Comparison of three methods of measuring surface area of soils

Surface area (SA) is an important property of soils, but different methods can give widely different estimates of SA, and of the contribution of organ ic matter to SA. This study was undertaken to compare two common methods of measuring SA (EGME [ethylene glycol monoethyl ether] and N-2 sorption) wit h SA estimates using H2O sorption on selected Saskatchewan soils; some soil s from Kenya were included to show the impact of clay mineralogy. For the S askatchewan soils, the three estimates of SA were highly correlated to each other and to clay content, but SA EGME was 2 to 3 times SA H2O and 7 to 52 times SA N-2. Organic matter did not appear to contribute to SA EGME, incr eased SA H2O and decreased SA N-2. Clearly the three methods differ in thei r access to internal and external surface area and this should affect their utility as indices of the sorptive capacity of field soils.