Effect of Dilute Salt Solutions on Chernozem Soil Estimated Through the Hydration Properties of the Colloids

Research Institute of Soil Science and Agricultural Chemistry of Hungarian Academy of Sciences, Budapest Received 28 July 1972 Alkali soils containing illite with high exchangeable K are reported to be less susceptible than those containing montmorillonite to the adverse effect of sodium on their physical properties, Besides, that the adsorption complex of the former attains comparatively lower Na saturation than the latter, the other probable reason for this discrepancy seems to be the inherent difference in the degree of hydration of Na ions owing to differences in the bonding force available on the mineral surfaces. This aspect which is of practical value in understanding salt affected soils where these two minerals are dominant, was studied, Samples of chernozem soil (containing initially illite and montmorillonite) enriched with three levels of pure illite and bentonite were leached for a number of times in columns with single sale solutions of Na2CO3, NaCl and MgCl2, and their clay fractions were studied by differential thermal and X-ray methods. Illite treated samples adsorbed less moisture at maximum hygroscopicity than montmorillonite treated ones, and the energy needed to drive off the :moisture from the illite treated samples, as indicated by differential thermal analysis, was also relatively higher than for montmorillonite samples. Basing on the location and force of sodium bonding on the surfaces of illite and montmorillonite, it was concluded that sodium ions had a tendency towards less hydration on illite than on montmorillonite