Cation Exchange Capacity, CEC, by Direct Method

CEC is determined when 3 g of air dried soil (1 g peat) is leached with 60 mL 1 M NH4OAc, pH 7, to saturate exchange sites with ammonium ions. Excess free ammonium ions are rinsed from the soil with isopropyl alcohol. The remaining ammonium ions held on cation exchange sites are replaced by leaching the soil with successive aliquots of a solution of 10% KCl acidified to 0.005 N HCl. Ammonium is determined on the KCl leachate by colorimetry on a Lachat QuikChem 8500 Flow Injection Analyzer using the salicylate/nitroprusside method.

(See Method References No. 26 & 27)