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

摘要

In countries with arid and semiarid regions, decreases in agricultural production due to excessive salts is a very serious problem. Moreover, because environmental problems due to air pollution have caused much damage to the ecosystem in China, it is necessary to rapidly introduce flue gas desulfurization (FGD) processes. We have reclaimed alkali soil by using gypsums that are by-products of FGD processes, and good soil reclamation has been confirmed. Based on this research background, we examined the mechanism of alkali soil reclamation by gypsum from the point of view of the change in hydraulic conductivity and the solute transport in soil. We investigated the salts transport mechanism by using a soil column equipped with a tensiometer and a four-electrode sensor. 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 to elucidate the soil reclamation mechanism. Initial Na leaching was confirmed, both by four-electrode sensor measurement and quantitative analysis of leachate. Lastly, the correlation between pH, EC, cations (Na+, Ca2+, Mg2+ and K+) and Cl-concentration in leachate was investigated. Correlation coefficients between all the parameters were confirmed, to different levels of significance (P value < 0.01**). The Penman -Monteith equation was used for the water content balance and the evapotranspiration in the paddy field was predicted, taking into consideration the meteorological data and the test conditions. The results predicted that about 103% and 76% of complete salt leaching will be attained by the end of October, 2008 for the 0.5 wt% and 1.0 wt% applications, respectively.