Effects of cultivars and nitrogen management on wheat grain yield and protein

Low grain protein in hard red winter (HRW) wheat (Triticum aestivum L.) is a serious challenge for rainfed wheat growers, particularly in years with elevated grain yield. Proper nitrogen (N) management with adequate N rate and application timing is critical for optimizing grain yield and protein content. This 2-yr experiment evaluated the effects of different N rates and application timings (fall, spring, and split) on grain yield and protein of two HRW wheat cultivars. Field studies were conducted at four different sites across Nebraska under rainfed conditions in 2018/2019 (Year 1) and 2019/2020 (Year 2). A split-plot randomized complete block design with wheat cultivars as the whole plots and factorial combinations of six N rates and three application timings as the subplots was used in four replications. Grain yield was associated positively and grain protein negatively with the water supply to demand ratio (WS/WD) in the season. Freeman cultivar yielded better in a year with higher WS/WD and a newly developed cultivar, Ruth, yielded better in a lower WS/WD year. Nitrogen fertilization significantly increased grain yield in the site-years with moderately higher WS/WD. There was an increase in grain protein with increasing N rates at all site-years. Spring and split-applied N resulted in better grain yield than fall application in the site-year when there was a risk of N loss. This experiment suggested that an effective N management strategy for winter wheat should account for and be adaptable to weather variability to optimize grain yield and protein content.