Research focused on the effects of nitrogen (N) management on crop production and tile drainage water quality has been conducted in north-central Iowa near Gilmore City since 1989. The research site ag drainage well (ADW) includes 72 individually drained plots that are 50 feet wide and 125 feet long (Figures 1 and 2). Tile lines were installed at a depth of 3.5 feet spaced 25 feet apart. The center tile line from each plot is pump monitored continuously for drainage volume with a flow meter and a flow-proportional sample is passively collected for nitrate-nitrogen (nitrate-N) and dissolved phosphorus (P) analysis (Figure 3). Drainage flow is recorded and water samples are collected for analysis weekly. Soil types at ADW include Nicollet, Webster and Canisteo, all of which are clay loams. The 30-year average annual rainfall for ADW is 33.5 inches