Residues of ~(14)C-metsulfuron-methyl in Chinese paddy soils

摘要

BACKGROUND:Metsulfuron-methyl is widely used for controlling many annual grasses and broadleaf weeds in cereal crops.Nonetheless,increasing evidence has demonstrated that even extremely low levels of metsulfuron-methyl residues in soil can be toxic to subsequent crops or non-target organisms.The behavior of herbicides in soils is mostly related to their residual forms.The intent of the present study was to investigate the dynamics of extractable residues(ERs)and non-extractable residues(NERs)of ~(14)C-metsulfuron-methyl in twelve Chinese paddy soils and their relationships to soil properties.RESULTS:ERs decreased gradually after application,whereas NERs increased rapidly during the initial 28 days,and gradually decreased thereafter.ERs and NERs were respectively 10.1-67.9% and 5.6-28.7% of applied radioactivity in soils at 224 days after application.ERs correlated positively with soil pH and silt fractions,and negatively with microbial biomass carbon(MBC)and clay fractions,but the opposite was observed for NERs.CONCLUSION:Both ERs and NERs may be present in the soil at the time of planting following rice crops,and the risk of phytotoxic effects needs to be considered.Soil pH,MBC and clay/silt fractions were the main factors in affecting the amounts of both ERs and NERs of metsulfuron-methyl in the tested soils.