Exchangeable Sodium Percentage, ESP, and/or Sodium Adsorption Ratio, SAR

Exchangeable Sodium Percentage (ESP) is used in the classification of saline and alkali soils or to determine if a sodium hazard exists. This method requires the determination of Cation Exchange Capacity (CEC) and exchangeable sodium percentage (ESP). If soluble sodium is present, the exchangeable value is corrected by analysis of sodium (Na) in a saturated extract (1).  Sodium Adsorption Ratio (SAR) is used to estimate or predict ESP by analyzing for Na, Ca, and Mg in a water-saturated soil extract (2).  SAR is commonly determined on irrigation water to classify the sodium hazard.

(See Method Reference No. 17)

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