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Title: EFFECT OF MOISTURE AND TEMPERATURE ON DEGRADATION OF ISOXAFLUTOLE IN SOIL

Author
item TAYLOR-LOVELL, SARAH - UNIV OF ILLINOIS
item Sims, Gerald
item Wax, Loyd

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/20/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The degradation and transformation of a soil-applied herbicide in the soil are important in understanding the activity and environmental behavior. Isoxaflutole is a new corn herbicide which exhibits several unique characteristics in the soil. The parent, isoxaflutole, is not bioactive, but must be transformed to diketonitrile, the active metabolite. Effective weed control with the herbicide is dependant on adequate moisture following application, potentially due to hydrolysis of isoxaflutole to diketonitrile. Degradation of radiolabeled isoxaflutole was measured over time in soil biometers with a CO2 trap to determine mineralization. The effect of moisture was determined by maintaining the soil at air dry, 1.5 MPa, 0.1 MPa, or air dry followed by 0.1 MPa. Temperature effects were examined using soils stored at 5, 15, 25, and 35 C throughout the study. LSC was used to quantify the concentration of radiolabeled material mineralized, sorbed, or bound in the biometers. Transformation of isoxaflutole to diketonitrile and other metabolites in the sorbed phase was measured with TLC. The degradation of isoxaflutole and diketonitrile was found to be more rapid in the high moisture environments and with increasing temperature. Over time, a large portion of the herbicide became bound, or unextractable, particularly in the dry soil. The majority of this radioactivity was accounted for by oxidizing the soil. This information can be used to develop a greater understanding of the efficacy and environmental fate of isoxaflutole.