GATE 2021 AG – Question 31
Saturated soil extract contains Mg²⁺5.68,Na⁺9.90,HCO₃⁻11.20 meq/L. HCO₃⁻/Ca²⁺=2.8. Find sodium adsorption ratio, to two decimals.
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Correct answer: 4.50 to 4.50
Explanation
Calcium concentration=11.20/2.8=4.00 meq/L. Then $SAR=Na/\sqrt{(Ca+Mg)/2}=9.90/\sqrt{(4+5.68)/2}=9.90/2.20=\mathbf{4.50}$. All concentrations are already in equivalent units.