Yield‐Protein Relationships in Wheat Grain, as Affected by Nitrogen and Water1

Abstract Highly significant inverse yield‐protein relationships in wheat grain were found at each level of applied N in an irrigation‐N rate experiment on hard red winter wheat over a 3‐year period at North Platte, Nebraska. The chief effect of applied N with adequate water was to increase yields, while the chief or entire effect with severe water deficits was to increase protein content. In intermediate situations, N increased both yield and protein content. In dryland experiments in 1966 and 1967 showing significant grain yield response to applied N, protein content also increased. Where little or no yield response occurred, N mainly increased protein content. Content of NO 3 −N in the soil to a depth of 180 cm was also important in yield‐protein relationships. Average protein contents of about 20 hard red winter wheat varieties at different locations in Nebraska in 1966 and 1967 were also negatively related to grain yields. Protein contents varied more widely among locations than among varieties at each location.