# Irrigation water having Sodium Absorption Ratio (SAR) of 12 is classified as

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Irrigation water having Sodium Absorption Ratio (SAR) of 12 is classified as
1. low sodium water
2. Medium sodium water
3. high sodium water
4. very high sodium water

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Correct Answer - Option 2 : Medium sodium water

Explanation

SAR of 12 represents Medium Sodium Water

Sodium-ion in small amounts is good for plants. But excess sodium ion creates the problem for both plant and soil. Excess sodium contributes to salinity and it is toxic for some sensitive crops.

Soil with high sodium content becomes very plastic in nature in the wet stage, which shows low permeability and poor aeration.

This excessiveness of sodium ion is measured in terms of sodium absorption ratio (SAR).

${\rm{SAR}} = \frac{{\left[ {{\rm{N}}{{\rm{a}}^ + }} \right]}}{{\sqrt {\frac{{\left[ {{\rm{C}}{{\rm{a}}^{2 + }}} \right] + \left[ {{\rm{M}}{{\rm{g}}^{2 + }}} \right]}}{2}} }}$

Where,

[Na+] = concentration of sodium ion in milli-equivalent per liter

[Ca2+] = concentration of calcium ion in milli-equivalent per liter

[Mg2+] = concentration of magnesium ion in milli-equivalent per liter

 SAR Type of water 0 - 10 Low sodium 10 -18 Medium sodium 18 - 26 High sodium > 26 Very high sodium