Construction and Application of Soil–Water Characteristic Curve Model Considering Water Mineralization Degree

This study investigated the effects of irrigation water salinity on the soil–water characteristic curve (SWCC) using soil samples collected from a typical irrigated area in Yingjisha County, southern Xinjiang. The SWCC was determined experimentally via centrifugation. The correlation degree among influencing factors was evaluated, and a goodness-of-fit assessment of mainstream traditional SWCC models was conducted using MATLAB 2021a. A modified Van Genuchten (VG) model incorporating the influence of irrigation water salinity was developed. The accuracy and reliability of the proposed model were validated through soil column infiltration experiments and numerical simulations. The results demonstrated that the original VG model provided the best fit for loam soils in southern Xinjiang, albeit with non-negligible deviations, indicating the need for further refinement. Significant correlations were identified between soil characteristic indices and model parameters, ranked in descending order of influence as follows: soil dry bulk density > clay content > inorganic salt content > silt content. Soils with higher clay and silt contents, along with greater bulk density, exhibited enhanced water retention capacity, resulting in a flatter SWCC. Although increased irrigation water salinity initially improved the soil’s water absorption capacity, the rate of enhancement gradually diminished with further increases in salinity, ultimately leading to a reduction in overall water retention performance. This study provides a theoretical foundation for the prevention and amelioration of saline soils and also supports the efficient utilization of water resources.