Salts Transport in Alkali Soil Reclamation by Gypsum and Prediction of Na Leaching in Field in China

Abstract

We examined the mechanism of alkali soil reclamation by gypsum from the change in hydraulic conductivity and the solute transport in soil. Solute transport mechanism was investigated by using a soil column equipped with tensiometers and four-electrode sensors (FES). Moreover, the pH and EC were measured, and quantitative analysis of the cations (Na⁺, Ca²⁺, Mg²⁺ and K⁺) and the anion Cl^- in leachate was carried out. As a result, the initial Na leaching was confirmed by FES measurement, EC of leachate and quantitative analysis of leachate. Correlation coefficients between all the parameters (pH, EC, cations (Na⁺, Ca²⁺, Mg²⁺ and K⁺) and Cl^-) were confirmed, to different levels of significance (P value ‹ 0.01).
Lastly, the water content balance and the evapotranspiration by Penman-Monteith method in the paddy field predicted the soil reclamation time, taking into consideration the meteorological data and the column experimental results. Consequently, it could be predicted that all salts in case of 0.5 wt% application and almost salts (97%) in case of 1.0 wt% application are leached by the end of October.