Agrichemical Loading to Groundwater Under Irrigated Vegetables in the Central Sand Plain

Executive Summary: Agrichemicals are widespread groundwater pollutants in many agricultural regions of the US, including the Wisconsin central sand plain. In the Agricultural Statistics District that includes much of the central sands, 22% of exploitable groundwater exceeds the federal maximum contaminant level (MCL) for NO3-N (10 mg L”!) and > 23% contains at least one herbicide (LeMasters and Baldock, 1995). Present strategies to alleviate agricultural impacts on groundwater in the central sands, primarily implementation of agricultural best-management practices (BMPs), have not substantially improved groundwater quality. New strategies are needed, but their development requires more information about the quality of groundwater that results from the prevailing agricultural systems, and about the impacts, transport, and fate of agrichemicals in groundwater basins.

This study was undertaken to assess the impacts of irrigated vegetable agriculture on groundwater in Wisconsin’s central sands. The objectives were to measure groundwater quality and solute loading under an irrigated vegetable field, and investigate the transport of agrichemicals beyond vegetable fields. This study is a partial continuation of an earlier study Oe (Kraft et al., 1995) in the Port Edwards Groundwater Priority Watershed. The current study added two more years of data (3 March 1994 to 30 March 1996) from one irrigated vegetable field and from monitoring wells in the northern portion of the Priority Watershed.