235 POTASSIUM, SODIUM, CALCIUM, MAGNESIUM, BORON ANDSULFATE-SULFUR IN SATURATED PASTE EXTRACT
Saturated Paste Extract: K, Na, Ca, Mg, B and SO4-S
Amounts of soluble Ca, Mg, B and S in the saturated paste extract by ICP-AES. Amounts of soluble K and Na in the saturated paste extract by AES.
Summary: 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) for Ca, B, S and Mg and flame Atomic Emission Spectrometry (AES) for K and Na. 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.
| Element | MDL |
| B | 0.05 mg/L |
| Ca | 0.10 meq/L |
| K | 0.1 mg/L |
| Mg | 0.10 meq/L |
| Na | 0.10 meq/L |
| S | 0.1 mg/L |