Soil degradation means decline in quality and quantity of soil.
Soil requires certain nutrients including organic matter to sustain plant growth. But with the advancement of agricultural practices, excessive use of pesticides, herbicides and fertilizers, in sanitary habits, improper disposal of solid wastes as well as fall out of dust particles from industries and thermal plants, etc., soil pollution has increased considerably in recent days.
Since ‘an empty soil cannot support or give rise to a high civilization and culture,29 it is an imperative need to conduct studies relating to soil ecology and concerned problems.”
The main factors of soil pollution are accelerated rate of soil erosion consequent upon major land use changes (e.g. deforestation), excessive use of chemical fertilizers, pesticides, insecticides and herbicides, polluted waste water from industrial and urban areas, a few micro-organisms, forest fires, dumping of urban and industrial solid wastes, water logging and related capillary process, leaching processes, drought etc.
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Agricultural expansion and development cause environmental degradation and pollution through land use changes (i.e., deforestation and cultivation) and introduction of modern technologies. The soils are extensively polluted through large-scale chemicalization in the developed countries while the land is being degraded due to ever increasing population in the developing countries.
The increased rate of soil erosion caused by deforestation for increasing agricultural land to increase the food supply in view of increasing population causes chain effects on environmental conditions in the affected areas as well as in the far off regions, e.g., deforestation causes soil erosion which causes loss of fertile top-soils and thus decreases productivity, soil erosion increases sediment load of the rivers which causes siltation and the rise of the river beds which results in the reduction of water accommodating capacity of the river valleys which thus increases the frequency, magnitude and dimension of floods which damage agricultural crops in the flood plain areas.
Anthropogenic factor has recently become most important factor of accelerated rate of soil erosion resulting in the depletion of soil nutrients and thus soil fertility.
The human activities responsible for soil erosion fall in three broad categories, e.g.: (i) land use changes (removal of forest and grassland covers for increase in agricultural area, space for industrial expansion and urbanization, for expansion of mining, for construction of rails, roads, reservoirs, dams etc.) (ii) Farm practice changes (greater use of machines for ploughing and harvesting, frequent changes in the nature of farming and cropping patterns etc.) and (iii) management measures (crop and land-management).