Dissolution Rate of Gypsum in Sodic Soils

Gypsum, one of the most common amendment for sodic soils, is known to have very low solubility in soils. But the leaching studies in columns showed that dissolution of gypsum was enhanced manifold in artificially prepared sodic soils. It increased with increase in ESP and amount of gypsum mixed in the soil. The dissolution was maximum in the soil with CO₃²⁻ dominating anion followed by HCO₃⁻ and Cl⁻ in that order. The maximum dissolution was four fold that of the saturated gypsum solution. The efficiency of gypsum dissolution (% of the total dissolved) increased with increase in ESP and decrease in the amount of gypsum mixed in the soil. The Ca-Na exchange and precipitation of Ca by carbonates increased the dissolution of gypsum.