Atterberg limits and shrink/swell capacity of soil as indicators for sodium sensitivity within a gradient of soil exchangeable sodium percentage and salinity

摘要

Soil sodification and salinization present a global soil degradation risk to agricultural production since they affect soil hydraulic properties. Soils containing smectite clays have been found to be most sensitive to sodicity although little research exists directly relating sodicity to clay swelling under varying levels of salinity and Exchangeable Sodium Percentage (ESP). The goal of this study is to determine whether soil swelling related measurements can be a proxy to determine soil sensitivity to exchangeable sodium. This study examined the response of three smectitic soils treated with salt solutions having concentrations ranging between 5 and 40 mmol(c) dm(-3) and ESP levels between 0 and 50% to create differing degrees of sodicity. Whole soil Atterberg limits and the coefficient of linear extensibility (COLE) were measured prior to and after treatments. Liquid limit, plasticity index and the coefficient of linear extensibility increased for all three soils after treatment with a salt concentration of 5 mmol(c) dm(-3) at an ESP of 25 and 50% and 10 mmol(c) dm(-3) at an ESP of 50%. Comparing liquid limit of low salinity treatment at 50% ESP to low salinity 0% ESP revealed the presence of swelling smectite clay and the sensitivity of the soils to sodicity and a soil measurement to identify soil sodicity risk.