This International Standard specifes a rapid method for the determination of the potential rate of ammonium oxidation and inhibition of nitrifcation in soils. This method is suitable for all soils containing a population of nitrifying microorganisms. It can be used as a rapid screening test for monitoring soil quality and quality of wastes, and is suitable for testing the effects of cultivation methods, chemical substances [except volatiles, i.e. H > 1 (Henry’s constant)], extracts of biosolids and pollution in soils.