Effects of long-term tillage practices on grain-filling and yield formation in rain-fed wheat

Seasonal drought remains a major constraint to yield improvement in the rain-fed wheat region of Huang-Huai-Hai. This study explores the physiological and ecological mechanisms by which tillage practices enhance drought resistance and conserve soil moisture to stabilize wheat production, aiming to provide a theoretical foundation for optimizing drought-resilient regional farming systems. Based on a 14-year long-term field experiment using the wheat cultivar Jimai 22, three tillage systems were compared: perennial deep tillage with straw incorporation (DT), perennial rotary tillage (RT), and perennial minimum/no tillage (NT). Field measurements during the 2018-2020 growing seasons included assessments of soil water consumption, assimilate translocation and assimilation dynamics, grain filling characteristics, and yield components. While total soil water consumption within the 0-60 cm soil layer did not differ significantly among DT, RT, and NT treatments, DT significantly reduced water consumption during the sowing-to-jointing period by 19.64%-29.67% (2018-2019) and 5.12%-10.97% (2019-2020) compared with RT and NT, and conversely increased water consumption during the jointing-to-maturity period by 17.16%-45.38% and 7.20%-12.74% in the respective years. No significant differences in post-anthesis dry matter assimilation were observed between DT and RT, but both were significantly higher than NT. Additionally, DT enhanced the contribution of post-anthesis assimilates to grain by 0.50-20.07 percentage points (2018-2019) and 4.32-16.29 percentage points (2019-2020) compared to RT and NT, respectively. Logistic equation fitting indicated that DT achieved higher maximum and mean grain filling rates and longer grain filling durations than both RT and NT. Correlation analysis further revealed that increased soil water consumption during the anthesis-to-maturity period was the primary driver for enhanced post-anthesis assimilate accumulation, improved grain filling parameters, and increased grain yield. Ultimately, DT resulted in a 15.67% yield increase over NT in 2018-2019, and yield improvements of 5.34% and 8.61% over NT and RT, respectively, in 2019-2020. Therefore, compared to rotary tillage and minimum/no-till systems, deep tillage with straw incorporation emerges as the most effective strategy for stabilizing and enhancing rain-fed wheat yields. This is achieved through a water management advantage characterized by early-stage water conservation and late-stage water supply compensation, which collectively enhance post-anthesis assimilate accumulation and translocation, significantly increase grain filling rates, prolong the effective grain filling period, and synergistically optimize yield components including spike number, kernels per spike, and thousand-kernel weight.