Estimation of Components of Soil Cation Exchange Capacity from Measurements of Specific Surface and Organic Matter

Abstract Cation exchange capacities of Irish soils developed from a wide range of parent materials were found to be highly correlated with organic matter content and specific surface but not with clay content. Multiple regression analysis showed that organic matter in combination with specific surface accounted for 97% of the variation in CEC whereas organic matter and clay content only accounted for 58% of the variation. The better correlation between CEC and specific surface than between CEC and clay content, is attributed to the ability of surface area measurements to reflect the presence of phyllosilicates in silt and sand fractions of soils and to the fact that these minerals have less variable surface charge densities than cation exchange capacities. It is proposed that specific surface provides a better estimate than clay content, of the mineral component of CEC for soils of varying mineralogy.