EFFECTS OF THE HERBICIDE IMAZETHAPYR ON SOIL MICROBIAL BIOMASS AND VARIOUS SOIL ENZYME-ACTIVITIES

The effects of imazethapyr, an imidazolinone derivative on the soil mi crobial biomass was investigated in a clay loam soil. Imazethapyr was applied in a field trial at the recommended field rate for soybean wee ding, 50 g a.i. ha-1. In laboratory experiments the herbicide was inco rporated at the field rate and 10-fold and 100-fold higher. In both th e field trials and the laboratory experiments, the field rate of imaze thapyr had no adverse effects on the microbiological processes tested. But at 10-fold and 100-fold higher rates, the herbicide decreased the biomass-C content and dehydrogenase activity and increased the hydrol ytic capacity and protease and catalase activity. These findings sugge st that there may be a risk in monocultural practices that require rep eated herbicide treatments.