Effect of pesticides on biochemical properties of tomato (Solanum lycopersicon) cropped soil

Abstract

A study was conducted during 2006–08 on the effect of pesticides (mancozeb, endosulfan and chlorpyrifos) on tomato (Solanum lycopersicon L.) cropped soil for total microbial population, symbiotic and asymbiotic nitrogen bacterial counts and microbial activities. The physico-chemical soil properties were not affected by pesticide applications, however, the viable microbial counts were reduced drastically even at lower concentrations of applied pesticides. All pesticides had moderate to high inhibitory effect on phosphatase and dehydrogenase activity, though the effect of chlorpyrifos was most persistent. Chlorpyrifos at 100 mg/kg inhibited more than 35 and 50% activity of dehydrogenase and phosphatase enzymes, respectively, even after 35 days of treatment. Mancozeb was highly toxic at the initial stage, inhibiting 90% dehydrogenase and 65% phosphatase activity within 7 days of treatment at 100 mg/kg. The microbial respiratory activity was also highly affected in the presence of all the pesticides at 50 and 100 mg/kg levels. After 1 day of pesticide treatment, CO2 evaluation was minimum (1 mg CO2/50 g soil) in mancozeb.