fertility are:
- Frequent cropping
- Unscientific rotation of crops
- Extensive and excessive use of chemical fertilizers
- Too much use of chemical pesticides
Water logging
If there is no proper drainage system in the land, the land will become waterlogged. The normal circulation of air will not be possible due to water logging and the amount of oxygen in the soil will decline.
Salinity
Soil will become saline or alkaline in low rainfall areas. When the sea water enters the land, the soil becomes saline. The presence of calcium carbonate beneath (kankar) the soil will act as impermeable to water and water gets logged as happened in Indira Gandhi canal regions of Rajasthan.
Shifting / Jhum cultivation
- This slash and burn method of cultivation is practiced mainly in North-Eastern India.
- After reaping the crops, the land is slashed and burned. The next cultivation will be in another plot and the burned land will let uncultivated for a period.
Earlier, the gap between two cultivations in a land was 10-20 years. Now, due to population increase and availability of land is reduced, the gap decreased to merely 2-3 years. - This causes major deforestation, environmental pollution, loss of habitat for wild animals etc. The burning of forest results in soil erosion and gradual degradation of soil.
Soil Conservation
- Soil erosion is essentially aggravated by faulty practices. The first step in any rational solution is to check open cultivable lands on slopes from farming. Lands with a slope gradient of 15 – 25 per cent should not be used for cultivation.
- Over-grazing and shifting cultivation in many parts of India have affected the natural cover of land and given rise to extensive erosion.
- Contour bunding, Contour terracing, regulated forestry, controlled grazing, cover cropping, mixed farming and crop rotation are some of the remedial measures which are often adopted to reduce soil erosion.
- Efforts should be made to prevent gully erosion and control their formation
- In arid and semi-arid areas, efforts should be made to protect cultivable lands from encroachment by sand dunes through developing shelter belts of trees and agro-forestry.
- Lands not suitable for cultivation should be converted into pastures for grazing.
- Lands should be classified according to their capability; land use maps should be prepared and lands should be put to right uses.
- Afforestation.
- Strip cultivation (cultivation in strips).
- Flood control by government initiatives.
- Reclamation of bad lands.
- Wind breaks in land; like trees at borders.
- Organic farming.
- Control/restrict shifting cultivation.
- Construction of proper drainage.
- Control of chemical fertilizers and pesticides in the market.