Subsurface Irrigation Depth Affects High-Yield Triticum aestivum Cultivation in Saline-Alkali Soils: Evidence from Soil–Microbe–Crop Interaction

Drip irrigation burial depth is a critical management factor for saline-alkali agriculture, yet its mechanisms of influencing crop productivity through soil–microbe–plant interactions remain poorly understood. To explore the regulatory effects of drip irrigation burial depth on the growth and rhizosphere microenvironment of dryland wheat in saline-alkali soil, three treatments (no irrigation control, CK; 5 cm shallow-buried drip irrigation, T5; 25 cm deep-buried drip irrigation, T25) were set up, with soil physicochemical properties, microbial community characteristics, and crop yield analyzed. The results showed that drip irrigation significantly improved soil environment and yield, and T25 exhibited superior comprehensive benefits: soil electrical conductivity was reduced by 63%, organic matter content increased by 44%, and water-salt status was significantly optimized; meanwhile, microbial community structure was altered and root nutrient uptake capacity was enhanced, ultimately achieving a yield of 5347.1 kg ha−1, 55.0% higher than CK. In conclusion, 25 cm deep-buried drip irrigation may provide advantages for wheat cultivation primarily through improved water distribution, desalination, and soil structure enhancement.