SAR and ESP Parameters

To assess the potential toxicity of sodium in the soil-water system, the SAR is used. The SAR is determined by obtaining soil solution from the soil after saturating it with water, removing the solution by vacuum, and analyzing it for Na, Ca and magnesium (Mg) in milligrams per liter. The following formula is then used to estimate the SAR  

The SAR magnitude reflects the quantity of sodium on the exchange sites of the soil. Most arid-region soils with SAR values of 15 have approximately 15% of their CEC loaded with sodium. This sodium load is known as the exchangeable sodium percentage or ESP. Soils with an ESP greater than 15 would be considered unproduc- 

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