Water and salt transport in sand-layered soil underevaporation with the shallow under ground water table

Considering the fact that most soil profiles assume layered structure and that most bare soils are exposed to the atmosphere when salt accumulation in the surface soil was very rapid in northwest region of China. The impacts of sand position, sand thickness and sand porticle distribution of sand-layered soil with the shallow ground water table on water and salt transport were analyzed through the experimental columns. The results showed that water and salt transport was accelerated when the distance between the low boundary of sand layer and the water table was zero, and that it was depressed when the distance was more than 10 cm. The controlled amount for the sand layer against the water and salt transport was 70%～80% when the distance was more than 35 cm. The effect of the sand layer against the water and salt transport decreased with the increase of the evaporation duration except for the treatment with 35 cm distance, and the effect of the sand layer against salt transport was more than the effect against water transport at the same evaporation duration. In addition, the effects against water and salt transport were intensified for the treatments with the thicker sand layer and the worse sand distribution. The study is very important for preventing soil from secondary salinization and guiding irrigation and drainage.