Some of the aspects of land degradation are discussed below:
1. Loss of Fertility by Mismanagement:
Man, in his urge to derive the maximum yield to satisfy vast needs of a rapidly growing population, has been resorting to various scientific inputs like irrigation, fertilisers, pesticides etc. At the same time, unscientific cropping practices are sometimes followed.
For instance, at some stretches of Western Ghats, commercial tuber crops like potatoes and ginger are grown on slopes, after clearing the forests. These unscientific farming practices and an excessive use of inputs result in problems like soil erosion, loss of natural nutrients, water-logging and salinity and contamination of ground and surface water.
2. Soil Erosion:
This is the process by which the top soil is detached from land and either washed away by water, ice or sea waves or blown away by wind. An area of around 8C mHa is exposed to the threat of soil erosion, while 43 mHa is actually affected.
This problem occurs in areas of temporary water surplus and high temperatures. Due to over-irrigation or high rainfall, the moisture percolates down and dissolves the underground salts in it. During the dry period, this solution comes to the surface by capillary action. The water gets evaporated, leaving behind a crust of salts of sodium, magnesium and calcium which has a fluorescent appearance.
This salt layer plays havoc with the fertility of top soil and renders vast stretches of useful land infertile. This problem is particularly serious in areas with assured irrigation in Punjab, Haryana, Uttar Pradesh, western Maharashtra, Bihar and northern Rajasthan (the Indira Gandhi Canal command area). Such lands are known by local names, such as reh, kallar, usar, chopan etc. An area of around 6 mHa suffers from the problem of salinity/alkalinity.
This happens when the water table gets saturated for various reasons—over- irrigation, seepage from canals, inadequate drainage or presence of a hard pan below. The land under waterlogged conditions can be used neither for agriculture nor for human settlements. In dry areas, waterlogging leads to salinity and alkalinity. This menace can be tackled by adopting scientific norms for amount of irrigation, checking seepage from canals by proper lining and providing adequate drainage through field channels.
5. Floods and Droughts:
Both these hazards have the harmful effect of limiting the use of good soil. One nagging aspect of floods is that each year a new area is affected.
Advancement of sand from the desert to the adjoining regions is called desertification. The sand covers fertile soil and affects its fertility. This problem is particularly serious in areas adjoining the Thar desert in Rajasthan. The affected areas lie in the states of Punjab, Haryana, Delhi, Madhya Pradesh and the Aravalis in Rajasthan.
Measures to Check Land Degradation:
Around 145 million hectares area of the country is in need of conservation. The decline of natural fertility can be checked by applying controlled amounts of chemical fertilisers. In general, improved agricultural practices in different regions need to be adopted. Tillage on higher slopes should be avoided, while contour ploughing on the slopes prone to erosion may help in maintaining the soil depth.
Planting of shelter belts and stubble mulching help in conserving the soils in desert regions. The ravines and gulleys should be plugged to prevent head-ward erosion. The pressure of livestock on pastures in hilly, desert and plateau regions has to be reduced in order to avoid overgrazing, such as in Jammu and Kashmir, Himachal Pradesh, Rajasthan and Karnataka.