Leaching Requirement, Salinity & Drainage Water Quality
Subtopic: Sodium Adsorption Ratio (SAR)
Question Statement:
A chemical analysis of irrigation water gives the concentration of cations: $\text{Na}^+ = 6.0\text{ meq/L}$, $\text{Ca}^{2+} = 3.0\text{ meq/L}$, and $\text{Mg}^{2+} = 1.0\text{ meq/L}$. The Sodium Adsorption Ratio ($SAR$) of the water is ________ (round off to two decimal places).
Answer Key:
4.24
Step-by-Step Solution & Explanation
The Sodium Adsorption Ratio is defined as:
$SAR = \frac{\text{Na}^+}{\sqrt{\frac{\text{Ca}^{2+} + \text{Mg}^{2+}}{2}}}$
Substituting concentrations in $\text{meq/L}$:
$SAR = \frac{6.0}{\sqrt{4.0/2}} = \frac{6.0}{\sqrt{2.0}} = \frac{6.0}{1.4142} = 4.24$