How does planting of trees help to conserve soil? Why should chemical fertilizers be used with caution?
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Excessive use of fertilizers and pesticides by farmers in agriculture to enhance crop yield is detrimental to environment and human health. Fertilizers and pesticides use has led to the problem of air, water and soil pollution. The nitrous oxide (N2O) produced by microbial action on inorganic fertilizers in soil causes depletion of stratospheric ozone layer, which serve as shield against harmful UV-rays emanating from the sun.
Fertilizers applied to the field are drained by rain water to rivers and lakes causing water pollution. The phenomenon of nutrient enrichment of aquatic bodies is known as eutrophication, which deteriorate the water quality leading to death of fishes. Moreover, the seepage of fertilizers and pesticides also pollutes the ground water.
Pesticides such as DDT are non-biodegradable and are fat-soluble which enter the food chain and reach the human body where they are deposited in adipose tissue. When oxidation of the fat takes place, the pesticides are released in the system causing harmful effect to human health.
Endosulphan is a commonly used pesticide for the control of pests in rice crop is highly hazardous as it causes serious eye, kidney and liver disorders. The harmful effects of endosulphan on human health have been reported from the state of Kerala in Indi. The concentration of pesticides increases with increasing food chain and the phenomenon is known as biomagnification or biological amplification. India's daily diet is reported to contain 270 µg of DDT. The concentration of DDT in Indians has reached to alarming proportions ranging between 13 to 31 ppm (parts per million). There have been reports of cases of cancer, deformities, hepatic diseases and neurological disorders due to pesticide poisoning in cotton growing belts of India.
The excessive use of nitrogenous fertilizers decreases the potassium content of the food grains. Potassium is important element, which controls the rise in blood pressure and also avoid the risks of heart attack. The excessive potash treatment decreases valuable nutrients in foods, such as ascorbic acid (vitamin C) and carotene. Vitamin C boosts the defense system while carotene is the precursor of vitamin A, which is important for the vision. The nitrate fertilizer increase the crop yield (carbohydrate) but at the cost of proteins. Moreover, subtle balance of amino acids is disturbed within the protein molecule thus lowering the protein quality. Therefore, the escalating problem of cardiovascular disorders, hypertension, night blindness and other eye disorders, malnutrition and susceptibility to infectious diseases is owing to excessive use of chemical fertilizers in agriculture.