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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #203920
Title: Role of Sorption and Degradation in the Herbicidal Function of Isoxaflutole

Author
item Sims, Gerald
item TAYLOR-LOVELL, SARAH - UNIV OF VERMONT
item TARR, GABE - UNIV OF ILLINOIS
item MASKET, SHAWN - UNIV OF ILLINOIS

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2009
Publication Date: 7/1/2009
Citation: Sims, G.K., Taylor-Lovell, S., Tarr, G., Masket, S. 2009. Role of Sorption and Degradation in the Herbicidal Function of Isoxaflutole. Pest Management Science. 65(7):805-810.

Interpretive Summary: The fate of isoxaflutole in soil is closely tied to soil sorption. Herein, the sorption and transformation isoxaflutole was investigated in laboratory incubations and these results were used to interpret greenhouse studies on control of several weed species. In soil, isoxaflutole was hydrolyzed to form a diketonitrile derivative, which is the active form of the herbicide. The diketonitrile was then metabolized to the inactive benzoic acid derivative, and two unknown products were formed in small quantities in the later part of the study. Transformation to diketonitrile, an abiotic reaction, was initially very rapid and occurred at similar rates in all soils. However, the transformation rate of DKN to BA, a biological process, varied between the different soils, the rate of which appeared to be inversely related to the fraction of added radiocarbon that remained unextractable. Control of most weed species appeared to be a function of both sorption and biodegradation, with greatest weed control being observed in soils in which a significant portion of the active herbicide remained and sorption was limited.

Technical Abstract: The fate of isoxaflutole in soil is closely tied to soil sorption. Herein, the sorption and transformation isoxaflutole was investigated in laboratory incubations and these results were used to interpret greenhouse studies on control of several weed species. In soil, isoxaflutole was hydrolyzed to form a diketonitrile derivative, which is the active form of the herbicide. The diketonitrile was then metabolized to the inactive benzoic acid derivative, and two unknown products were formed in small quantities in the later part of the study. Transformation to diketonitrile, an abiotic reaction, was initially very rapid and occurred at similar rates in all soils. However, the transformation rate of DKN to BA, a biological process, varied between the different soils, the rate of which appeared to be inversely related to the fraction of added radiocarbon that remained unextractable. Control of most weed species appeared to be a function of both sorption and biodegradation, with greatest weed control being observed in soils in which a significant portion of the active herbicide remained and sorption was limited.