Submitted to: Pest Management Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/31/2008
Publication Date: 5/27/2008
Publication URL: www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2255.pdf
Citation: Wang, H., Xu, J., Wu, J., Yates, S.R., Gan, J. 2008. Residues of 14C-metsulfuron-methyl in Chinese Paddy soils. Pest Management Science. 64:1074-1079. Interpretive Summary: The increasing use of herbicides has created serious concerns about the adverse effects of herbicide residues on the surrounding environment, agricultural production systems and human health. To evaluate the potential impact of soil herbicide residues on crop production and environmental quality, it is necessary to distinguish between extractable and non-extractable residues in soil. Metsulfuron-methyl is a sulfonylurea herbicide used worldwide for controlling broad-leaf weeds in cereals, has high herbicidal activity, low mammalian toxicity and can be applied at low application rates. Nearly 50% of the applied material is still present in soil some 4-5 months following application, so carry-over into succeeding crops is also of particular concern. The purpose of this research was to study the degradation and persistence of metsulfuron-methyl in soil and to determine the ease of extracting this pesticide various times after application. Understanding the behavior of sulfonylurea herbicides in soil with help growers utilize this material more effectively while continuing to protect the environment.
Technical Abstract: 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 were toxic to the 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 (ER) and non-extractable residues (NER) of 14C-metsulfuron-methyl in twelve Chinese paddy soils and their relationships to soil properties. ER decreased gradually after application, whereas NER increased rapidly during the initial 28 days, and gradually decreased afterward. ER and NER were 10.1%~67.9% and 5.6%~28.7% of applied radioactivity in soils at 224 days after application, respectively. ER was correlated positively with soil pH and silt fractions, and negatively correlated with microbial biomass carbon (MBC) and clay fractions, while the opposite was observed for NER. There is a potential risk for both ER and NER to cause toxicity to rice grown in the following season. Soil pH, MBC and clay/silt fractions were the main factors in affecting the amounts of both ER and NER in the tested soils.