Effect of Soil Texture on Water and Salt Transport in Freeze-Thaw Soil in the Shallow Groundwater Area

Research on the variation in soil water, heat, and salt in unsaturated zones during the freeze-thaw process has great significance in efficiently utilizing water resources and preventing soil salinization. The freeze-thaw field experiment was carried out with the lysimeter as the test equipment to analyze characteristics of the soil freeze-thaw process, profile water content, main ion content, and salt content of three textured soils with the groundwater table depth of 0.5 m. The results showed that the soil temperature gradient and freezing depth were greater as the average soil particle size increased. The increment of water content at the depth of 0 to 30 cm in sandy loam and loamy sand decreased by 40.20 similar to 93.10% and 28.14 similar to 65.52% compared with that in sandy soil, and the average increment of salt content at the depth of 0 to 30 cm decreased as the average soil particle size increased during the freeze-thaw period. The average content of Ca2+, Na+, Cl-, and SO42- in loamy sand and sandy soil decreased by 4.37 similar to 45.50% and 22.60 similar to 70.42% compared with that in sandy loam at the end of the freeze-thaw period, and the correlation between soil salt content and water content decreased with the increase in the average soil particle size. The research results can provide a theoretical basis for soil salinization prevention and crop production in shallow groundwater areas.