This study was conducted to determine the effects of pesticide application on soil microbial spectrum using a herbicide (Glyphosate; the active ingredient in Roundup) and an insecticide (Chlorpyrifos). The control soil samples had no pesticide application. Soil samples taken at the depth of 0-20cm from the Biological Garden was taken to the laboratory. The soil was sieved through a 2mm mesh to remove stones and plant debris. One kilogram of the soil samples was weighed and transferred into different containers into which 150ml of the dissolved pesticides were applied. The numbers of colony forming units (CFU) of respective groups of microorganisms were determined on Nutrient Agar and Sabouraud Dextrose Agar media by pour plate method. After 1, 7, 14 and 21 days of experiment, the number of bacteria and fungi were estimated. At the end of the study, results revealed that pesticide applications caused reduction in microbial population present in the soil when compared with the control. Also, despite the reductions, bacterial species like Bacillus subtilis developed tolerance possibly due to its characteristic spore formation, others like Pseudomonas aeruginosa disappeared immediately after pesticide treatment only to reappear and start multiplying after some days. This may be due, in part, to evolution and development of metabolic mechanisms to use the pesticides as a carbon and energy source. Using a paired t-Test, calculated value of 14.9 for Glyphosate and 24.1 for Chlorpyrifos is greater than t-tabulate value at 0.05 confidence level, indicating that there is a great difference between microbial population in pesticide treated soil and non-treated soil confirming the effects of microbial population reduction and possible extinction due to pesticide application on the soil.
© Journal of Scientific and Engineering Research
Frontier Theme