Effect of salinity and sodicity on water retention of montmorillonite
2006
Ahmad, M.M.(Water Resources Research Inst., Islamabad (Pakistan)) | Karube, J.
Irrigation with used low quality water in arid and semiarid regions may damage soil structure due to clay dispersion. We investigated water retention of montmorillonite affected by salinity and sodicity, which are indicated by electrical conductivity (EC) and sodium adsorption ratio (SAR), respectively. Experiment was carried out with solutions of NaCl 2, 20, 50 mol m(-3), combined with SAR 5, 10, 20. When NaCl concentration was 2 mol m(-3), the clay showed high water retention at all SAR owing to low EC. At NaCl 20 mol m(-3), the sample SAR 5 showed significantly low water retention compared to SAR 10 because EC of the former solution was high. Water retention increased with increasing SAR when the system was in coagulative condition, and no difference was found in water retention if the system was in dispersion condition. In coagulative condition, both EC and SAR affected the water retention, and lower water content was observed at higher EC and lower SAR. For montmorillonite, this lower water retention might lead to an aggregated structure. Thus, combined effect of salinity and sodicity was found important for controlling physical properties of montmorillonitic soils.
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