Effects of selected synthetic and biological insecticides on microbial population and microbial activities of soil samples

Abstract

Modern agriculture depends upon the wide variety of natural and synthetically producedchemicals such insecticides, fungicides, herbicides, and other pesticides. This work studied the effect ofsynthetic and biological insecticides on microbial population and microbial activities in soil samples. Theinsecticides used in this study are cypermethrin, chlorpyrifos, neem extracts, and ginger extracts. Bacteriaand fungi were isolated and identified from the soil samples. TBC, TCC, and TFC were determined.Dehydrogenase activity, microbial respiration, and microbial biomass carbon in the soil samples were alsoexamined. The control soil samples recorded the highest TBC, TFC, TCC, dehydrogenase activity, microbialrespiration, and microbial biomass carbon. Soils treated with chlorpyrifos recorded the lowest total coliformcount of 0.10×105 ± 0.00 cfu/g, while cypermethrin treated soils recorded the lowest total bacterial count of0.58×105 ± 0.025 cfu/g. Cypermethrin-treated soils had the lowest effect on CO2 respired in the soil with avalue of 1687.50 ± 1.500 mg/kg. 500 g/mL Neem leaf extract had the highest microbial biomass carbonvalue of 9.40 ± 0.100 kgC/m2. This work has shown that treatment with both synthetic and bio-insecticidesresulted in significant drop in microbial population and microbial activity of soil samples.