Industrial wastes and agricultural pollutants such as pesticides, fertilizers etc are major sources of soil pollution.
The quality and fertility of soils should be maintained to ensure and sustain the growth of plants and food crops.
DDT is water insoluble. Hence, DDT (and other such insecticides) remain in soil for a long time and contaminate the root crops.
Pesticides such as Aldrin and Dieldrin are non biodegradable and highly toxic in nature. They can enter the higher trophic levels through food chains, causing metabolic and physiological disorders. The same is true for industrial wastes that comprises of several toxic metals such as Pb, As, Hg, Cd etc.
Control measures :
The addition of pollutants to the soil should be avoided. Also, proper treatment should be given to wastes. They should first be recycled and then dumped.