This International Standard specifies a method for the determination of the cation exchange capacity (CEC) at the pH of the soil and of the determination of the content of exchangeable sodium, potassium, calcium and magnesium in soil. This International Standard is applicable to all types of air-dried soil samples; pretreatment according to ISO 11464 is recommended. NOTES 1 The method described suffers from interference from calcium as calcite or gypsum in the sample. Also, the presence of any soluble salts gives values for the exchangeable cations that are higher than the actual exchangeable amounts [3],[4]. 2 Measurement of the specific electrical conductivity of the soil samples according to ISO 11265 will indicate if the soil samples are affected by salt