Influence of ionic strength on sodium-calcium exchange of two temperate climate soils

Salt-affected soils have been studied extensively with respect to their Na-Ca exchange properties. These studies have focused on soil environments of the arid West. However, because of irrigation and oil well brine discharges in the temperate region of the U.S. there is need to understand sodicity behavior of such soils. In this study, two Kentucky soils (Pembroke and Uniontown) at the 0-10 cm depth were studied to evaluate the influence of ionic strength (I) and sodium adsorption ratio (SAR) on cation selectivity coefficients. The data showed that both soils exhibit at least two classes of exchange sites and in general the apparent affinity for Na+ increased when solution ionic strength increased. Furthermore, both soils under all three ionic strengths tested showed greater affinity for Na+ than the average agricultural saline soil of the arid West. The data suggested the need for establishing critical salt dispersion thresholds for temperate climate soils and developing effective brine management approaches.