Field Dissipation of Cloransulam-methyl at Four Sites in the U.S. Soybean Market

Abstract

The soil dissipation of cloransulam-methyl was studied using 14C-labeled and non-radiolabeled material in Wisconsin, Indiana, Mississippi, and North Carolina between 1993 and 1995. The test substance was pre-emergence broadcast-applied at target rates of 50 and 61.5 g ai ha-1 for the 14C-labeled and the non-radiolabeled studies, respectively. Bromide was used to track water movement at the NC and WI sites. The degradation of cloransulam-methyl was rapid and best characterized by a two-compartment model resulting in initial-rate half-lives ranging from 2.5 to 4.8 days at the MS, IN, and WI sites and by a first-order degradation model at the NC site with a half-life of 11.2 days. The rapid dissipation rates, metabolite formation patterns, and sorption characteristics obtained in this field study were consistent with the existing laboratory data generated for cloransulam-methyl. Rapid degradation rates and the increasing sorption to soil over time resulted in low persistence and mobility of this compound. Keywords: Cloransulam-methyl; triazolopyrimidine sulfonanalide; soil dissipation