DEVELOPMENT OF ALTERNATIVE PRACTICES FOR IMPROVED WATERSHED MANAGEMENT
Location: Cropping Systems and Water Quality Research
Title: Herbicide Transport to Surface Runoff on Claypan Soils: Scaling from Plots to Fields
Submitted to: Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: January 19, 2010
Publication Date: July 11, 2010
Citation: Ghidey, F., Baffaut, C., Sadler, E.J., Lerch, R.N. 2010. Herbicide Transport to Surface Runoff on Claypan Soils: Scaling from Plots to Fields [abstract]. Soil and Water Conservation Society Annual Conference; July 18-21, 2010, St. Louis, Missouri. Available: http://www.swcs.org/documents/filelibrary/10ac/2010_Oral_Presentation_Abstracts_566DF5164F928.pdf.
The offsite movement of herbicides into streams and lakes is a serious non-point source pollution problem. Claypan soils, which have a significant runoff potential because of low permeability, are especially susceptible to soil and herbicide losses. Previous plot scale (0.92 ac) monitoring showed that herbicide losses from a corn-soybean rotation under a no-till tillage system without any incorporation were higher than from a mulch tillage system with incorporation. Exponential models that calculate average event herbicide concentrations as a function of application rate, runoff volume, days after application, and cumulative temperature had been developed using plot scale data. Model proportionality coefficients for the no-till system were four to five times higher than for the mulch-till system. The objective of this study was to extend these results to the field scale. Two fields (85 and 19 ac) were instrumented during 1997-2001, and runoff and associated herbicide losses were measured during each runoff event. The applicability of the exponential model was tested at the field scale. The models developed at plot scale performed well in calculating atrazine concentrations at field scale, as indicated by r2 and the Nash-Sutcliffe efficiency greater than 0.7 and 0.64, respectively. These findings indicate that the results obtained on replicated plots can be extended to the field scale. They confirm that, on claypan soils, not incorporating herbicides, as would be done in a no-till system, leads to significantly higher herbicide losses. The challenge is to find a management system that keeps herbicides in the soil when no-till is employed.