Nitrogen Effects on Soft Red Winter Wheat Yield, Agronomic Characteristics, and Quality

Research conducted in the USA in recent years has verified that grain yields of soft red winter (SRW) wheat (Triticum aestivum L.) can be increased by intensification of management procedures, including higher N fertilization. Relatively little information has been reported on how N, cultivar, and their interaction influence end use qualities of SRW wheat. Field studies were conducted in 1983 and 1984 on a Greenville sandy clay loam (clayey, kaolinitic, thermic Rhodic Paleudults) to determine the influence of applied N on above ground biomass, grain yield, kernel weight, and grain protein of five SRW wheat cultivars. Nitrogen effects on tiller density, kernels per head, and SRW wheat milling and baking quality were determined in 1983 but not 1984. Nitrogen treatments were 0, 33.6, 67.2, 100.8, and 134.4 kg N ha⁻¹, applied as two equal topdressings between the tellering and early jointing growth stages. Nitrogen and cultivar affected all response parameters. Nitrogen × cultivar interactions were important only for grain protein content. Biomass and grain yield were maximized with 106 and 94 kg N ha⁻¹, respectively. As N rate increased, grain protein, tiller density, and kernels per head increased, while harvest index and kernel weight decreased. Nitrogen rates in excess of 67 kg N ʰᵃ⁻¹ caused luxurious N consumption and contributed to undesirable grain protein increases in both years, and reduced SRW wheat milling and baking quality by increasing flour protein and endosperm hardness in 1983. ‘Omega 78’ was more adapted to higher N regimes than the other cultivars evaluated, producing the highest grain yield and lowest average grain protein content, having superior overall milling and baking qualities, and having the most favorable grain protein response pattern to increased N rates. Contribution from the Dep. of Agronomy, Univ. of Georgia College of Agric. Exp. Stn., Coastal Plain Exp. Stn. Supported by Hatch and state funds allocated to the Georgia Agric. Exp. Stn.