Effects of main cultivation practices on simultaneous improvement in grain yield and protein content of strong-gluten wheat: a Meta-analysis

The consumption of bread made from strong-gluten wheat is rapidly increasing in China, however, commercially available wheat grains of sufficient quality for bread-making remain scarce in the domestic market. A high grain protein content (GPC) is desirable in strong-gluten wheat, but a decrease in grain yield (GY) is usually observed when achieving the targeted GPC in production. Sowing date, nitrogen application rate, and plant density are effective cultivation practices for regulating GY and GPC in strong-gluten wheat. In this study, a meta-analysis was performed on the effects of these main cultivation practices on the GY and GPG of strong-gluten wheat in the Huang-Huai-Hai Region using existing literature data from 2003 to 2023. The control (CK) was selected from October 10 to October 25 for sowing date, from 270 to 300 kg·hm⁻² for nitrogen rate, and from 180×10⁴ to 240×10⁴ plants·hm⁻² for plant density, respectively. The meta-analysis showed that when the sowing date was delayed by 0–35 d, the GY of strong-gluten wheat was significantly reduced by 2.86% to 19.22%, and a sharp drop occurred from a delay of 21 to 28 d. Moreover, GPC significantly decreased by 4.08% with a 0–7 day delay in sowing, whereas a 21–28 day delay led to a significant increase of 10.54%. When the nitrogen rate was reduced by 0 to 30 kg·hm⁻², the GY was significantly increased by 4.67%; however, the GY was significantly decreased by 2.75% and 4.69%–36.84% when the nitrogen was reduced by 30–60 kg·hm⁻² and 90–300 kg·hm⁻², respectively. Meanwhile, a reduction in nitrogen application rate from 30 to 240 kg·hm⁻² resulted in an average decrease of 4.31% to 23.54% in GPC. When the plant density was increased by 0 to 90×10⁴ plants·hm⁻², the GY was significantly improved by 1.73%–3.59%; and an average increase of 2.01%–2.61% was observed in the GPC when the plant density was increased by 30×10⁴ to 90×10⁴ plants·hm⁻². Furthermore, the relationship between GY and GPC of strong-gluten wheat was analyzed under different cultivation practices mentioned above in this region. The qualified grain quality (GPC＞14.0%) while maintaining high yield (GY＞8 000 kg·hm⁻²) could be obtained with the sowing date from October 10 to October 21, the nitrogen rate from 230 to 286 kg·hm⁻², and the plant density from 247×10⁴ to 289×10⁴ plants·hm⁻². Correspondingly, the dry matter accumulation of strong-gluten wheat ranged between 14.7 and 17.0 t·hm⁻² at anthesis as well as 20.4 and 26.6 t·hm⁻² at maturity, while the nitrogen content of single stem, stems, leaf, and ear at anthesis was maintained within 16.0, 9.0, 34.0 and 14.5 mg·g⁻¹. These findings would provide novel approaches for the simultaneous improvement in the grain yield and quality of strong-gluten wheat for bread making in the Huang-Huai-Hai Region.