Environmental fate of fall-applied metolachlor
Date
1997
Authors
Jiang, Shuguang
Major Professor
Advisor
Baker, James L.
Committee Member
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Abstract
Changing some metolachlor applications from spring to fall within a watershed could result in lower herbicide concentrations and losses with spring runoff events by reducing the total herbicide available in the surface soil for runoff during the spring season, in part by degradation over the winter. In addition, applying metolachlor in the fall would allow a shallow incorporation of the herbicide into the soil matrix through diffusion and with fall rainfall events that typically are less intense than spring/early summer storms, thus possibly reducing herbicide availability for surface runoff at the field scale. However, with fall application, runoff losses with snowmelt are possible. This study in the first two years (94-95 and 95-96) provided quantitative research data on the potential of fall application to reduce metolachlor surface runoff concentrations and losses from the field. Beginning in the fall of 1996, the research site was used to study the effects of soil incorporation on herbicide persistence and runoff loss for the fall-applied metolachlor. The objectives of this research were the following: to determine relative edge-of-field runoff concentrations and losses of fall- and spring-applied metolachlor with water and sediment in snowmelt and rainfall-runoff, to monitor with time the relative amounts and location of fall- and spring-applied metolachlor in four layers in the top 35 cm of the soil profile, to study the potential of metolachlor loss by volatilization and photolysis, and to investigate the effects of soil incorporation on metolachlor soil persistence and runoff loss (with water and sediment in snowmelt and rainfall-runoff).
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thesis