Extraction of Cations from Silicate Minerals During the Determination of Exchangeable Cations in Soils

Abstract The extent to which silicate minerals release Ca, Mg, Na, and K during the determination of exchangeable cations in soils by the ammonium‐acetate‐extraction procedure was evaluated. The method of exchangeable‐sodium evaluation used by the US Salinity Laboratory was employed for this study with the exception that soil samples were replaced with reference mineral samples. Amounts of cations equivalent to 0.3 to 21.8 meq/100 g were extracted from the minerals by ammonium acetate. In general, the proportions of cations extracted decreased in the order Ca + Mg>> Na> K. Because of this phenomenon, complications are expected to occur in the evaluation of exchangeable Ca and Mg in arid‐land soils, but not for exchangeable Na except under unusual circumstances. The latter circumstances are described and the general extent of error that may occur is estimated.