Relationship of nitrogen management to winter wheat yield and grain protein in South Dakota

The effects of nitrogen (N) management systems on Rose and Arapahoe hard red winter wheat (Triticum aestivum L. Emend. Thell.) were measured. Nitrogen fertilizer rates of 0, 55, 110, and 165 kg N ha(-1) were surface broadcast as a full N rate application at preplant or were split-applied as two half N rates applied in the fall and spring. Supplemental N was also applied as a foliar spray treatment after anthesis at either 0 kg N ha(-1) or 33 kg N ha(-1) as a diluted urea-ammonium nitrate solution. The grain yield of Arapahoe was generally higher than Rose across treatments, but protein was slightly lower. Splitting the N application lowered yield somewhat in both varieties compared to the entire N rate applied at preplant, but grain protein increased by nearly 0.8% with the split application over the preplant application. Grain protein also increased up to 1.6% with a late season foliar N application despite some leaf damage compared to no foliar N. Grain yield was correlated to many agronomic parameters measured throughout the growing season, but grain protein was correlated only to shoot N concentration in samples harvested at the soft dough stage (Feekes stage 11.2).