The sum of exchangeable bases plus total soil acidity at a specific pH, values, usually 7. 0 or 8. 0. When acidity is expressed as salt extractable acidity, the cation exchange capacity is called the effective cation exchange capacity (ECEC) because this is considered to be the CEC of the exchanger at the native pH value. It is usually expressed in centimoles of charge per kilogramme of exchanger (cmolckg-1) or millimoles of charge per kilogramme of exchanger.