EFFECT OF TOTAL CATION CONCENTRATION AND SODIUM ADSORPTION RATIO ON EXCHANGEABLE SODIUM RATIO

Abstract

Replicated analyses for each of five levels of total cation concentration showed that exchangeable sodium ratio (ESR) and sodium adsorption ratio (SAR) were linearly related by equations of the form ESR = a + b (SAR). The coefficient, b, decreased from 0.0163 to 0.0085 as total cation concentration increased from 39 to 1057 meq/L, showing that the equilibrium of exchange, as measured by ESR and SAR, is strongly affected by total cation concentration of the soil solution. A regression line, previously published by the U.S. Salinity Laboratory Staff, lies between the regression lines for 39 and 110 meq/L. Exchangeable sodium ratio can be inferred from SAR alone as long as SAR is not larger than about 20. However, the error of estimate for ESR is shown to increase with increasing SAR and total cation concentration unless the effect of total cation concentration is taken into account. This is an important factor to be considered when high-salt solutions are used to reclaim sodic soils.