The experiments were carried out in a thermostated cylindrical reactor equipped with a helical stirrer. The temperature in the thermostat was 65С. The weight ratio of WPA: WDC ranged from 100: 10 to 100: 30. Phosphate raw materials were introduced into the reactor with a sample of WPA. The duration of the decomposition process from the moment the feedstock is loaded is 45 minutes. After the end of the decomposition process, the pulp was ammoniated to pH = 3.8. The granulation of ammonized slurries was carried out during drying at 85-90C by the balling method. Then the product was cooled and analyzed for the content of nitrogen, various forms of phosphorus and calcium. Determination of all forms of P2O5 (total (t.), acceptable by citric acid (ac.c.a.), water soluble (w.s.) was carried out by the differential method widely used in the analysis of phosphate ores on a KFK-3 instrument ( = 440 nm) in the form of a phosphorus vanadium -molybdenum complex. The assimilable form of P2O5 was determined by its solubility both in 2% citric acid and in a 0.2 M solution of Trilon B. The determination of CaO content was carried out by a volumetric complexometric method: titration with 0.05 n Trilon B solution in the presence of the fluorexon indicator. The acceptable by citric acid form of CaO -only 2% citric acid.