Objectives Studies on grain protein content, nitrogen (N) use efficiency, and wheat yield under different basal and topdressing ratios of N fertilizer have laid the theoretical basis for improved N-use by wheat in the Heilonggang basin, Hebei Province.

Methods Two-year field experiment was conducted with two wheat cultivars (Jimai 22 and Gaoyou 2018). No nitrogen fertilizer (N₀) was designated as the control. Under the same rate of N application, four N treatments with a basal topdressing ratio of 3∶7 (N_3:7), 4∶6 (N_4:6), 5∶5 (N_5:5) and 6∶4 (N_6:4) were set. Nitrogen topdressing was carried out with irrigation at the jointing stage. We analyzed the dry matter and N accumulation during the wheat main growing period, grain total protein content and various protein components, nitrogen efficiency and grain yield in the two wheat cultivars.

Results Dry matter and N accumulated quantities in the two wheat cultivars increased at first and then decreased with increasing N basal topdressing ratio. As the growth period advanced, plant dry matter accumulation rate in the two wheat cultivars increased and then decreased. Similarly, the N accumulation rate showed an increase-decrease-increase trend. The stage from jointing to flagging was the main period for wheat dry matter and N accumulation. At maturity, the dry matter and N accumulation were higher in N_4:6 and N_5:5 than in other treatments in Gaoyou 2018 and Jimai 22. N_4:6 in Gaoyou 2018 had higher grain albumin, globulin and glutenin contents than other treatments, increasing total grain protein by 3.66%–10.76% and grain yield was 1.07–1.13 times of other treatments. Further, it increased the N partial productivity, N recovery rate, and agronomic efficiency. N_5:5 in Jimai 22 increased albumin by 2.55%–4.78%, globulin by 4.11%–16.92%, gliadin by 3.42%–10.39%, glutenin by 1.35%–10.32%, and total protein content by 2.95%–10.06%. The grain yield was 1.03–1.08 times of other N treatments, significantly increasing the N recovery rate. The N accumulation rate from flagging to maturation stage in Gaoyou 2018 was relatively higher than Jimai 22; grain protein components of Gaoyou 2018 were 1.17%–5.72% higher than Jimai 22. In contrast, the grain yield in Jimai 22 was 5.4%–15.21% higher than in Gaoyou 2018.

Conclusions The basal to dressing ratio of nitrogen fertilizer that meets the N accumulation characteristics of wheat is conducive to high wheat yield and quality. The N accumulation rate of medium gluten wheat cultivar decreased from flagging to maturation stage, and the basal topdressing ratio of N fertilizer was 5∶5. In contrast, the N accumulation rate of strong gluten wheat cultivar was high from flagging to maturation stage. The basal topdressing ratio of N fertilizer is increased to 4∶6, which potentially enhances high yield and grain protein content in wheat.