Deep-injected straw incorporation enhances soil quality and buffers wheat yields against water deficit

Intensive agriculture has induced widespread soil degradation and water scarcity, threatening global food security. Straw incorporation is widely considered for soil quality improvement, yet its interactive effects with water availability on crop yield remain unclear. Here, we investigated the integrated effects of five straw management practices—straw removal (SR), straw mulching (SM), straw incorporation into surface soil (SI), deep-ploughed straw incorporation (DP-SI), and deep-injected straw incorporation (DI-SI)—under two irrigation strategies (conventional irrigation and water-saving irrigation) on soil quality, water productivity, and wheat yield. DI-SI increased soil organic carbon and available nutrients (ammonium, nitrate, and available phosphorus) contents while reducing bulk density, resulting in a higher soil quality index than the other treatments. These benefits were most pronounced in the subsoil and remained consistent under both irrigation regimes. Under conventional irrigation, DI-SI increased wheat yield by 4.9%-12.3% compared to the other treatments, whereas under water-saving irrigation it also increased yield by 23.7% on average. SM achieved the highest water productivity under conventional irrigation due to reduced actual evapotranspiration. In contrast, under water-saving irrigation, DI-SI exhibited the highest water productivity, primarily attributed to its high yield. Moreover, DI-SI exhibited a lower yield response factor to water deficit than other treatments, indicating enhanced drought tolerance. Our findings suggest that adopting DI-SI can contribute to sustainable agriculture and enhance crop yield particularly in water-limited scenarios, offering a potential pathway to mitigate soil degradation, water shortages, and food insecurity.