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

Abstract

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.

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

“…Improvement in grain protein content of winter wheat with split applied N was reported in previous studies (Dhillon et al, 2020;Garrido-Lestache et al, 2004;Lollato et al, 2021). Our result aligned with the finding of Graham and Stockton (2019) who observed no significant increase in grain protein content by split N application over the at-sowing N application.…”

“…Given the high variability in weather and grain yield response to applied N, split or spring application of N provides additional advantage allowing to make economy-based decision on whether to fertilize or terminate winter wheat as a cover crop in spring and plant other crops such as maize in spring. Improvement in grain protein content of winter wheat with split-applied N was reported in previous studies (Dhillon et al, 2020;Garrido-Lestache et al, 2004;Lollato et al, 2021). Our result aligned with the finding of Graham and Stockton (2019) who observed no significant increase in grain protein content by split N application over the at-sowing N application.…”

“…Higher plant biomass from increased N uptake during early growth stages and low remobilization of N to the grains might also be a potential reason for inverse grain yield–protein relation (Gaju et al., 2014). However, the positive relationship between grain yield and protein observed at some site‐years suggests that the negative relationship is not universal (Lollato et al., 2021; Torrion et al., 2019). Grain protein content is sometimes identified as an indicator of N sufficiency (Goos et al., 1982).…”

“…Environmental index (EI) values were calculated by averaging variables across cultivars as described in Lollato et al. (2021) to explain the cultivar × environment interaction effect on grain yield and grain protein content using the concept of adaptability and stability (Eberhart & Russell, 1966).…”

“…However, the positive relationship between grain yield and protein observed at some siteyears suggests that the negative relationship is not universal (Lollato et al, 2021;Torrion et al, 2019). Grain protein content is sometimes identified as an indicator of N sufficiency (Goos et al, 1982).…”