Alteration of certain soil microbiological and biochemical indices of a paddy soil under anthropogenic stress

A 21-day laboratory incubation experiment was conducted to investigate the impact of pesticides (insecticide, herbicide, fungicide) on paddy field soil health under omatrolld moisture (flooded soil) and tem-perature (25℃ ) environment. The electron system (ETS)/Dehydrogenase activity showed negative correlation with pesticides concentrations, decreased with increase of pesticide ooncentration. The higher doses (5 to 10 times field rates) of pesticides significantly inhibited ETS activity, while lower rates failed to produce any significant reducing effect on the control. The toxicity of pesticides in decreasing the ETS activity was in the order: insectidde > fungicide > herbicide, irrespective of their rates of application. The pasticides increased the soil phenol content, which increased with increasing concentration of agrochemicals. The pesticide applieatkm did not produce any significant change in soil protein content. The response of biomamess phospholipid content was nearly similar to that of ETS activity. The phospholipid content decreased with the addition of pesficides in the order insecfidde > furgicide > herbicide and the maidty was in the order: 10 FR (field rate) > 5FR> 1.0 FR > 0.5 FR >control.