Yields and Protein Content of Wheat Grain as Affected by Cultivar, N, and Environmental Growth Factors 1

Grain protein is important in human and animal nutrition and in relation to various culinary uses of flour. Various wheat ( Triticum aestivum L.) cultivars are reported to vary widely in grain yield and protein concentrations. To study yield‐protein relationships, three soft red winter (Atlas 66, Knox 62, and Blue Boy) and three hard red winter (Norin 16, Tascosa, and Omaha) wheat cultivars were grown in a pot experiment at Muscle Shoals, Alabama. Response to 0, 100, 200, 400, 800, and 1,200 mg of N/pot (3 kg of Mountview silt loam) together with adequate, uniform rates of other nutrients was determined. All cultivars increased similarly in grain and straw yields, crude protein concentrations, and crude protein / pot with amount of applied N. The ranking for grain yields was: Tascosa > Blue Boy = Knox 62 > Omaha > Norin 16 > Atlas. The ranking for crude protein concentrations was in the reverse order. These trends indicate pronounced genetic differences among cultivars. At each rate of applied N, protein concentrations were also inversely related to grain and straw yields. Early uptake of N at forage and boot stages of growth was usually highly correlated with uptake in grain + straw at maturity. Nitrogen and moisture supply, light, temperature, and other growth factors greatly affect yield‐protein relationships among cultivars. Differences among cultivars tended to be greatest under optimum growth conditions.