In modern agriculture, high yielding varieties (HYV) are grown which require large amount of water supply, chemical fertilizers and pesticides. Hence it leads to following environmental problems:
a) Soil Erosion
Excessive water-supply and wind removes the top fertile layer of the farm. Loss of nutrient rich soil not only reduces productivity, but also results in silting of water bodies and streams and induces release of soil carbon from particulate organic material, which contributes to global warming.
b) Ground water contamination
Leaching of nitrates (NPK fertilizers) may cause ground-water pollution. E.g. haemoglobin combines with nitrite to from methaemoglobin which is unable to carry the oxygen so reduces oxygen uptake in the lungs.
What is methemoglobin?
A hematogenous pigment formed from hemoglobin by oxidation of the iron atom from the ferrous to the ferric state.
A small amount is found in the blood normally, but injury or toxic agents convert a larger proportion of hemoglobin into methemoglobin,which does not function as an oxygen carrier.
The disease caused is methaemoglobinemia (When more than normal level of methemoglobin is present in blood). Methaemoglobinemia further leads to cyanosis or blue baby syndrome. (the word cyanosis literally means the blue colouration)
c) Water-logging and salinity
Due to improper drainage, water gets accumulated in the farm known as water-logging. When water evaporates, it causes salinity in the soil. As a result the crop plants die.
When the water runoff with chemical fertilizers reach to the nearby water body small water plants grow in excess known as Algal Bloom. It prevents or stops intermixing of atmospheric oxygen to dissolved oxygen in water. The water plants and animals start dying due to lack of oxygen. The dead parts will deposit at the bottom of the water body. The process continues and cause threat to the water-body. The process is known as Eutrophication. The water body is known as eutrophic water body e.g. Chilka Lake in Orissa.
Concentration of the toxic substance increases several times when it is transferred from one organism to another, in the food-chain known as Biomagnification. E.g. increase in DDT concentration caused reproductive failure in birds i.e. their eggs hatch before time.
f) Seed Suicide
High yielding varieties (HYV) are used in modern agriculture, to produce more crop yield. They require large amount of water and fertilizers i.e. HYV are irrigation and chemical fertilizer intensive.
Hence excessive use of chemical fertilizers and pesticides kills the useful pests too.
However growing the same kind of seeds again and again also increases the chances of pest-attack. Thus the crop becomes vulnerable to pest attack. E.g. potato famine occurred in Ireland in 1969 due to pest attack on the complete crop due to monoculture.
Seeds of HYV do not germinate i.e. lose their viability every season due to terminator technology being used in their genes. Thus, farmers used to buy these seeds every year.
Seeds of High yielding varieties are very costly. Farmers are compelled to use these high yielding varieties seeds to increase their crop production and to gain profit.