In eroded landforms, soil properties that influence herbicide fate are highly variable with landscape position. Understanding the variation in herbicide sorption and dissipation is essential to characterize weed control efficacy and availability for off-site transport. We evaluated the sorption and/or dissipation of four herbicides in surface soils from an eroded prairie landform. Soil organic carbon in the eroded upper slope was about half that in the depositional lower slope. Sorption of saflufenacil, aminocyclopyrachlor, and picloram was on average 3-5 times higher in the lower slope than in the upper slope. For these herbicides, sorption coefficients were less variable when normalized to the fraction of organic carbon. Metolachlor showed the same sorption in soils from these landscape positions, despite the large difference in soil properties. Dissipation proceeded at approximately the same rate in both soils. Results emphasize the need for compound- and soil-specific information to enable accurate predictions of pesticide fate.

Spatial variation in sorption and dissipation is herbicide dependent

244th National Meeting (2012)

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