x-K, x-Na, x-Ca, x-Mg.
This is a soil fertility test. This method quantitatively determines the concentration of dissolved Cations in the soil saturation paste extract using atomic absorption spectrometry (AAS) or Inductively Coupled Plasma Emission Spectrometry (ICP-AES). The relationship between cation solution concentrations and exchangeable cations in the soil, is used to estimate exchangeable sodium percentage (ESP) from the SAR. The method detection limit for these cations is approximately 0.02 mmolc/L on a solution basis and it is generally reproducible within ± 7%.