Analysis of driving factors of soil salinity in Southern Xinjiang irrigation areas under dry-sowing and wet-emerging conditions

Dry-sowing and wet-emerging (DSWE) is widely practiced in the oasis irrigation districts of southern Xinjiang for its simultaneous benefits of water conservation and salt regulation. However, its effectiveness exhibits strong spatial heterogeneity, and traditional global regression models fail to capture the localized influence of environmental factors on surface soil salinity. For the first time, this study introduces Multiscale Geographically Weighted Regression (MGWR) to quantitatively disentangle the spatially varying impacts of topography, groundwater, soil properties, and vegetation on topsoil (0–30 cm) salinity. Using 87 high-density sampling sites and 261 layered soil samples from the Xiaohaizi Irrigation District, we employed MGWR to determine the direction, magnitude, and spatial bandwidth of each factor’s effect. The results show that:(1) MGWR achieved localized R² values of 0.52–0.91, significantly outperforming global OLS regression (R² = 0.41) in terms of explanatory power, and effectively capturing the spatial variability of soil salinity in arid irrigated regions.(2) Groundwater salinity emerged as the dominant positive driver, with a mean coefficient of 0.399 and a peak of 0.861 in the northwestern part of the district (bandwidth: 2.1 km), directly delineating high-risk zones for salt accumulation at the surface.(3) Elevation and groundwater depth exhibited the strongest negative effects in the northeastern low-lying areas (coefficients: −0.164 and −0.179, respectively), suppressing salt accumulation. Slope showed a weak positive effect in the southern gentle-slope region, suggesting that under shallow irrigation in DSWE systems, ponding and secondary evaporation may amplify the topographic influence on salinization.(4) Fractional vegetation coverage significantly suppressed salinity only in low-coverage areas, while its effect was diluted in high-coverage zones, indicating a threshold-type regulation between greenness and salinity.Based on these spatial mechanisms, a zoning- and factor-specific salt control strategy is proposed: We recommend implementing well drainage and freshwater irrigation to dilute groundwater in the northwest, intensifying subsurface drainage to maintain a groundwater depth ≥ 0.8 m in the northeast, and optimizing the lower irrigation limit under DSWE in the southern gentle-slope zone to reduce ponding duration. This study provides a methodological paradigm for spatially explicit salinity management in arid oasis regions and offers a novel application case of MGWR in agricultural hydrological process analysis.。