Field research has been conducted on poorly drained soils since the 1970s to determine the effect of numerous nitrogen (N) and drainage management practices on nitrate losses from agricultural production systems. This research has clearly shown that nitrate concentrations and losses in drainage water are primarily affected by the amount, temporal distribution, and intensity of precipitation and cropping system, but N management (rate and time of application, source, and nitrification inhibitors) and drainage management (controlled drainage, tile spacing, and depth) also play a significant role. Rate of N applied, especially if greater than needed, has a larger effect on N loss than does time of application, source, or inhibitor. Interactions among these management practices coupled with hydrologic factors often adds complexity to understanding these N management relationships. Controlled drainage can reduce nitrate losses substantially, but needs to be synchronized with hydrologic factors and field operations to be most effective. Nitrate losses can also be reduced by installing tile more shallow (<1.0 m vs. 1.2m) and at a wider spacing (25m vs. 15m), due to less water being discharged.