Method for preparing NPK fertilizer containing potassium phosphate and ammonium phosphate

The invention relates to a method for producing a liquid NPK fertilizer, characterized in that the reactants K2CO3 or KHCO3, NH4HCO3 and H3PO4 are reacted in an aqueous solution to form potassium phosphate and ammonium phosphate, in particular K3PO4 and (NH4) 3PO4, the reaction being carried out in a plurality of steps and comprising at least one exothermic reaction and at least one endothermic reaction, and wherein the reaction temperature is controlled by adjusting the addition amount and the addition rate of the respective reactants in different steps such that the reaction mixture is maintained within the desired temperature range, preferably within the temperature range of 5 DEG C to 50 DEG C, throughout the reaction without any external cooling or heating means to control the reaction temperature. In more specific embodiments, the method according to the invention is characterized in that the at least one exothermic reaction comprises the reaction of K2CO3 with H2O to form KHCO3 and KOH and/or the react