Abstract:Long-term irrigation of low quality water carrying large amounts of salt causes a significant degradation risk of soil physicochemical properties. The determination of difference in the influence of salinity on soil water characteristic curve of five subtropical soils, such as clay fluvo aquic soil, sandy fluvo aquic soil, red soil, purple soil and paddy soil, were investigated and these soils treatments with four different NaCl solutions (0g/L, 5g/L, 10g/L and 15g/L) were prepared to obtain the soil water characteristic curves of drying processes by the pressure membrances method. The optimal models that described soil water characteristic curves of different salt concentration dealt soils were determined by RETC software and mathematical statistics method. The results showed that the sodium salt can improve the soil water holding capacity, and special significant effect for soil with high content clay. Available water contents of clay fluvo aquic soil, sandy fluvo aquic soil and red soil treated with NaCl solutions treatments were maximally reduced by 40.8%, 30.5% and 31.5%, respectively, and available water contents of purple soil and paddy soil were maximally increased by 45.7% and 28.9%, respectively. The Brooks and Corey model was the optimal model to describe the soil water characteristic curves of soils with less clay or treatments with salt solution of low concentration. The Dual-porosity-Mualem model was the optimal model for high clay content of the soils treated with salt solution of high concentration. The research results can serve as reference for the secondary salinization of soil, reclaimed water irrigation, calculation of water and salt transport in southern subtropics.
