A simple method to determine the reactivity of calcium carbonate in soils

Determination of soil carbonate is important for numerous chemical and physical soil processes in arid and semi‐arid zones. Here, we modify a conventional method to more easily determine active CaCO3 (ACC) fraction in soils. Unlike the conventional method where the oxalate used up after reaction with carbonate is determined by titration with KMnO4, the proposed method uses the difference between total carbonate analyzed before and after reaction with oxalate to determine ACC. The method compared well to the conventional approach; the procedure was faster, did not require KMnO4, and appeared to be unaffected by exchangeable Ca. The proposed method is well‐suited for samples across a wide range of total carbonate. Core Ideas A modification of the ammonium oxalate procedure is proposed to determine the reactivity of soil carbonate. The method compares well to the conventional approach but is simpler and faster to implement. The proposed method appears to be less sensitive to errors due to the presence of exchangeable Ca.