Effect of fly ash amendment on persistence of metribuzin in soils.

This study reports the effect of fly ash amendment on persistence of metribuzin in three Indian soil types. Fly ash [Inderprastha (IP) and Kota] was amended at 1, 2 and 5% levels. Metribuzin was more persistent in the flooded soils (predominantly anaerobic) than the nonflooded (aerobic) soils. Kota fly ash amendment to nonflooded soils slightly enhanced metribuzin persistence while IP fly ash reduced the herbicide persistence in nonflooded soils. In flooded soils both types of fly ash reduced metribuzin persistence, but the extent of the effect was specific to the soil and type of fly ash. A better effect was observed in low organic matter soils and IP fly ash was more effective than the Kota fly ash. The effect of fly ash amendment on metribuzin degradation in soils was more pronounced at higher dose of fly ash. No degradation of metribuzin was observed in the sterilized soils, both without and with fly ash, suggesting that degradation of metribuzin was microbial in nature. Deaminometribuzin was recovered as the only metabolite of metribuzin degradation.