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Influence of organic matter and pH on bentazone sorption in soils

Li, K., Liu, W., Xu, D., Lee, S.
Journal of agricultural and food chemistry 2003 v.51 no.18 pp. 5362-5366
bentazon, herbicide residues, sorption, sorption isotherms, soil organic matter, humic acids, soil pH, octanol-water partition coefficients, sandy soils, clay loam soils, sandy loam soils, paddy soils, equations, mathematical models, loamy sand soils
Bentazone (3-isopropyl-1H-2,1,3-benzonthiadiazain-(4)3H-one 2,2-dioxide) is a postemergence herbicide which is used extensively worldwide, especially in China. The sorption of bentazone in various types of soils and extracted humic acids was investigated using a batch equilibration technique. Significant linearity was observed in sorption isotherms in five different types of soil, with distribution coefficients (Kd) that varied between 0.140 and 0.321 mL g-1. The distribution coefficient was determined to be a function of organic matter and pH in the soil. A model based on distribution coefficients was developed to predict bentazone sorption in soils. The organic matter-normalized partition coefficients for the neutral and anionic forms of bentazone were 370.3 and 2.40 mL g-1, respectively. Hence, more attention should be given to the potential leaching problem when bentazone is applied in soils containing low organic matter and high pH.