Sandy soil layer alleviates down-to-top enrichment of salts in saline fields

摘要

Down-to-top enrichment of salt components along with soil profile is widely recognized as a critical driving force of soil salinity.We investigated vertical transportation of water and salt in vertical soil profile in two adversely salt contaminated fields at Xinjiang, northwest China during summer.Two separate experiments were designed as: 1) to conduct comparative study in the sites with and without sandy soil layer (in the depth of 60-100 cm) was conducted to reveal the effect of sandy soil layer on salt enrichment;2) to further reveal the mechanism of sandy soil layer affecting water and salt movement using different coverage on topsoil including non-mulching,straw mulching and plastic mulching in the fields with sandy layer.The data indicated that the minimum soil moisture, electrical conductivity (EC) and total soil salt content were observed in sandy soil layers and the maximum topsoil temperature was found in plastic mulching treatment.At the end of the strong evaporation period (30th, August), the top soil (0-60 cm) salt content increased by 73.42％ compared with the early strong evaporation period in the site without sandy soil layer;in the site with sandy soil layer, the top soil salt content increased by 21.27％ and 8.01％ with non-mulching and straw mulching treatments, while the top soil salt content decreased by 24.89％ with plastic mulching treatment.The ratio of total cations to anions (Σcations/Σanions) in the top soil with sandy soil layer was 10.6∶1, the data slightly lower than the site without sandy soil layer.It suggested that the sandy soil layer strongly inhibited the salt down-to-up enrichment and decreased the loss of the electrical charge balance degree.The sandy soil layer with plastic mulching was found to be the best combination to inhibit upward enrichment of salt ions but improve water permeability.Our results suggested that sandy soil layer settings with plastic mulching might be a critical technical strategy to manage salt contaminated fields in cold and arid