Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 28, 2004
Publication Date: N/A
Technical Abstract: The primary purpose of conservation tillage is to reduce soil loss. Unfortunately, the herbicides normally used are often detected in surface runoff at high levels. Therefore, we used 7 small (0.45-0.79 ha) watersheds to investigate whether a reduced-input practice for corn and soybean production with light disking, cultivation, and half-rate herbicide applications could reduce herbicide loss compared to chisel and no-till. Runoff volumes and concentrations of atrazine, alachlor, linuron, and metribuzin were monitored for 9 years (1993-2001). Herbicide losses varied considerably among watersheds and years as a result of variation in rainfall. As a percent of application, average annual losses were highest for all herbicides for no-till and were similar for chisel and reduced-input. Atrazine was the most frequently detected herbicide and yearly flow-weighted concentrations frequently exceeded the drinking water standard of 3 ug/L. Averaged for the 9 years, yearly flow-weighted atrazine concentrations were 23.7, 9.6, and 8.3 ug/L for no-till, chisel, and reduced-input, respectively. Similarly, flow-weighted concentrations of alachlor frequently exceeded the drinking water standard of 2 ug/L for all treatments. Thus, while banding and half-rate applications as part of a reduced-input practice reduced herbicide loss in runoff, concentrations of some herbicides may still be a concern.