Rapid method for the determination of cation-exchange capacity of calcareous and non-calcareous soils

Abstract ?Compulsive? exchange takes place between a barium-soil and magnesium sulphate solution because Ba2+ ions are removed from solution by precipitation of barium sulphate. This phenomenon provides a basis for the very convenient routine method for cation-exchange capacity determination in soils described here. An EDTA titration is used to measure the amount of magnesium exchanged from a standard solution by a Ba-soil, which enables the cation-exchange capacity to be calculated. Advantages of the method are its speed and that the sample does not have to be washed exhaustively, so avoiding possible hydrolysis. It compares favourably with standard A.O.A.C. procedure and is much more widely applicable. Soils rich in organic matter, e.g., peats, or with much calcium carbonate, can be handled without difficulty.