Abstract

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Pesticides are used to increase crop production. Besides combating pests, pesticides affect the activity of beneficial soil microbial communities thereby affecting the nutritional quality of soils. This study investigated the impact of pesticides on the ecological activity of microorganisms in LASUSTECH agricultural field. Twenty milliliters of Fungicides (Copper (1) oxide metalyxl and 2,3-Dichlorovinyl dimethyl phosphate (DDVP), Insecticides (Chlorpyrifos, Cyperrmethrin, Deltamethrin and Dimethoate) and Herbicide (Glyphosphate) was separately added to 2000g of soil. The microbial counts were examined by serial dilution and plating methods weekly for four weeks. The results demonstrated a decrease in the microbial count in all the soils treated with pesticides and the controls but the percentage decrease in soils with pesticides is higher than the percentage decrease in the controls. The highest decrease in bacterial count was recorded in soil treated with Deltamethrin (from 20 to 7 x 105cfu/mL) and the lowest decrease was recorded in the soils treated with Cypermethrin (from 40.5 to 20.5 x 105 cfu mL), DDVP (from 43 to 23 x 105 cfu mL). For fungi, the highest decrease in population was recorded in the soil treated with DDVP (from 23 to 6 x 106 cfu mL) and the lowest decrease was observed in the soil treated with Chlopyrifos (from 7 to 3.5 x 106 cfu mL).In conclusion, this study has shown that the investigated pesticides significantly decreased the microbial population in soil. This confirms and reinforces the reports that prolong use of pesticides in soil destabilizes soil microbial activity and ecology.

Keywords: Fungicides, Herbicides, Insecticides, Microbial- ecology, Pesticides.