Page 95 - Scientech 2016-17

deficiency in crop plants. Nitrate fertilizer increase the crop yield (carbohydrate) but at the
expense of proteins. Excessive fertilizer use produces over-sized fruits and vegetables, which
are prone to insects and other pests.

The fertilizers used to raise the crop yield are drained by rain water to the adjacent fresh
water bodies like rivers, lakes and ponds causing nutrient enrichment (especially nitrate
and phosphate) of the aquatic bodies. This phenomenon is called as ‘eutrophication’, which
triggers the luxuriant growth of blue green algae (cyanobacteria). The algal growth forms
floating scums or blankets of algae called as algal blooms. Blooms of algae are generally not
utilized by zooplanktons.

The pesticides moving from crop fields to aquatic
bodies affect the aquatic flora and fauna. Many
of non-biodegradable pesticides (Chlorinated
hydrocarbons) like D.D.T., B.H.C. etc. enter the
food chain and reach the human body causing
harmful effect to human health. Generally the
concentration of the pesticides increases with
increasing food chain and the phenomenon is
known as biological magnification. India's daily
diet is reported to contain 270 µg of D.D.T. and the
level of accumulated D.D.T. in the body tissue of
an average Indian is highest in the world varying
between 13 to 31.0 ppm (parts per million). Cases
of cancer, deformities, hepatic diseases and neurological disorders from pesticide poisoning
have been reported from cotton growing areas of Gujarat, Maharastra and Andhra Pradesh.
Pesticide endosulphan used in aerial spray by Plantation Corporation of Kerala over the
areas of Kasargod and Rajapuram cashew plantation lead to severe cases of child blindness,
physical retardation and cancer in these areas.

The excessive use of nitrogenous fertilizers causes acidification of soil, resulting in the loss
of soil fertility. The indiscriminate use of pesticides to control pests kills several useful flora
and fauna of the soil, which promote soil fertility. Besides the targeted insects, useful insects
promoting cross and self-pollination are also killed. This leads to decline in crop productivity
owing to reduced rate of pollination accomplished by insects.

In conventional farming practices there is constant use of some high yielding varieties of the
crops in place of nutritive indigenous varieties resulting into uniformity in biodiversity. This
poses threat to the loss of biodiversity. The gradual loss of variability in the cultivated forms
and in their wild relatives is referred to as ‘genetic erosion’. This variability arose in nature
over an extremely long period of time, and if lost would not be reproduced during a short
time period. In conventional farming the loss of biological diversity is enhanced due to over-
exploitation of natural resources, excessive use of pesticides and environmental pollution.
Hence, the ecology in conventional farming is fragile.

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