Effect of pesticides on soil microorganisms

Abstract In light of the rapidly growing human population, extensive pesticides have been utilized to maximize crop production. This has become a major environmental concern. To assess the influence of commonly used pesticides on soil microorganisms counts and microbial activities in the form of CO2 production, a factorial experiment was conducted. Herbicide (Glyset I.P.A, Glyphosate 48%) and insecticides Miraj (Alphacypermethrin 10%) and Malathion (50% WP) were separately added to the soil at 0, 50, 100 and 200 ppm and incubated in the laboratory at 30 °C. The counts of bacteria, fungi, actinomycetes and CO2 production were examined weekly for 7 consecutive weeks. The results demonstrated that the addition of the three mentioned pesticides significantly decreased the microbial activities and counts of soil bacteria, fungi and actinomycetes. The observed effect was depended upon the type and amount of pesticide as well as the length of incubation period. The microbial activities and the number of bacteria, fungi, and actinomycetes were inversely proportional to the concentration of pesticides added to the soil. In most treatments, soil samples treated with 200ppm of Malathion demonstrated the lowest microbial activities and counts of bacteria, fungi and actinomycetes. This study suggests that the investigated pesticides negatively affect microbial counts and activity in soil, which confirms and reinforces previously reported environmental concerns.