Preparation of a potassium phosphate based composition

A process for manufacturing a solid, particulate fertilizer based on potassium phosphate of the formula K3H3(PO4)2, said process comprising

• i) providing agriculturally acceptable raw material essentially consisting of monopotassium phosphate (KH2PO4, MKP);
• ii) providing agriculturally acceptable raw material essentially consisting of potassium hydroxide (KOH);
• iii) adding water to said MPK in an amount of from 20 to 100 wt%, based on dry weight of the MKP;
• iv) adding said raw KOH to said MKP and water from step iii) in an amount of from about 17 wt% to about 23 wt%, based on dry weights of KOH and MKP;
• v) heating the mixture of step iv) under movement at temperatures of up to about 140° C., comprising vacuum, until a homogeneous material containing from about 0.2 wt% to about 8 wt% water is obtained;
• and
• vi) cooling the mixture of step v) down to ambient temperature;
• thereby obtaining the particulate fertilizer based on potassium phosphate, freely flowing and without tendency to cake.