Objective Post-anthesis drought and nutrient depletion constitute significant yield-limiting factors in dryland wheat systems. Optimizing soil moisture conservation and fertilization strategies is therefore imperative for enhancing the synergistic efficiency of water and nitrogen utilization and improving grain yield.

Methods A field experiment was conducted from 2022 to 2024 at the dryland wheat experimental base in Wenxi, Shanxi Province, China. Treatments consisted of two tillage practices (no-tillage and deep plowing) combined with three nitrogen fertilizer application rates (135, 180, and 225 kg/hm²) under different precipitation year conditions. Post-anthesis soil moisture consumption, photosynthetic characteristics, nitrogen translocation and utilization, and yield of dryland wheat were systematically evaluated.

Results Compared with no-tillage, deep plowing during the fallow period significantly increased soil water storage in the 0−200 cm layer at anthesis, with increases of 4.43−8.39 mm in wet years and 10.74−28.63 mm in dry years, mainly attributable to enhanced water storage in the deep layer (100−200 cm) . Compared to no tillage, deep plowing promoted post-anthesis soil water consumption toward deeper layers, with the main depletion depth moving downward by approximately 20 cm in dry years. In wet years, deep plowing combined with 225 kg/hm² nitrogen fertilizer compared to other nitrogen fertilizer treatments,increased post-anthesis water consumption by 11.35 mm, whereas in dry years, deep plowing combined with 135 kg/hm² nitrogen fertilizer compared to other nitrogen fertilizer treatments increased water consumption by 36.33−43.48 mm. Compared to no tillage, deep plowing during the fallow period significantly increased the peak activities of Rubisco and RCA in flag leaves at 25 days after anthesis and extended their functional period by 5 days. Correspondingly the post-anthesis net photosynthetic rate increased by 18.3% In wet years under 225 kg/hm² nitrogen fertilizer and by15.6% in dry years under 135 kg/hm² nitrogen fertilizer,. Moreover, Compared to no tillage, deep plowing during the fallow period increased pre-anthesis nitrogen translocation and, in synergy with increased post-anthesis deep-layer water consumption, promoted nitrogen accumulation. In dry years, the 135 kg/hm² nitrogen fertilizer treatment resulted in post-anthesis nitrogen accumulation and its contribution rate to grain that were 72.65%−89.03% and 24.91%−31.32% higher than those of other treatments, respectively. Yield and water-nitrogen use efficiency analyses showed that deep plowing during the fallow period significantly increased spike number, grains per spike, and 1000-grain weight, thereby resulting yield increases of 6.98%−15.14% in wet years and 6.89%−20.00% in water-deficit years. In wet years, the 225 kg/hm² nitrogen fertilizer treatment achieved the highest yield of 8014.69 kg/hm² by increasing spike number by 3.16%−12.25% and 1000-grain weight by 1.29%−5.17%, but reduced water and nitrogen use efficiency. In dry years, the 180 kg/hm² nitrogen fertilizer treatment obtained the highest yield of 6168.78 kg/hm² and improved water and nitrogen use efficiency, with no significant differences in yield and water use efficiency compared with the 135 kg/hm² treatment. Correlation analysis revealed significant positive relationship among post-anthesis Rubisco activity, stem nitrogen translocation, and deep-layer water consumption, which constituted the physiological basis for yield improvement.

Conclusion Deep plowing during the fallow period combined with an appropriate nitrogen application rates (180−225 kg/hm² in wet years; 135−180 kg/hm² in dry years) facilitates the storage of precipitation insoil layers below 100 cm and its subsequent utilization after anthesis. This management strategy strengthens the reuse of water and nitrogen after anthesis, improve photosynthetic performance and yield formation, and enhance the climate resilience of rain-fed agricultural ecosystems, thereby providing a theoretical basis for high-yield and high-efficiency cultivation of dryland wheat.