replace the sodium with calcium and then leach the sodium out by two possible approaches for doing this: dissolve the limestone (calcium carbonate) or gypsum (calcium sulfate) al- ready present in the soil or, add calcium to the soil. If free lime is present in the soil, it can be dissolved by applying sulfur or sulfuric acid. Sulfur products reduce the pH which dissolves the lime, thus freeing up the calcium. If free lime or gypsum is not present in adequate amounts as determined by a soil test, then calcium can be added.