Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 1996
Publication Date: N/A
Interpretive Summary: Bentazon is a postemergence herbicide useful in the control of broadleaf and sedge weeds in soybeans under no-tillage (NT). Laboratory studies determined degradation of this herbicide in two soils from Mississippi and three soils from Illinois under conventional-tillage (CT) and no-tillage (3 to 18 years) with varying histories of bentazon application (0 to 9 applications). Bentazon is short-lived (half life of 1-2 weeks) in soils that have had previous exposure. Furthermore, soils with a long history of bentazon application have greater ability to degrade it under NT than under CT. Bentazon is primarily degraded to products that are rapidly incorporated into soil organic matter, although a significant amount is degraded to carbon dioxide. These results provide evidence that the bentazon persistence in soils is affected by soil management practices, such as no-tillage.
Laboratory studies determined the fate of bentazon (3-isopropyl-1H- 2, 1, 3 benzothiadiazin-4(3H)-one-2, 2-dioxide) in soil as affected by tillage and history of application. Bentazon degradation in two soils from Mississippi and three soils from Illinois under conventional-tillage (CT) and no-tillage (NT) (3 to 18 years) with varying histories of bentazon application (0 to 9 applications) was studied. The half-life (DT50) for bentazon degradation ranged from 6.7 to 49.5 d; half-lives for NT of the two soils with the longest history of bentazon application were significantly lower than CT. Dissipation of bentazon was accompanied with increases in non- extractable material. Methyl bentazon was the most consistently observed metabolite (1.7 to 5.8% applied 14**C after 48 d). Bentazon mineralization ranged from 12 to 18% applied after 48 d and 2 to 3% applied after 22 d for bentazon history and non-history soils, respectively. Mineralization was affected by tillage in the two of the five soils with the longest bentazon history.