ARS | Publication request: Combining long-term herbicide monitoring with identification of vulnerable areas in restrictive layer watersheds

Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2012
Publication Date: August 28, 2011
Citation: Lerch, R.N., Baffaut, C., Sadler, E.J., Kitchen, N.R., Sudduth, K.A. 2011. Combining long-term herbicide monitoring with identification of vulnerable areas in restrictive layer watersheds [abstract]. American Chemical Society National Meeting, August 28-September 1, 2011, Denver, Colorado. 12801.

Technical Abstract: Long-term monitoring of herbicide concentrations and loads has been conducted at Goodwater Creek Experimental Watershed (GCEW) located in northeastern Missouri, a watershed dominated by soils with a naturally formed smectitic claypan. From 1992 to 2006, trends in herbicide concentration and load were only observed for compounds in which major changes in usage had occurred. For example, atrazine use increased 25 percent from 1992 to 2006 and no trends were observed in load or concentration. Atrazine loads did, however, vary greatly over the 15 year period analyzed, ranging from 1 to 14 percent of applied. A newly developed cumulative vulnerabiliy index explained 63 percent of the variation in annual atrazine loads for GCEW, and it explained 85 percent of the variation in unit area loads when extended to the and when extended to the entire Salt River basin. Efforts developed to identify vulnerable areas within these watersheds have shown that the top soil depth over the claypan and slope are critical risk factors for transport by surface runoff.