Effects of decomposed straw and desulfurized gypsum on salt leaching in saline-sodic soils

Saline-sodic soil colloids contain a large number of exchangeable sodium ions,leading to soil aggregates breakdown,clay dispersion and soil pores blocking.Saline-sodic soils improvement requires two processes,providing calcium source to exchange with sodium on soil surface and removing salt through leaching or drainage.In this study,we used corn straw and desulfurized gypsum to improve the saline-sodic soil,and investigated the effect of different treatments on the desalination efficiency of saline-sodic soil during leaching.The results showed that all the treatments improved soil infiltration,and the infiltration rate was in an order of desulfurized gypsum > desulfurized gypsum + decomposed straw > control.Compared with the control,the treatments with desulfurized gypsum significantly increased the saturated hydraulic conductivity of the soil.Decomposed straw treatment would not improve soil hydraulic conductivity right in short time after start of leaching,but increased soil hydraulic conductivity after 70 d.The moisture content with decomposed straw treatment was the highest,meaning the material was with good water retention.The leachate chemical properties showed that all the treatments enhanced sodium ions leaching.The soil chemical properties showed that the salt content of each treatment significantly decreased after leaching.The soil pH with desulfurized gypsum and combined application treatments were significantly lower than those with the control and straw treatment.The contents of soil soluble sodium with all improved treatments were significantly lower than that of the control,and the contents of divalent cations such as soluble calcium and magnesium in the soil were significantly higher than that of the control.After leaching,the soil sodium adsorption ratios with all improved treatments were significantly lower than that of the control.