A pesticide is a substance or a mixture of substances used for preventing, controlling, or lessening the damage caused by a pest (Parads, G. et al., 1995). A pesticide may be a chemical substance, biological agent (such as a virus or bacteria), antimicrobial, disinfectant or device used
against any pest. ( USEPA, 2007 ).
Pesticides are used to control organisms which are considered harmful. (Purdue.edu, 2007). Pesticides can save farmers money by preventing crop losses to insects and other pests; in the US, farmers get an estimated four>fold return on money they spend on pesticides (Kollogg RL,
et. al, 2000). One study found that not using pesticides reduced crop yeilds by about 10%.(Kuniuki S, 2001).
The first recorded use of pesticide to protect crops was 4,500 years ago (Miller, GT. 2002). In 1993 Paul Muler discovered that DDT was a very effective insecticide. In 1940s, manufacturers began to produce large amounts of synthetic pesticides and their use became widespread (Daily, H, et al., 1998). Pesticide use has increased 50>fold since 1950 and 2.5 million tons (2.3 million metric tons) of industrial pesticides are now used each
year (Miller, G. T. 2002).
In the 1960s, it was discovered that DDT was preventing many fish> eating birds from reproducing, which was a serious threat to biodiversity.
Rachel Carson wrote the best> selling book Silent Spring about biological magnification. DDT is now banned in at least 86 countries, but it is still used in some developing nations to prevent malaria and other tropical diseases by killing disease> carrying insects (Lobe, J. 2006).
Many of the chemicals used in pesticides are persistent soil contaminants, whose impact may endure for decades and adversely affect soil conservation (USEPA, 2007).
The use of pesticides decreases the general biodiversity in the soil.
Not using the chemicals results in higher soil quality(Johnston , A.E. 1986), with the additional effect that more organic matter in the soil allows for higher water retention (Kollogg, R.L., 2000). This helps increase yields for farms in drought years, when organic farms have had yields 20>40% higher than their conventional counterparts (Lotter, D. et al., 2003)a smaller content of organic matter in the soil increases the amount of
pesticide that will leave the area of application, because organic matter binds to and helps break down pesticides ( Kollogg, R. L., 2000).
The capacity of the soil to filter, buffer, degrade, immobilize, and detoxify pesticides is a function or quality of the soil (Cameron, et. al., 1996).
Soil quality also encompasses the impacts that soil used and management can have on water and air quality, and on human and animal health (Stolze et. al., 2000). The presence and bio>availability of pesticides in soil can adversely impact human and animal health, and benifical plants and soil organisms. Pesticides move off>site contaminating surface and ground water and possibility causing adverse impacts on aquatic ecosystems (Jaenicke, E.C., 1998).
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