Environmental and Agronomic Impacts of Manure and Fertilizer Nitrogen Management in the Wisconsin Central Sands

The Central Sands of Wisconsin is a 64,000 km2 region with relatively flat topography encompassing six counties. It has a mantle of coarse-grained Pleistocene glaciofluvial and lacustrine sediment, which overlies crystalline rock and sometimes sandstone. This sandy plain represents the lake bottom of what was once Glacial Lake Wisconsin. The soils are extremely sandy and very well drained, with topsoils averaging 93% sand and 1 % organic matter and subsoils averaging 98% sand and 0.1 % organic matter (Kraft et al., 1999).

Limiting groundwater contamination from nitrogen fertilizer application has been a struggle in the Central Sands. Bundy and Andraski (2005) found an average nitrate concentration of 18 mg L-1 in groundwater at Hancock Agricultural Research Stations, which exceeds the Environmental Protection Agency’s maximum contamination level (MCL) of 10 mg N03-N L-1. Saffingna and Keeney (1977) found that shallow wells located in grassed areas contained minimal amounts of nitrate compared to those located in agricultural areas. Stites and Kraft (2000) reported average groundwater nitrate concentrations of21 mg L ·1 under agricultural fields, while up-gradient nonagricultural areas were I mg L-1. Stites and Kraft (2000) concluded that no more than half of the Central Sands .could be used for irrigated agricultural purposes if average nitrate levels are to be less than the MCL. Other studies have also linked high groundwater nitrate concentrations to agricultural inputs (Kraft and Stites, 2003; Saad, 2008).

Historically, very few cattle were raised in the Central Sands of Wisconsin (Gutenberg, 2009). Today, large dairy confined feeding operations are located within the Central Sands, with more proposing to move into the area. With these large dairy farms comes an associated increase in manure production. As manure production increases, more manure will be applied to agricultural fields as a plant nutrient source in-lieu of and in conjunction with conventional synthetic fertilizers. In an area where groundwater contamination has been directly linked to agricultural activity, an increase in manure application is creating concern within the community. Therefore, determining the nitrogen availability from dairy manure and minimizing the potential for groundwater contamination is critical for ensuring continued agricultural productivity and promoting environmental integrity.

Final report was submitted as a thesis:

Schulz, L. A. (2014). Environmental and agronomic impacts of manure and fertilizer nitrogen management in the Wisconsin Central Sands. [Unpublished master’s thesis]. University of Wisconsin-Madison.

Author has given permission to provide full text of thesis.