Transformation of copper compounds in the conditions of obtaining complex fertilizers

The results of studies on the behavior of the copper trace element in the production of complex nitrogen-phosphorus fertilizers – ammophos and nitroammophos are presented. It is shown that, when copper oxide and sulfate are introduced into solutions of phosphoric and mixtures of nitric and phosphoric acids, copper appears in the form of dihydrophosphate. Copper hydrophosphate precipitates in the ph range of 1.6–2, and at a ph above 6 copper ammonium phosphate is formed. During ammonization of a mixture of nitric and phosphoric acids containing copper, copper hydrophosphate is formed in the ph range of 1.2–4.1, and at a ph above 5.2, copper ammonium phosphate precipitates. Under the conditions for obtaining copper-containing ammophos, copper is in the form of a mixture of hydrophosphate and copper ammonium phosphate. Under the conditions for obtaining nitroammophos, copper is mainly in the form of hydrophosphate with a lethal content of copper ammonium phosphate. Both in ammophos and in nitroammophos, copper is in a form assimilated by plants, which indicates the possibility of introducing the microelement copper at various stages of obtaining complex phosphorus-containing fertilizers.