Improved soil environment and physiological time-compensation drive maize yield catch-up and lower water requirement thresholds under continuous straw mulching

Although plastic film mulching generally outperforms straw mulching in reducing irrigation requirements and enhancing short-term crop yield, the time-cumulative catch-up advantage of continuous straw mulching in terms of soil improvement and crop physiology is largely underestimated. In particular, the synergistic soil-physiological mechanisms driving this yield catch-up effect relative to plastic film mulching remain poorly understood. A three-year (2023–2025) field experiment was conducted in a semi-arid region of China to investigate the regulatory mechanisms of maize growth and senescence processes on grain yield under plastic film mulching (PM) and straw mulching (SM) across diverse irrigation levels (0%, 75%, 100%, 125%, and 150% of crop evapotranspiration, ET c ). The results demonstrated that grain yield and water productivity exhibited significant non-linear responses to the irrigation gradient. The optimal irrigation amount under PM remained stable at approximately 75%ET c . Straw mulching over the three years exhibited a pronounced "catch-up effect", with the water requirement threshold for optimal yield in SM decreasing from 126.88%ET c in 2023–108.91%ET c in 2025. Consequently, the yield gap between SM and PM narrowed from 21.6% in 2023–9.2% in 2025. Moreover, continuous SM progressively optimized the subterranean environment, significantly enhancing soil organic carbon and total soil porosity over the three consecutive years compared to PM. Physiological mechanism analysis indicated that compared to PM, continuous SM exhibited more stable coordination between photosynthetic enzymes and net photosynthetic rate. Crucially, when coupled with 100%ET c , SM established a stronger antioxidant defense system than PM. This cumulative advantage progressively delayed leaf senescence; by the third year (2025), the senescence onset time under SM caught up to and exceeded PM by up to 1.5 d. These pathways collectively widened the duration of high-efficiency photosynthesis, effectively compensating for the lower growth rates of SM during early developmental stages. This "time-compensation mechanism" based on the extension of high-efficiency photosynthesis duration elucidates the physiological foundation for the steady yield catch-up of straw mulching, providing robust theoretical support for the sustainable management of dryland agriculture in semi-arid regions.