Ultimate fate of halosulfuron methyl and its effects on enzymatic and microbial activities in three differently textured soils

Halosulfuron methyl is a sulfonylurea herbicide used worldwide for weed control in sugarcane, maize, wheat, and rice production. Considering its environmental impact, this study evaluated the effects of soil type, application rate, and temperature on the dynamics of halosulfuron methyl degradation. Additionally, as soil microbes and enzymes are reliable indicators of the impacts of anthropogenic activities on soil health, the effects of halosulfuron methyl on soil enzymatic and microbial activities were also assessed. The half-life (DT₅₀) of halosulfuron methyl varied from 9.38 to 33.77 d. Increase in temperature accelerated the degradation and DT₅₀ varied from 14.39 to 33.77, 11.05 to 28.94, and 9.38 to 25.41 d at 5, 15, and 25 °C, respectively. The metabolites of halosulfuron methyl, including halosulfuron, methyl 3-chloro-5-((4,6-dimethoxy-2-pyrimidinyl) amino)-1-methyl-1H-pyrazole-4-carboxylate, 4,6-dimethoxy-2-pyrimidinamine, and methyl 3-chloro-1-methyl-5-sulfamoyl-1H-pyrazole-4-carboxylate, were detected in the studied soils, and their appearance and disappearance varied with application rate, soil type, and incubation temperature. Halosulfuron methyl had transitory harmful effects on soil enzymatic and microbial activities depending on its application rate. The results suggest that the application rate of halosulfuron methyl, soil physicochemical parameters, and temperature should be considered together to ensure satisfactory weed control with reduced environmental risk.