Submitted to: ASA-CSSA-SSSA Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 23, 2003
Publication Date: November 2, 2003
Citation: Graff, C.D., Koskinen, W.C., Rice, C., Sadeghi, A.M., Bialek-Kalinski, K.M. 2003. Spatial and temporal variability of agricultural chemicals at field and watershed scales [CD-ROM]. In: ASA-CSSA-SSSA Proceedings. ASA-CSSA-SSSA International Annual Meetings, November 2-6, 2003, Denver, CO. p. 93. Technical Abstract: Soil and landscape characteristics that influence herbicide behavior vary spatially at the scales of most agricultural fields. Ultimately this could give rise to spatial variability in soil/sorption, degradation and transport processes affecting herbicide dissipation. Variability in transport within a field may affect the amount of herbicide leaving a system via subsurface flow to a greater extent than assuming uniform dissipation. An initial study to determine the degree to which herbicide dissipation is spatially variable within a field was conducted on a 6 ha watershed in Dakota County, MN. Geostatistical analysis indicated spatial dependency of herbicide dissipation, up to 40% of which could be explained by some combination of soil properties and/or terrain attributes. A similar study at Beltsville Agricultural Research Center investigating the dissipation of metolachlor and atrazine within a small watershed is underway. Preliminary results indicate variability in pre-application concentrations of two metolachlor metabolites (ESA and OXA) within sampling wells located down gradient at the edge of the field. Herbicide concentrations in wells within the field and adjacent riparian buffer zone link up with the edge of field wells, indicating a relationship between field dissipation processes and off-site transport. Post-application variability will also be evaluated.