Soils having different values of permanent charge (CECp), variable charge (CECv), and anion‐exchange capacity (AEC) were treated with hydroxyl, sulfate and hydrogen saturated exchange resins. The AEC was then principally OH‐ or SO42‐ saturated while CECp was principally saturated with aluminohydronium and CECv with covalently bound H. To these systems were added increments of Ca(OH)2 and the release of SO42‐, Ca2+ sorption efficiency, pH, and conductivity measured. Soils containing sorbed SO42‐ had lower Ca2+ sorption efficiency, higher lime requirements, lower pH's and higher specific conductivities than those containing sorbed OH‐. These effects were the result of replacement of sorbed SO42‐ by OH‐ according to the reaction: Soil‐SO4 + Ca(OH)2 → Soil‐(OH)2 + CaSO4