[Effects of drip irrigation and intercropping on soil water-salt dynamics and sorghum yield in saline-alkali land]

To mitigate the reduction of crop yield caused by soil salinization in the Ningxia Yellow River Irrigation District, we implemented an experiment with split-plot design to evaluate the effects of three drip irrigation regimes (W1: spring border irrigation 180 mm + growing-season drip irrigation 420 mm; W2: 162 mm + 378 mm; and W3: 144 mm + 336 mm) and two planting configurations (T1: sorghum monoculture; T2: sorghum-sesbania intercropping) on soil water content, salinity, desalination efficiency, sorghum growth, and yield. We applied partial least squares path model (PLS-PM) to analyze the dynamics of water-salt transport and the synergies of intercropping. Results showed that during the seedling and jointing stages, intercropping (T2) under the W2 and W3 increased soil water content in the 40-80 cm layer by 1.6%-8.5% compared to monoculture (T1). During the grouting stage, T2 under W1 and W2 significantly reduced soil salinity in 0-40 cm layer by 4.1%-35.5%. W2 was the optimal irrigation regime for salt leaching efficiency across both planting patterns. Moreover, intercropping (W2T2) enhanced sorghum growth in the pustulation period, with shoot length reduced by 13.6% compared to W2T1. Compared with T1, stem thickness of T2 elevated by 2.2%, 7.7%, and 5.5% for W1, W2, and W3, respectively. Du-ring the booting stage, sorghum under T2 showed enhanced leaf area index by 6.6% and 7.7% and chlorophyll contents (SPAD values) by 28.2% and 3.3% under W1 and W2, respectively compared to T1, while a reduced SPAD was observed under W3 treatment. Overall, T2 boosted sorghum yield by 3.9%-7.3%, with W2T2 yielding 7865.6 kg·hm^-2 and significantly higher than that of W1T2 and W3T2. Furthermore, structural equation modeling results indicated that T2 strengthened photosynthetic capacity, enhanced grain assimilate allocation, and mitigated water stress via interspecific resource complementation. The combination of sorghum-sesbania intercropping with growing-season drip irrigation 378 mm maximized salt leaching, deep-water utilization, and crop yield, offering a promising strategy for water-saving salt management and productivity enhancement in saline-alkali environment.