FOR better agricultural production and elimination of wild flora and fauna from fields, extensive application of fertilisers and pesticides play a significant role. But excessive use of these inputs have a number of undesirable effect on environment. They also adversely affect the biodiversity at various levels among plants and animals both vertebrates and invertebrates.

In pre-industrial agriculture animals were valued not only as producers of milk and meat, but also as source of manure essential for fertility of soil. Mechanisation of agriculture and introduction of chemical fertilisers and industrial foodstuff from the middle of 20th century have separated the age-old link between crops and livestock farming.

With technological advancement in quest for better harvest and secure food production, traditional methods have been abandoned. During the last few decades agriculture all over the world has transformed into "industrial agriculture." Use of fertilisers in agriculture is both desirable and detestable as far as crops health and their effect on environment and associated biodiversity is concerned.

In the 1920s machines began to replace human and animal power for preparing soil, planting, weeding, and harvesting. Since the 1930s, high-yielding crop varieties started replacing traditional varieties. Most of these new varieties require application of synthetic inputs such as pesticides and fertilisers, which have brought agricultural revolution. In the last half of the 20th century grain production increased tremendously at the cost of ecological upsets and disruption of the natural equilibrium.

Due to industrialisation, mechanisation and evolution of new concepts, large-scale changes in practices have been observed which has resulted in decline of crop diversity. Traditional farms grow grains, root crops, vegetables, spices, medicinal plants, livestock, and trees for timber, fruit, and firewood. In contrast, most modem farms are monocultures — that is, they have only one crop species planted over a large area thereby having less associated diversity such as insects, birds, and soil organisms and are more beneficial to plants. With the use of chemicals, pesticides and insecticides, the relation of plants and soil organisms has largely been changed.

The practice of monoculture rely more on use of pesticides. In order to get rid of pests and other pathogens (disease-causing organisms) pesticides or insecticides are applied. These pests can readily find their food sources easily in homogenous crops or monocultures than in heterogeneous crops or diverse crop mixtures. Therefore, in monocultures there is lower population of biological control agents such as spiders, wasps, dragonflies, and predatory beetles, which are enemies of pests.

It has often been experienced that to control pest and secondary outbreaks of pest, application of pesticides or more toxic chemicals are needed to minimise its effects. This induced fertility of farm lands with modern agricultural techniques cause tremendous erosion and contamination of soil top.

Owing to increased demand for use of industrial inputs in agriculture, the genetic diversity of crop has also been affected. Earlier hundreds of plants producing edibles were grown in different parts of the world, but now about 60 per cent of the world diet constitutes of rice, wheat and corn. This can be attributed to replacement of high yielding plant and crop varieties, causing genetic erosion.

Genetic erosion is a nightmare in agriculture sector due to which important species and varieties would be eliminated causing an irreparable loss. According to the Food and Agriculture Organisation (FAO), 75 per cent of crop diversity was lost during the 20th century. Modern varieties have supplanted traditional varieties for instance 70 per cent of word's corn, 75 per cent of Asian rice, and half of wheat in Africa, Latin America, and Asia. In 1950, India had 30,000 varieties of rice, but by 2015 only 50 are expected to remain.

Uses of fertilisers and pesticides have dire impact on biodiversity at the micro level resulting in dire consequences in the long run. Many birds of some species have died after eating sprayed insects. Pesticides from agriculture fields flow into aquatic systems through surface water, soil erosion, and drainage into groundwater. Pesticide residues in streams, lakes, bays, and coral reefs kill aquatic plants and zooplankton (microscopic animals) which fish require for food. Pesticides in water increase mortality of young fish and amphibians as fertilisers and pesticides release harmful chemicals into lakes, and rivers causing pollution. Spray of toxic chemicals on crops for controlling pests threatens many important species -pollinators and soil organisms.

In the past farmers applied minimum chemical fertilisers for better yield, but today they apply eight times more fertilisers to grow more crops to meet the increased demand. In global perspective, according to an estimate, use of fertilisers in northern Europe has increased from about 45 kg/ha to 250kg/ha since 1950. In the same period, wheat yields in France increased every year, from about 1.8 tonnes/ha to more than seven tonnes/ha. Fertiliser application currently accounts for 43 per cent of the nutrients that global crop production extracts each year, and the contribution may be as high as 84 per cent in the years to come.

There is a consensus about the way agriculture is evolving in response to demographic and economic trends. World population will probably grow to some 8,000 million around 2030, when two out of every three people will live in towns and cities. Rising incomes will create a disproportionately higher demand for food, meaning that over the next three decades food production will need to increase by about 60 per cent. These increase in production will come from developing countries through intensified agriculture production, i.e. more yield per unit time and per unit area.

Mismanagement of fertilisers results in inefficiencies of plants’ nutrient use, leading to loss in farmers’ profits and potential damage to environment. One of the most serious problems associated with the improper use of fertiliser is a sustained imbalance in the application of nutrients, causing a loss in soil fertility, reduction in crop yield, and degradation of environment. When nutrients are over-applied, they can have an adverse effect on water quality, both surface and groundwater. This also reduces efficiency and fertility of the soil.

After having realised the harmful affects of excessive use of fertilisers, particularly in the mountainous fragile ecosystem, people have reverted to organic farming again. Composting is now considered to be one of the most effective measures, which is a natural way of recycling and harnessing natural processes rather than machinery and artificial chemicals. This has proved that to increase soil fertility not only benefits crops but also local biodiversity in the long run without any negative impact. In order to grow healthy plants and crop it’s important to feed the soil than to feed the plants.

In face of expanding human population and increasing food demands from the depleting agricultural lands due to urbanisation, there is need to focus on sound management and ecologically desirable practices to ensure better crop production and benefit the biodiversity without influencing fertility of the soil in a natural way.