Nitrogen Sources for Increasing Furrow Irrigated Hard White Wheat Protein.

Field studies on a Greenleaf silt loam were conducted at the Parma R & E Center during the 2007, 2008, and 2009 seasons to evaluate enhanced nitrogen fertilizers for improving protein of furrow irrigated hard white spring wheat (var “Otis”).  Enhanced preplant dry N (ESN, SuperU), jointing or boot stage foliar N (NFusion, Nitamin 30L) or boot stage topdressed dry N (Agrotain treated urea) were compared to conventional topdressed dry urea or foliar urea-ammonium nitrate at variable N rates, generally 33.6 and 67.2 kg N ha^-1.  Preplant basal N as urea (112 kg N ha^-1) was applied uniformly to all plots.  The N applied in addition to the basal N affected yield in only one of three years, had little or no effect on test weight or plant height, and seldom increased protein or grain N content, except for boot stage topdressed urea at the 67.2 kg N ha^-1 rate.  Preplant enhanced dry N fertilizers may be more convenient and were occasionally as effective, but neither these or foliar enhanced N fertilizers for this furrow irrigated system were as consistently effective as conventional topdressed dry urea N for increasing protein (0.5 to 0.7%) at the 67.2 kg N ha^-1 rate.  Topdressed dry urea at moderate rates was at least as effective in this calcareous soil as other N sources, despite wetted soils underneath the urea prill from furrow irrigation, a condition that could promote volatile NH₃ losses.