The effects of moisture and temperature on the degradation of sulfentrazone

This study examined the degradation of sulfentrazone in Arenic Hapludult soil, such soil being representative of regions where sulfentrazone is used in Brazil. Soil samples were supplemented with the herbicide [0.7 mu g active ingredient (a.i.) g(-1) soil] and maintained at 27 degrees C. The soil moisture content was corrected to 30, 70 or 100% of water holding capacity (WHC). Herbicide-free soil samples were used as controls. Aliquots were taken after 14, 30. 60, 120, 180 and 255 days of incubation for the quantitative analysis of sulfentrazone residues by gas chromatography. Another experiment was conducted using soil samples with and without herbicide, submitted to different temperatures of 15, 30 and 40 degrees C, and kept at a constant value for WHC of 70%. The sulfentrazone residues were quantified by gas chromatography after 14, 30, 60 and 120 days of incubation. The potential degrader microorganisms were isolated and identified. A half-life of 172.4 days was estimated at 27 degrees C and 70% WHC. The microorganisms identified as potential degraders of the herbicide were Acinetobacter calcoaceticus, Chrysosporium sp., Eupenicillium sp., Metarhizium sp. and Paecilomyces sp. After 120 days, temperature had no further effect (P<0.16) on sulfentrazone degradation, and the soil moisture content had no effect on degradation at any time. (C) 2008 Elsevier B.V. All rights reserved.