Subsurface P loss is of greatest concern in areas with P-rich flat, clayey soils and P-rich tile-drained soils (Beauchemin et al., 1998). Eastern Wisconsin farmland fits the criteria for high subsurface P emitting soils. Soil tests conducted between 1995 and 1999 indicated that the average soil P levels in eastern Wisconsin counties were in excess of the recommended levels for most crops (Laboski et al, 2006). Additionally, considerable portions of eastern Wisconsin’s cultivated acres are tile-drained. The highest concentration of tile drainage is along the shore of Lake Michigan. The 1992 United States Census of Agriculture estimates the portion of cultivated acres that are tile drained to range from 20 to 60% among all of Wisconsin’s far-eastern counties (Kewaunee, Manitowoc, Sheboygan, Ozaukee, Milwaukee, Racine, and Kenosha).
Soil Science Extension
University of Wisconsin Madison