EFFECT OF AN ORGANOPHOSPHORUS INSECTICIDE, PROFENOFOS, ON AGRICULTURAL SOIL MICROFLORA

A study was made of the effects of insecticide profenofos at concentrations of 10, 50, 100, 200 and 300-mu-g per gram of soil on total bacteria populations, fungi, dinitrogen fixer, denitrifying bacteria, nitrifying bacteria (phase I and II) and nitrogenase activity (C2H2 reduction) in an agricultural soil. The presence of 10 to 300-mu-g/g significantly increased the total number of bacteria and denitrifying bacteria. However, the population of aerobia dinitrogen fixing bacteria and dinitrogen fixation were suppressed significantly. Nitrifying bacteria and fungal populations decreased initially at concentrations of 100 to 300-mu-g/g but recovered rapidly to levels similar than those in the control.