Drip irrigation is a water-saving and fertilizer-saving application technology used in recent years, with which the frequency of drip irrigation nitrogen application has not yet been determined. In order to investigate the effects of different drip irrigation nitrogen application frequencies on the processing quality of medium-gluten wheat (Jimai22) and strong-gluten wheat (Jimai20 and Shiluan02-1), a two-year field experiment was carried out. Two frequencies of water and N application were set under the same conditions of total N application (210 kg·ha⁻¹) and total irrigation (120 mm): DIF4, consisting of four equal applications of water and N (each of 30 kg·ha⁻¹ of N application and 30 mm of irrigation) and DIF2, consisting of two equal applications of water and N (each of 60 kg·ha⁻¹ of N application and 60 mm of irrigation). The results showed that IF4 significantly increased protein content by 2–8.6%, wet gluten content by 4.5–22.1%, and hardness value (p > 0.05), and PC2 was considered as a protein factor; the sedimentation value was highly significantly correlated with most of the parameters of the flour stretch (p < 0.01). DIF4 improved the stretching quality, and the flour quality of Jima22 was decreased, the flour quality of strong-gluten wheats Jimai20 and Shiluan02-1 was improved, and PC1 was considered to be the dough factor. In conclusion, although the frequency of nitrogen application by drip irrigation increased the protein factor and improved the tensile quality, the flour quality was not necessarily enhanced.

The North China Plain is one of the major wheat cultivation regions. As a cornerstone of global food security, wheat makes the enhancement of its yield critically important. Sulfur critically regulates photosynthesis, antioxidant defense, and grain filling dynamics. To elucidate the physiological mechanisms of S in wheat grain filling and guide field practices, a two-year field experiment (2022–2023 and 2023–2024) was conducted in the North China Plain using two dominant cultivars, Jimai 20 (JM20) and Yannong 999 (YN999). Four sulfur (ammonium sulfate) gradients (S1: 15 kg ha⁻¹; S2: 30 kg ha⁻¹; S3: 45 kg ha⁻¹; S4: 60 kg ha⁻¹) and a control (S0) were applied at the jointing stage via a drip fertigation system. The key findings reveal that optimal S application (YN999: 45 kg ha⁻¹; JM20: 30–45 kg ha⁻¹) enhanced post-anthesis photosynthetic capacity by increasing flag leaf SPAD values and superoxide dismutase (SOD) activity while reducing malondialdehyde (MDA) accumulation, thereby delaying leaf senescence. These improvements translated into optimized grain filling parameters: YN999 and JM20 exhibited 2.27–5.62% and 13.20–13.86% increases in mean grain filling rate, 3.92–4.73% and 2.11–4.36% extensions in grain filling duration, and 7.62–7.83% and 9.55–10.23% boosts in thousand grain weight, respectively. Consequently, yield increased by 0.58–1.54 t ha⁻¹ for YN999 and 1.36–1.49 t ha⁻¹ for JM20. Under drip fertigation conditions in the North China Plain, sulfur application at 30–45 kg ha⁻¹ effectively enhances wheat yield. These findings provide fertilization guidance for the development of precision agriculture and can help alleviate the local soil sulfur deficiency trend.