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Title: Mineralization of metsulfuron-methyl in Chinese paddy soils

Author
item WANG, H - ZHEJIANG UNIV, CHINA
item XU, J - ZHEJIANG UNIV, CHINA
item Yates, Scott
item ZHANG, J - CHINESE ACDMY OF SCIENCE
item GAN, J - UC RIVERSIDE, CA
item MA, JINCAI - University Of California
item WU, J - ZHEJIANG UNIV, CHINA
item XUAN, RICHENG - University Of California

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2009
Publication Date: 1/1/2010
Citation: Wang, H.Z., Xu, J.M., Yates, S.R., Zhang, J.B., Gan, J., Ma, J., Wu, J.J., Xuan, R. 2010. Mineralization of metsulfuron-methyl in Chinese paddy soils. Chemosphere. 78(3):335-341.

Interpretive Summary: Use of herbicides in rice production systems has the potential to injure subsequent crops due to the effect of seasonal carry over. Metsulfuron-methyl is one of the most commonly used herbicides in rice production. Many soil and environmental factors affect the length of time the chemical remains in soil and the potential for crop injury. In this study, the effects of moisture content, pH, organic carbon content, and microbial biomass were studied for several soils commonly used in rice production. Overall, the transformation of metsulfuron-methyl into harmless chemical compounds took longer at 15oC than at higher temperatures. Further, the mineralization rate was found to be highly dependent on soil pH. This study provides information that will assist rice growers in managing herbicides to protect environmental resources and to protect crops from injury due to herbicide residues remaining in soils into the next season’s planting.

Technical Abstract: A laboratory study was conducted to investigate the mineralization of metsulfuron-methyl (MSM) in paddy soils in response to soil moisture, temperature and soil properties. The results indicated that MSM mineralization was relatively limited in the paddy soils when soil temperature was low. Only 2.2–6.0% of the applied 14C mineralized after 84 d of incubation at 15C. The mineralization of MSM was enhanced by increasing soil moisture and soil temperature. Soil moisture would have different impact on the response of MSM mineralization to variation in soil temperature. An increase of 10C accelerated the average rate of MSM mineralization by 2.3 times at 50% water-holding capacity (WHC) and 1.9 times at 40% WHC. Regression analysis showed that soil pH, organic carbon contents, microbial biomass carbon contents, and silt/clay fractions were the dominant factors affecting MSM mineralization, with pH as the most important factor. The relatively slow mineralization rate of MSM suggested long persistence of this herbicide in soil, thus increasing its potential ecological risk, especially when applied in alkaline soils and in cold areas.