This is a soil salinity test. Cation exchange capacity (CEC) is the measure of a soil to retain readily exchangeable cations which neutralize the negative charge of soils. This method involves saturation of the cation exchange sites with ammonium. This method maybe poorly suited to soils containing carbonates, vermiculite, gypsum and zeolite minerals. The method detection limit is approximately 1.0 cmol/kg and is generally reproducible within ± 10%.