Effect of Paraquat on Soil Microorganisms

Pesticides are widely used in agriculture for pest control but inadvertently affect soil microbial communities. This study determined the effect of Paraquat on soil microorganisms. A microcosm study was conducted to investigate the effect of thepesticide on soil microorganisms, over a 7-day period. Five different treatments were set up: T1 (control); T2, 10kg of soil + 50 ml of pesticide, T3; 10kg of soil + 100ml of pesticide, T4; 10kg of soil + 150 ml of pesticide, T5; 10kg of soil + 200 ml of pesticide. Microbial population was determined by standard plate count. Bacterial and fungal isolates were characterised based on their cultural characteristics and biochemical tests. The results showed that the bacterial and fungal population in treated soil, decreased significantly (p<0.05) at higher concentrations of pesticide (T4 and T5). The bacteria Pseudomonas sp., Micrococcus sp., Bacillus sp., Staphylococcus sp. and Arthrobacter sp., and the fungi Penicillium sp., Aspergillus sp., Trichoderma sp., and Fusarium sp., were identified as the pesticide degrader/utilizers. This study suggests that the exposure to pesticides negatively impacts the survival and proliferation of soil bacteria and fungi. The use of pesticides should be avoided or in unavoidable cases reduced to the minimum to protect soil microorganisms.