Swell-shrink potential of vertisols in relation to clay content and exchangeable sodium under different ionic environment

Surface samples of seven different Vertisols with wide variation in the electrolyte concentration and sodium saturation were studied for their swell-shrink characteristics. The soils are found to be dominantly smectitic with minor amounts of kaolinite and illite. The coefficient of linear extensibility (COLE) values of all the soil samples fall in the categories of very high (COLE >0.09) swell-shrink classes. The correlation matrix among COLE, Atterberg limits, swelling pressure (SP), free swell index (FSI) and different soil properties were determined. These parameters showed positive correlation with 2:1 swelling clay, ESP, pH and negative correlation with ECe. At the same levels of clay and ESP, the increase in electrolyte concentration would decrease the swelling. A highly significant positive correlation between the COLE and FSI, SP and VSP indicates that all these measurements can be used as predictors of swell-shrink potential of the salt-affected Vertisols.