Genotype‐specific nitrogen uptake dynamics and fertilizer management explain contrasting wheat protein concentration

Increasing yield and grain protein concentration (GPC) in wheat (Triticum aestivum L.) without excessive nitrogen (N) rates requires increasing N use efficiency (NUE, yield per available N). We assessed the effects of N rate and timing on yield, GPC, and N nutritional indices of two winter wheat genotypes with similar yield but contrasting GPC. Factorial field experiments evaluated the wheat genotypes ‘LCS Chrome’ (high GPC) and ‘WB–Grainfield’ (low GPC), three N rates, and four N timings (‘Fall’, 100% of N rate applied at Zadoks GS20; ‘Spring’, 100% at GS25; ‘Split’, 40% Fall plus 60% Spring; and ‘Anthesis’, 40% fall, 50% spring, and 10% at GS61) in six Kansas environments. Yield ranged from 2,853 to 8,023 kg ha‐1 and GPC from 88 to 152 g kg‐1. Fall and spring N timing had the lowest and greatest yield difference from the zero‐N control and showed linear, linear‐plateau or no responses to N rate. ‘LCS Chrome’ had 5 to 19 g kg‐1 greater GPC than ‘WB–Grainfield’, which was associated with greater post‐anthesis N uptake (24 vs 15% of maturity‐N uptake), a greater spike N gain between anthesis and maturity (7.4 vs 6.5 g m‐2), and greater N recovery efficiency (0.34 vs 0.28 kg kg‐1). Greater N rates and Anthesis or Spring N timings increased GPC. The NUE (range: 20–311 kg kg‐1) was inversely related to N availability, and Fall N timing had the lowest NUE. Our results highlighted physiological reasons for genotype‐specific GPC performance and suggested agronomic opportunities to simultaneously improve wheat yield and GPC. Core Ideas We explored opportunities to improve winter wheat yield and protein simultaneously Genotypic differences in protein accumulation related to post anthesis N uptake Split and spring N timing outperformed fall N timing in yield, protein, and N efficiency indices N use efficiency related inversely with N availability and was lowest in the fall N timing The N management and genotypes evaluated loosened the negative yield‐protein relationship