The preparation of an air‐dry river‐clay soil as reference soil material for pH and extractable nutrients with a 0.01 M calcium chloride (CaCl2) solution and the homogeneity testing are described. Recommended values for pH and the concentrations of ammonium‐nitrogen (NH4‐N), total soluble nitrogen (N), phosphorus (P), sodium (Na), potassium (K), and magnesium (Mg) using the unbuffered 0.01M CaCl2are given. With respect to nitrate‐nitrogen (NO3‐N), the sample proved not to be sufficienctly homogeneous. The certified soil sample has also been used as a sample in the International Soil‐Analytical Exchange (ISE), a continuous proficiency testing scheme. The values found by the ISE laboratories compared well with the certified values.