Subsurface fertigation modifies soil–plant–water interactions to improve productivity of cotton–wheat systems under reduced tillage

Excessive reliance on surface flood irrigation accelerates groundwater depletion and degrades soil physical conditions in intensive cropping systems, yet the mechanisms by which irrigation–fertigation strategies influence soil–plant processes under reduced tillage remain poorly understood. We investigated how subsurface drip fertigation (SDF) alters soil physical properties, plant physiological functioning, and system productivity in a low-tilled cotton–wheat rotation over two growing seasons. Subsurface fertigation significantly moderated soil compaction, reducing soil bulk density in the upper (0–15 cm) and subsurface (15–30 cm) layers compared with surface flood irrigation, indicating improved soil structural conditions under localized water and nutrient delivery. Enhanced soil conditions under SDF were associated with improved leaf-level gas exchange, including higher photosynthetic rate, transpiration, and stomatal conductance, which collectively translated into greater crop productivity. Among SDF configurations, lateral placement at 25 cm depth combined with closer emitter spacing (30 cm) optimized root–zone resource availability and physiological performance. Fertigation strategies delivering nitrogen and phosphorus in multiple split applications further strengthened wheat crop responses, highlighting the role of synchronized nutrient–water supply in regulating system productivity. Our findings demonstrate that subsurface fertigation improves soil–plant interactions and resource-use efficiency under reduced tillage, offering a viable pathway to enhance productivity while mitigating pressure on groundwater resources in intensive cropping systems.