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Agrochemicals refer to inorganic fertilizers and pesticides. In the wake of green revolution, used of inorganic fertilizers and pesticides has increases enoromously for enhancing crop production.
An agrochemical is defined as a chemical such as a fertilizer, hormone, fungicide, insecticide or soil treatment that improves the production of crop.
An agrochemical is a substance used to manage an agricultural ecosystem. There is a community of organism (microorganisms, plants, animals) in a farming area.
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Agrochemicals include:
(i) Fertilizers,
(ii) Timing and acidifying agents,
(iii) Soil conditioners,
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(iv) Pesticides,
(v) Chemicals used in animal husbandry, such as antibiotics and hormones.
The use of agrochemicals raises crop production to meet to demand for food with increasing population. However, some of these chemicals cause substantial environmental and ecological damage, greatly reducing their benefits.
(i) Fertilizers:
These are added to formlands to encourage plant growth and to increase crop yields. Fertilizers may be chemically manufactured (synthetic) or be made from organic materials (living) such as recycled wastes, animal, manure or compost (decaying vegetation). Most chemical fertilizers contain varying amount of nitrogen, phosphorus and potassium which are inorganic (nonliving) nutrients that plants need to grow. About 138 million metric tons of fertilizers are used globally each year.
(ii) Liming and acidifying agents:
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Crops planted in soil that is either too acidic or too alkaline cannot obtain the proper nutrients they need to grow from that soil. Acidic soils can be caused due to acid rain (precipitation that contains weak sulphuric acid and nitric acid) and use of certain fertilizers. Acidic soil is a serious problem in agriculture i.e. in yield of crops. Acidic soils are neutralized by adding compounds that contain calcium usually in the form of powdered limestone or crushed oyster or mussel shells.
(iii) Soil conditioners:
These are materials added to soil to increase its ability to hold water and oxygen. Materials used as soil conditioners include peat, livestock manure sewage sludge and even shredded newspapers. Compost is probably the best soil conditioner because it keeps soil from becoming too acidic or too alkaline and it supplies organic nutrients to the soil.
(iv) Pesticides:
Pesticides are used to eliminate the presence of pests, any living organisms that cause injury or disease to crops. According to the targeted pests, the pesticides used in agriculture can be categorized into a few groups.
(a) Herbicides are used to keel weeds, any non desired plant that interferes with the growth of crops.
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(b) Fungicides are used to protect agricultural plants from fungal diseases.
(c) Insecticides are used to kill insects that eat crops or stored grains.
(d) Other pesticides target snails, slugs, miles, rodents and birds.
Very large quantities of pesticides are used in modern agriculture. About 2 to 3 billion kilograms of pesticides are used each year globally, at a total cost of about 20 billion U.S. dollars.
(v) Agrochemicals used for animal husbandry:
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Livestock animals are given agrochemicals in the form of antibiotics either by injection or combined with feed to control infectious diseases and parasites. Various hormones are administered regularly to increase the growth and productivity of animals.
Environmental effects:
On one hand, agrochemicals increase plant and animal crop production and on the other hand they cause of a lot of damage to the environment. Excess use of chemical fertilizers has led to the contamination of ground-water with nitrate which is poisonous to man and animals in large concentrations. The runoff fertilizers into ponds, streams, lakes and other surface waters can increase algal growth leading to death of fishes and other aquatic animals.
Insecticides like DDT remain active in the environment for many years, contaminating all wild life, food grains and surface water including humans. It is now known that millions of wild birds are killed every year in North America due to exposure from agricultural insecticide carbofuran.
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Control Measures:
Various environmental effects due to agrochemicals have created worldwide concern. Now, the approach is to shift from chemical methods to non-chemical methods of enhancing soil fertility and dealing pests. The alternatives are very expensive and not yet in widespread use. The United Nations Environment Program organised a meeting in the year 2000 and banned the production and use of twelve persistent organic pollutants, especially those used as pesticides. These twelve chemicals have been named as “dirty dozen”.
Eight of them are pesticides such as aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex and toxaphene. To control malaria in Africa, DDT has been given special exemption. One hundred and twenty two nations including USA have accepted the treaty but time will prove how many of them will really implement it.
