Chemical Control

Nowadays, different chemicals are used in agriculture for different purposes. Which include pesticides to kill pests and prevent the crops. Herbicides are also common for kill weeds, fungicides for killing fungi and insecticides for killing insects. By using theses pesticides, more crops can be grown to feed the increasing population. However, there are undesirable effects to the environment by the use of pesticides.

The wide variety of pesticides can upset the ecosystem. As most pests have natural enemies that prey on them, pesticides decrease the efficiency of the predator in controlling the prey population. Also, as the pests are the main food source of the predator, predators will not be able to survive if the pests are killed. If the pests start to flourish again the natural enemies are no longer present to keep them down. The wiping out of natural predators can also unleash new pests that have been held in controlling previously by those predators. Another problem is that frequent use of pesticides promotes the development of new strains of pests that are resistant to these chemicals. Insects breed rapidly and develop genetic resistance to insecticides through natural selection. Weeds may also develop genetic resistance to herbicides. So it will be more difficult to control the new strains of pests. Pesticides also affect food chains. Pesticides can be easily sprayed and disperse in the air and water reaching non-target area. They will be taken up and enter into the food chains. They may be toxic and may affect the organisms. Many of the pesticides that cannot be metabolized or excreted will accumulate in the body of organisms and will be passed along the trophic levels. Organisms in the higher trophic levels will accumulate and have a high concentration of pesticides. Pesticides will also be washed away by rain from the farmland to aquatic bodies. They may accumulate in phytoplankton and significantly reduce their amount. The oxygen released by photosynthesis of phytoplankton may not be enough to support any other aquatic life, and more carbon dioxide will accumulate causing global warming. Pesticides will also accumulate in soil and may kill the decomposers. This decreases the availability of minerals to plants. If nitrifying bacteria are killed, toxic nitrites will be accumulated in the environment.

Another kind of chemical commonly used in agriculture is fertilizer. Fertilizers provide minerals for the development of crops. They normally include nitrogen, phosphorus, potassium, calcium, magnesium and sulphur, which are required in varying quantities according to the crops being cultivated. They replenish nutrients to crops. Organic fertilizers such as manure and plant wastes or inorganic fertilizers such as commercial chemical fertilizers are either used to restore the plant nutrients. However the excessive use of inorganic fertilizers cause various environmental problems.

Chemical fertilizers will cause soil destruction. The use of chemical fertilizers replaces the organic fertilizers in the soil. So the soil will become lack of humus or organic matter, and the water retaining ability will be greatly reduced. The soil will become compact and less suitable for crop growth. Chemical fertilizers will also cause water pollution. The intensive use of chemical fertilizers may cause serious water pollution problems, especially for slope farmlands near streams and lakes. Fertilizers will be easily washed into the aquatic bodies by heavy rainfall. The water will be rich in nutrients and will cause rapid growth of algae forming algal bloom. This will lead to the depletion of oxygen and death of fish and other aquatic life. Also, the production of chemical fertilizers consumes a large amount of energy and harmful gases are released into the atmosphere, which lead to air pollution and global warming. Furthermore, rainwater seeping through the soil can leach the fertilizers into underground water, so they will be contaminated with toxic affecting our health.

As many chemicals used for agriculture is harmful to the environment, we should be vigilant when using them. We should not use excessive chemicals during agriculture and try to use organic ones to replace the harmful chemicals for pesticides and fertilizers. By doing so, we can keep the well being of the environment and can increase crop yield.