This method quantitatively determines the concentration of K, Na, B, S, Ca, and Mg in the saturated paste extract using Inductively Coupled Plasma Emission Spectrometry (ICP-AES). Sulfur results are assuming that all sulfur present is in the sulfate from. Sulfate uptake by plants can be related to the sulfate concentration in the saturated paste extract. Plant tolerance to soil boron can be related to the boron concentration in the saturated paste extract. K, Na, Ca and Mg are generally the dominant cations in the saturated paste extract of soils. Concentration of soluble Na, Ca, and Mg is used to determine the sodium adsorption ratio (SAR) of soils. Extract solutions containing greater than 10,000 mg/L (1.0% w/v, estimated from ECe) will require dilution since solutions of this salt concentration may impair instrument operation.
Knudsen, D., Peterson, G. A. and Pratt, P. F. 1982. Lithium, sodium and potassium. pp. 225-246. In: A. L. Page et al. (ed.) Methods of soil analysis: Part 2. Chemical and microbiological properties. ASA Monograph Number 9.
Soltanpour, P. N. Benton Jones, Jr., J. and S. M. Workman. 1982. Optical emission spectrometry. p. 29-65. In: A. L. Page et al. (ed.) Methods of soil analysis: Part 2. Chemical and microbiological properties. Monograph Number 9 (Second Edition). ASA, Madison, WI.