Nitrogen Application Rate Effects on Corn Yield and Nitrate-Nitrogen Concentration and Loss in Subsurface Drainage

TL;DRAbstract

Excess precipitation in Iowa and many other agricultural production areas is removedartificially via subsurface drainage systems that intercept and usually divert it to surface waters.Nitrogen (N), either applied as fertilizer or manure or derived from soil organic matter, can becarried as nitrate (NO3) with the excess water in quantities that can cause deleterious effectsdownstream. Over a 16-year period, three N-rate treatment phases with five seasons (six forPhase II) each were imposed on conventionally tilled, subsurface drained, continuous-flowmonitoredplots. The field study was initiated in the spring of 1989 in Pocahontas County, Iowaon 0.05-ha plots that are predominantly Nicollet, Webster, and Canisteo clay loams with 3-5%organic matter. The objective was to determine the influence of N fertilizer rates on flowweightedNO3-N concentration and loss along with yield in a corn-soybean rotation, over a widerange of weather conditions. Phase I N rates ranged from 0-168 kg N ha-1 in

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