In the water-scarce North China Plain (NCP), choosing between straw mulching (SM) for surface conservation and straw incorporation (SI) for soil amelioration is a critical agricultural dilemma. However, their effects on soil water dynamics and crop productivity under different irrigation levels remain unclear. We conducted a two-year field experiment comparing SI and SM under three irrigation levels in winter wheat: no irrigation (I0), 60 mm irrigation at jointing (I60), and 60 mm irrigation at both jointing and heading (I60 + 60). Soil water dynamics were monitored, field-scale evapotranspiration (ET) was estimated using a water-balance approach, and aboveground dry matter, yield components, and water use efficiency (WUE) were measured. SM maintained higher topsoil water content early in the season, whereas SI generally showed greater changes in soil water storage (DSWS) and higher mean daily ET. Despite weaker early-stage surface water conservation, SI increased aboveground dry matter and grain yield by 5.2%–5.6%, resulting in 3.4%–4.0% higher WUE, with the advantage reaching 4.8%–4.9% under I60. This advantage was associated with improved early sink establishment (higher spike numbers) and superior ET conversion efficiency, requiring 18.8% less ET per unit dry matter increment. Under I60 + 60, the relative advantage of SI narrowed, indicating diminishing marginal yield response to additional ET. A conceptual model was developed to synthesize these straw return-irrigation interactions. We identified SI-I60 + 60 (highest yield) and SI-I60 (highest WUE) as optimal coupling modes, and recommend SI-I60 as the optimal management practice for this region, offering a practical strategy for winter wheat production under water-limited conditions.

Subsoiling is widely used to improve soil productivity in the North China Plain (NCP). However, its effects on pore network-based hydraulic properties and their relationship with water use efficiency (WUE) are far from clear. In this study, we evaluated the effects of three tillage systems (rotary tillage at 15 cm depth, RT15; subsoiling at 40 cm depth, SS40; and subsoiling at 35 cm depth, SS35) on soil pore structure, hydraulic properties, and WUE during the 2022–2024 winter wheat seasons. Results showed that the effects of SS40 and SS35 were similar in optimizing the soil pore structure and hydraulic properties. Compared with RT15, SS40 and SS35 increased the soil macroporosity ratio, the soil pore connectivity, and the soil water storage. Structural equation modeling revealed that optimized soil pore structure under subsoiling directly and positively influenced the WUE or indirectly increasing the soil water storage. As a result, compared with RT15, SS40 and SS35 increased the spike number, kernel number per spike, and 1000-grain weight, and ultimately improved the yield (35.59% and 39.32%, respectively) and WUE (36.69% and 41.55%, respectively). Overall, the results revealed the mechanism of high-efficiency water use from the perspective of pore network-based hydraulic properties, providing a theoretical basis for food security.