Assessment of soil response to exchangeable sodium percentage by consistence and water retention properties

•Sodium smectite had the greatest swelling and kaolinite had minimal swelling.•Soil containing smectite increased in swelling from ESP.•Smectitic soils can be identified by the effect of ESP on soil swelling properties.•Water retention and liquid limit were the most responsive to solution ESP. The use of low-quality water for irrigation is expected to keep increasing worldwide, which increases the risk of soil degradation. The response of soil to irrigation waters with excessive sodium depends on the soil clay behavior. Soil physical properties that can distinguish smectitic soils from non-smectitic soils could identify soils that are sensitive to exchangeable sodium. This study explores the use of Atterberg limits, coefficient of linear extensibility (COLE) and soil water retention as possible properties to determine if a soil is sensitive to exchangeable sodium. Soils used were synthetic soils prepared from mixtures of silt and clay minerals, and six natural soils. Atterberg limits, COLE and soil water retention was measured at ESP values of 0, 50 and 100% on these soils. Multiple linear regression functions were developed to predict soil liquid limit, plasticity index, COLE, and soil water retention at −336 cm H2O. The liquid limit, and COLE increased as the amount of sodium-saturated smectite increased in the synthetic soils. The liquid limit, COLE and water retention at matric potentials greater than −336 cm of H2O increased on smectite clay dominant soils when elevated ESP was combined with low salinity. The liquid limit increased from 49 to 67 on average and −336 H2O water content increased from 38 to 70% on average between 0 and 100% ESP treatments on the four smectitic soils. On a kaolinitic soil liquid limit decreased from 56.1 to 51.8 and −336 H2O water content increased from 33.7 to 35.9% between the ESP 0 and 100% treatment. Liquid limit increased from 188 to 679 and COLE increased from 0.47 to 1.19 mm mm−1 between calcium smectite (fullers earth) and sodium smectite (Wyoming bentonite), whereas liquid limit decreased from 56 to 39 and COLE decreased from 0.195 to 0.104 mm mm−1 between calcium and sodium saturated kaolinite. Plasticity index increased by 75% between the ESP 0 and ESP 100 treatments on the smectitic soils, whereas there was a 260% increase in plasticity index between fullers earth and bentonite. The root mean squared error that liquid limit could be predicted with was 3.3 plastic limit was 2.4, COLE was 0.036 mm mm−1, and 1/3rd