Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2004
Publication Date: November 18, 2004
Citation: Rice, P.J., Koskinen, W.C., Carrizosa, M. 2004. Effect of soil properties on the degradation of isoxaflutole and the sorption-desorption of isoxaflutole and its diketonitrile degradate. Journal of Agricultural and Food Chemistry. 52:7621-7627. Interpretive Summary: The present study was conducted to determine the influence of soil characteristics (pH, clay content, and organic carbon content) on the degradation of a relative new herbicide isoxaflutole and the sorption and desorption of isoxaflutole (ISOX) and its main degradate, DKN. The degradation of ISOX to DKN was rapid. At 24h the solution phase concentrations of ISOX and DKN were similar, suggesting the 24-h sorption coefficients (Koc) for ISOX treated soils are actually a Koc for mixed ISOX residues. Greatest sorption of ISOX residues and DKN was observed in the soil with the lowest pH, while the soil with the least sorption had the lowest clay content. These results will be of benefit/interest to farmers, extension agents and scientist. The persistence and availability of pesticide residues in soil will impact their potential movement from an area of application to surrounding surface water or ground water. Understanding factors that influence the persistence and bioavailability of ISOX and DKN in soil will allow for more accurate prediction of their environmental fate.
Technical Abstract: Sorption-desorption of isoxaflutole (ISOX) and a diketonitrile degradate (DKN) were characterized in five soils with different clay and organic carbon contents and soil pH. Sorption fit the Freundlich equation with sorption minimally dependent on herbicide concentration. ISOX and DKN sorption was immediate; 95% of the sorption occurred within 2 h. Characterization of the CaCl2 solution revealed ISOX degradation was rapid in the CaCl2/soil systems.Solution phase ISOX and DKN concentrations were similar at 24 h, suggesting the 24-h sorption coefficients (Koc) for 14C-ISOX treated soils are actually a Koc for mixed ISOX residues. For the five soils, Koc of ISOX residues ranged from 24.8 to 85.3 while the Koc for DKN ranged from 8.17 to 22.2. Greatest sorption of ISOX residues and DKN was observed in the soil with the lowest pH (5.69), while the soil with the least sorption had the lowest clay content (12.3%).