ISO 25475:2016 specifies a method for the determination of the ammoniacal nitrogen content in fertilizers. The method is applicable to all nitrogenous fertilizers including compound fertilizers, in which nitrogen is found exclusively either in the form of ammonium salts or ammonium salts together with nitrates.

ISO 25475:2016 is not applicable to fertilizers containing urea, cyanamide or other organic nitrogenous compounds.