Degradation of nicosulfuron in soil

Abstract

Nicosulfuron (2-[[[[(4.6-dimethoxy-2-pyrimidinyl]amino] carbonylJamino]|sulfony!]-N,Ndimethyl-3-pyridinecarboxamide) is a sulfonylurea herbicide (SU) used for selective postemergence control of annual and perennial grasses in corn. In contrast to traditional herbicides used in corn that are applied at rates >1 kg ha’', nicosulfuron is typically applied at rates <100 g ha’', Because of the low application rates, it has been thought to have a lower potential for contamination of surface and ground waters than other traditional corn herbicides [1]. Degradation of the herbicide nicosulfuron in three samples of soil was investigated under laboratory conditions. Degradation of nicosulfuron in soils was pH-dependent; calculated half-life (t;2) values ranged from 0.37 to 9.11 days. Nicosulfuron was more persistent in neutral or weakly basic soil than in acidic soil. The degradation pathways included the cleavage of the sulfonylurea bridge to form the pyridine sulfonamide and pyrimidine amine, and hydrosylation on the pyrimidine ring were the main metabolic pathways.