The certified values were determined by Dutch standard methods (NEN 57.; NEN 64. series).Certified valuesAs. 8.0 mg/kgFe .21 mg/kgP. 0.73 mg/kgCa . 23934 mg/kgN .0.73 mg/kgZn . 79.0 mg/kgCu . 17.0 mg/kgMn.208.1 mg/kgIndicative values for Al, Ba, Cd, Cr, C