Effect of metolachlor on azotobacter nitrogen fixation in soil

Abstract The effect on nitrogen fixation of 100, 200, 300, 400 and 500 μg metolachlor per gram of soil was studied in nonsterile soil incubated under aerobic conditions and sterilized soil inoculated with Azotobacter chroococcum. Metolachlor at concentrations of 400 and 500 μg/g significantly reduced dinitrogen fixation in nonsterile soil and sterile soil inoculated with Azotobacter sp. However, this inhibitory effect on nitrogenase activity disappeared after 24 h, showing that acrobic diazotrophs populations present in the soil can tolerate high concentration of this herbicide without significant changes in their nitrogenase activity.