Effect of Malathion on Microbial Population, Acid and Alkaline Phosphatase Activity of Soil

In this study the response of microbial populations, acid and alkaline phosphatase activities of microorganisms in garden soil after incorporation of the pesticide Malathion [S-1, 2-bis (ethoxycarbonyl) ethyl O, O-dimethyl phosphorodithioate] were examined. The effect of malathion was observed over a period of ten days in three different concentrations each viz. , 1 %, 0.5 % and 0.2 %. Total microbial count was highly affected in presence of malathion and persisted up to 7 days when the population of soil microbes was found to be highest in untreated soil sample (7.55x10^6 cells per gram of soil) followed by samples having 0.2 % (6.2x10^6 cells per gram), 0.5 % (1.4x10^6 cells per gram) and undiluted concentrations (0.6x10^6 cells per gram) of the pesticide. Phosphatase activity in soil was unaffected initially (up to 3 days) and then sharply decreased on day 7 with 10.359g/g/hr, 15.263g/g/hr, 14.44g/g/hr and 10.144g/g/hr of p-nitrophenol in control, 1 %, 0.5 % and 0.2 % concentrations of malathion treated soil respectively.