Microbial degradation of penoxsulam in flooded rice field soils.
The degradation of penoxsulam [2-(2,2-difluoroethoxy)-N-5,8-dimethoxy[1,2,4]triazolo[1,5-C]pyrimidin-2-yl-6-(trifluoromethyl)benzene-sulfonamide] was studied in flasks simulating flooded rice field conditions using four representative rice field soils from the Sacramento Valley. Degradation half-lives (t(1/2) values) ranged between 2 and 13 days. Increased degradation rates were observed in flask systems with steeper redox gradients between the flooded soil layer and the overlaying water. Two transient metabolites were identified that were temporarily formed in amounts exceeding 5% of the total initial mass of penoxsulam. The results of high-performance liquid chromatography/(14)C radiodetection studies indicate that the degradation of the triazolopyrimidine system and its substituents is the main pathway of microbial transformation processes. Microbial activity, as measured by dehydrogenase activity, was not affected by penoxsulam concentrations corresponding to the proposed maximum annual use rate of 40 g active ingredient/ha.
Jabusch
Thomas W
TW
Department of Environmental Toxicology, College of Agricultural and Environmental Sciences, University of California, Davis, 95616-8588, USA. thomasj@sfei.org
Tjeerdema
Ronald S
RS
D001419:Bacteria / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D006540:Herbicides / Q000378:metabolism*; D007700:Kinetics; D012275:Oryza / Q000254:growth & development*; D010088:Oxidoreductases / Q000378:metabolism; D012988:Soil Microbiology; D013449:Sulfonamides / Q000378:metabolism*; D014529:Uridine / Q000031:analogs & derivatives* / Q000378:metabolism
D002250:Carbon Radioisotopes; D006540:Herbicides; D013449:Sulfonamides; C504402:penoxsulam; D010088:Oxidoreductases; D014529:Uridine