Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/9/1996
Publication Date: N/A
Technical Abstract: The principal focus of the Management Systems Evaluation Area (MSEA) project initiated in 1990 was to develop and evaluate alternative farming systems to improve ground water quality. Projects in IA and MO also conducted research to assess the influence of prevailing and alternative farming systems on surface water quality at the field, subbasin, and watershed scales. The 5,130-ha Walnut Creek watershed in central IA is dominated by corn-soybean rotational cropping. Cropping within the 7,250-h dwater Creek watershed in north-central MO is more diverse. Streamflow from each watershed is comprised of two components, surface runoff and baseflow. Baseflow represents nearly continuous recharge to the stream from ground water. The outlet of each watershed is instrumented to measure streamflow and automatically collect samples at streamflows higher than baseflow. Baseflow samples are collected at weekly intervals. All samples have been analyzed for atrazine, alachlor, metribuzin, and metolachlor. Mean annual streamflow from the Walnut Creek and Goodwater Creek watersheds for the 1992 through 1995 period was 351 and 1,112 mm/ha, respectively. The highest herbicide concentrations from both watersheds occurred at higher streamflows associated with surface runoff events, particularly during the 45- to 60-day period following spring herbicide application. Atrazine and metolachlor concentrations were much higher than those for alachlor and metribuzin. Mass losses of herbicides in streamflow from both watersheds were very low relative to the amounts applied by producers. Long-term monitoring of these watersheds will provide an excellent data base of how field and watershed management practices influence the quality and quantity of streamflow discharge.