Nitrate-nitrogen (N03-N) loss to surface water bodies and groundwater resources from production agricultural systems is of local and regional concern throughout the Midwestern United States. This is especially of concern in areas where artificial subsurface drainage systems are utilized. Water table management through the use of artificial subsurface drainage systems is important in humid areas with poorly or somewhat poorly drained soils to maximize agricultural productivity. Excess precipitation in Iowa and many other Midwestern U.S. agricultural production states is removed artificially via subsurface drainage systems that intercept and usually divert it to surface waters. Subsurface drainage systems have been installed to allow timely seedbed preparation, planting and harvesting and to protect crops from extended periods of flooded soil conditions. While these drainage systems are essential in maximizing crop production, the tradeoff of improved subsurface drainage is a significant increase in the losses of N03-N (Gilliam et al., 1999). Nitrogen, either applied as fertilizer, or manure or derived from soil organic matter, can be carried as nitrate with the excess water in quantities that can cause deleterious effects downstream. The movement of nitrogen from agricultural fields via drainage waters is a major factor in nonpoint source pollution of surface waters and ultimately the Gulf of Mexico where it has been implicated as a contributor to the Hypoxic Zone (Mitsch et al., 2001; Rabalais et al., 1996).