Coupled Drip Irrigation and Microbial Inoculants Enhancing Alfalfa Yield and Optimizing Rhizosphere Fungal Communities in Arid Saline Soils

Water scarcity and soil salinization constrain sustainable alfalfa (Medicago sativa L.) production in arid Xinjiang, China. Although drip irrigation and microbial inoculants improve soil quality and crop productivity, their synergistic effects on rhizosphere ecosystems remain unclear. This study investigated the effects of drip irrigation combined with composite microbial inoculants on rhizosphere soil properties, fungal communities, and alfalfa yield. A two-factor randomized block experiment was conducted with four irrigation levels (6450, 7050, 7650, and 8250 m3/ha) and three inoculant rates (0, 0.5, and 1.0 m3/ha), with conventional irrigation (9750 m3/ha) as the control. We analyzed soil properties, fungal communities, and ecological relationships using high-throughput sequencing and partial least squares path modeling. Combined irrigation and inoculation improved soil nutrient availability, reduced rhizosphere salinity, and enhanced fungal network stability. Moderate irrigation combined with inoculation increased soil alkali-hydrolyzable nitrogen, available phosphorus, and available potassium, while W4J2 achieved the highest yield. Irrigation explained more fungal community variation (33.2%) than inoculation (18.6%), with salinity and nutrients as key drivers. Path analysis revealed that irrigation directly promoted yield, whereas inoculation indirectly enhanced productivity through soil improvement and fungal regulation. Integrating drip irrigation with microbial inoculants provides an effective strategy for sustainable forage production in saline arid regions.