Soil Pollution

Soil sustains innumerable microbes and a large number of plants and animals along with plenty of mineral reserves for purposeful exploitation. Soil has different meanings for different people. Chemists consider the soil an object endowed significantly with high buffering capacity while to a geologist, the soil is a means for ascertaining the age of the earth from a large number of isotopes present in it. The soil to a limnologist is a dependable source of nutrition for the biota, and to a farmer, the soil in the form of land is a source of living whereas to a sanitary engineer, it is nothing more than dumping ground for all kind of wastes. Above all, the soil is a living record from where originated all major ecological events of the past.

    India is loosing nearly 6000 million tons of topsoil per year in Ganga Basin alone, caused mainly by ruthless deforestation, thus leading to severe erosion problem.

Sources of Soil Pollution

There are numerous sources. Important among them are listed here:

1. 
   
   Indiscriminate discharge of industrial effluents on land and in watercourse.
   
2. 
   
   Open defecation by animals and human beings especially in the rural parts.
   
3. 
   
   Unscientific disposal of solid waste on land
   

In developing countries like India, the major source of soil pollution is of the third type, and is prevalent in both rural and urban as well as in rural regions. The garbage generated by the community in India contains 30-40 percent of composable matter from which good qualities of manure can be obtained from anaerobic process. Indian refuse, usually contain less than 1 percent of plastic and glass material. The paper content of the refuse varies between 3-7 percent. Generally, the people with modern scientific vision produce less refuse than those with poor and dirty living habits. Based on the comprehensive survey conducted by it on the overall physico-chemical composition of the refuse NEERI has recommended scientific conversion of the refuse into compost. Accordingly, a composting plant with a capacity of 200 tons per day of manure production has been installed at Calcutta. All other big and medium size Indian cities must follow similar practice to keep their environment clean. Radioactive substances produced during fission and fusion enters in to the life supporting environmental cycles.

More widespread than desertification, if less dramatic, is the gradual deterioration of agricultural soils, particularly in, dry land areas. Results of a global assessment of soil degradation sponsored by U.N.E.P. show that 1.2 billion -hectares-almost 11% of the earth's vegetation, surface have undergone moderate or worse soil degradation over the past forty five years because, of human activity. As a result of this deterioration yields and total harvests of important crops are declining in a number of countries. Erosion is one of the key components of soil degradation.

Its irreversibility and its potential effects distinguish it from the other critical elements of soil deterioration. Loss of plant nutrient, organic matter, and microorganisms. Soil erosion is actually removal or erosion of top layer of the soil hence involving loss of fertile layers of the soil. Its main causes are high velocity and heavy rains.

As rainwater drains over the surface of the ground, it picks up, and transports particles of soil more or less proportional to the rate of flow. This is a continuous process that has gone on throughout geological time, resulting in base level in mountains, and the formation of river-deltas. Normally this is a slow process, the changes becoming apparent only in thousand years. With the ground covered with vegetation, the flow of water is retarded arid more of it percolates into the ground or is evaporated. In fertile areas, new soil is formed faster than it is eroded or at least there is stabilization.

With removal of the native vegetation and cultivation of the soil in agriculture, surface particles are more easily moved and surface water drainage is more rapid. As a result, topsoil is being lost at an alarming rate. Much land has been so badly damaged that there is little likelihood that it will ever again be productive crops. Conservation of the fertile topsoil is one of major problems facing modern agriculture. Putting in underground drainage tiles in level farmlands helps to draw rainwater into the soil and to decrease surface run off and erosion. Soil conservation procedures should be strictly followed.

Agronomic research and project experience are revealing that erosion is best prevented through balanced management of soil moisture, nutrition and organic matter. Low cost techniques for soil conservation, designed to improve soil moisture levels, can increase yield sufficiently within the first several years to make the inventions profitable in their own right, regardless of the long run benefits of soil conservation. Compared with traditional cropping methods, practices such as mulching, manuring, low tillage, contour cultivation and agro forestry can reduce surface runoff, water sediment loss and erosion by 50 percent and more. They will contribute to the control of soil degradation only if practical constrains such as shortage of cash and labour and the use of dung and mulching material as household fuels are first alleviated.

With the rapid expansion of irrigation over the past forty years have come growing problems with salinisation and waterlogging that are eating away at the productivity of irrigation investments. Irrigated land is deteriorating in parts of many countries including China, Egypt, India, Pakistan, the Central Asian Republics and Western United states.