Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2004
Publication Date: 10/31/2004
Citation: Gish, T.J., Prueger, J.H., McConnell, L.L., Kustas, W.P., McKee, L.G., Hatfield, J.L. 2004. Factors influencing watershed scale pesticide volatilization [abstract]. 68th Annual Meeting of the Soil Science Society of America. 518:287.
Technical Abstract: To effectively evaluate the fate of agricultural chemicals, surface and subsurface processes must be simultaneously evaluated at the field scale. Fundamental to the quantifiation of pesticide field behavior is the impact of soil type, management practice, pesticide chemistry, and climate on pesticide volatilization fluxes to the atmosphere. A five year study at the Optimizing Production inputs for Economic and Environmental Enhancement project (OPE3), Beltsville, MD was designed to evaluate the impact of climate on the field scale behavior of the pre-emergent herbicides atrazine and metolachlor. Herbicide vapor concentrations were measured using polyurethane foam plugs at five heights above the soil surface. Pesticide volatilization fluxes were computed using concentration profiles with a flux gradient technique and corresponding eddy covariance measurements. Although soil type, pesticide chemistry, and management were the same for the five year period, cumulative pesticide volatilization losses across years varied from 5 to 25% of that applied. Furthermore, pesticide volatilization increased exponentially with soil water contents > 20%. In addition, about 90% of pesticide vapor loss occurred within the first 72 hours. These results suggest that climatological impacts, i.e. rainfall timing on surface soil moisture relative to pesticide application, was the most critical factor influencing pesticide loss to the atmosphere.