In soils with weak structure resulting from an imbalance between Na+ and Ca2+, increasing soluble Ca2+ can improve aggregation, water infiltration, soil drainage, and root penetration. Acid or acid-forming amendments are acceptable additives for increasing soluble Ca2+ in calcareous soils only. In all soils, regardless of pH, gypsum is a good Ca2+ additive when Ca2+ is needed. Calcium sulfate anhydrite will also supply Ca2+, but it will dissolve more slowly than gypsum. With either gypsum or calcium sulfate anhydrite it is important to know the composition of the material you select, which can vary considerably depending on source. Soil analysis can help determine how much of these materials to apply to your soil.  

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