Abstract:

In arid irrigated regions, achieving the coordinated improvement of crop yield and water productivity (WP) remains a major challenge. Although combined organic–inorganic fertilization is widely recognized as an effective strategy, the mechanisms by which it regulates soil water and nitrogen supply to optimize crop water consumption and simultaneously enhance yield and WP remain unclear. A three-year field experiment (2023–2025) was conducted at the Wuwei Oasis Agricultural Experimental Station in China to evaluate the effects of different organic fertilizer substitution rates (NPK, 0%; OF1, 10%; OF2, 20%; OF3, 30%; OF4, 40%) on soil water–nitrogen dynamics, crop growth, water consumption characteristics, yield, WP, and economic benefits (EB). The results showed that, compared with NPK, OF2, OF3 and OF4 increased soil organic matter (SOM) and soil macro-aggregates (SMAA) while reducing soil bulk density (SBD), thereby enhancing soil water content (SWC) in the 0–60 cm soil layer, with stronger effects at higher substitution rates. OF2 significantly increased soil alkali-hydrolyzable nitrogen (SAN) in the 0–40 cm soil layer after the V6 stage and maintained a stable nitrogen supply throughout the growing season, achieving optimal coordination of soil water and nitrogen supply. Consequently, OF2 promoted crop growth, as evidenced by increased root biomass (RB) in the 0–40 cm soil layer at the R3 stage, as well as higher dry matter accumulation (DMA) and canopy coverage (CC) at the R1 and R3 stages. The increases in DMA and CC, under conditions of no significant difference in total evapotranspiration (ET), drove a redistribution of post-flowering water consumption from soil evaporation (E) to crop transpiration (T), characterized by increased T and decreased E, thereby optimizing crop water consumption characteristics and jointly improving fresh ear yield (EY), WP, and EB. Multi-objective comprehensive evaluation identified 17.68% as the optimal theoretical organic fertilizer substitution rate, reflecting the best balance among soil improvement, crop growth, water use, and economic return. This study elucidates the mechanism by which partial organic fertilizer substitution regulates soil water and nitrogen supply to optimize crop water consumption and improve WP, providing a theoretical basis and practical strategy for sustainable waxy corn production in arid irrigated regions.