Inorganic fertilizers - Determination of extracted phosphorus P2O5

This document specifies a method for the determination of phosphorus in fertilizer extracts. The method is applicable to all extracts of fertilizers for the determination of the different forms of phosphorus as phosphorus soluble in mineral acids, water-soluble phosphorus, phosphorus soluble in solutions of neutral ammonium citrate, phosphorus soluble in 2 % citric acid and phosphorus soluble in a mass fraction of 2 % formic acid. The method has only been validated on inorganic fertilizers but can be applicable to all extracted phosphorous if proper extraction methods are used.