Effects of the herbicide alachlor on soil microbial activities.

: A study was made of the effects of one selected acetanilide herbicide, alachlor, at concentrations of 2.0-10.0 kg ha(-1) on bacterial populations, fungi, dinitrogen fixation bacteria, denitrifying bacteria, nitrifying bacteria, nitrogenase activity, acid and alkaline phosphatases, arylsulfatase and deshydrogenase. The presence of 2.0-10.0 kg ha(-1) of alachlor in the soil increased the total number of bacteria and fungi. The population of denitrifying bacteria increased significantly at concentrations of 5.0-10.0 kg ha(-1). However, aerobic dinitrogen fixing bacteria and nitrogenase activity decreased at alachlor concentrations of 3.5-10.0 kg ha(-1). Acid and alkaline phosphatases, arylsulfatase and dehydrogenase activity decreased significantly initially at concentrations of 5.0-10.0 kg ha(-1), but recovered to levels similar to those in the control. Nitrifying bacteria were not affected as a consequence of the addition of the herbicide to agricultural soil.