This procedure is identical to Method 15B1 except that a calculation based on the amount of water soluble Cl– in the soil is used to adjust for the apparent level of exchangeable Na+ present in the same soil. This approximate correction for soluble Na+ is an alternative to chemical pre-treatment when EC (1:5, soil/water) exceeds ≈0.3 dS/m and NaCl is known to be the dominant soluble salt.
Determine exchangeable bases (Method 15B1) and water soluble Cl– in the soil (Method 5) and continue as described in Method 15A3 and 15B1.
Determine and report exchangeable cations and CEC (cmolc/kg), expressed on an oven-dry soil basis. Refer to Method 2A1 for guidance with regard to this soil moisture calculation.