Sorption Characteristics of Benzobicyclon Hydrolysate in Important Rice-Production Soils.

Soil sorption is a key process controlling the environmental fate and transport of herbicides, and varies with soil properties such as clay content, organic matter, and pH. Arkansas is the top rice producer in the United States, with production occurring on a wide range of soils. Information regarding the soil sorption of benzobicyclon hydrolysate, the active herbicidal compound in a new rice herbicide formulated as Rogue (Gowan Company, pending registration), is completely lacking in the peer-reviewed literature for soils important for rice production in the United States. In order to understand how herbicides will behave in soils used for Arkansas rice production, representative soil series from the top 15 rice-producing counties in Arkansas will be collected for use in laboratory-based sorption experiments. Soil from 0-10 cm depth will be air-dried, ground, and sieved to 2 mm prior to experiments. Physical and chemical soil properties including soil texture, percent organic matter, CEC, and pH will be analyzed. Benzobicyclon hydrolysate sorption experiments will be conducted over a range of initial aqueous phase concentrations. Mixtures of fixed solid to solution ratio will be agitated for 16 hours at constant temperature. Supernatant will be analyzed and quantified using high-performance liquid chromatography (HPLC) with diode array detection (DAD). Regression of sorption data and soil properties will be carried out to further understand the interaction between soils and herbicides, and sorption isotherms will be developed. Describing and quantifying the interaction between herbicides and soil will inform the development of agricultural practices that prevent off-site movement into surface and ground water and enhance the efficacy of the herbicide.