Over the past decade The Department of Agriculture, Trade and Consumer Protection (DATCP) has conducted several groundwater sampling programs that have contributed to the understanding of nitrate occurrence in Wisconsin groundwater. These studies have sampled both private drinking water wells and monitoring wells installed near
agricultural fields. Early studies focused on susceptible areas (coarse-textured soils, shallow depth to groundwater) and showed that nitrate contamination was a problem in these areas. Two recent monitoring-well studies have expanded our knowledge of nitrate behavior in areas with medium-textured soils such as silt loams. The purpose of this paper is to summarize the results of three DATCP monitoring well studies and make some conclusions about in nitrate occurrence in Wisconsin groundwater.