Suspension quality and grade from commercial MAP

Abstract

Nine commercially available granular monoammonium phosphate (MAP) products were tested for use in production of suspension fertilizers. The MAP products were dissolved and ammoniated in a 50-pound batch pilot plant to produce 9-27-0, 10-30-0, and 11-33-0 grade suspensions with attapulgite clay used as the suspending agent. Storage properties of the suspension products then were evaluated for up to 12 weeks. Suspensions that were rated unsatisfactory either initially or after a period of storage were primarily nonpourable due to formation of strong phosphate gels formed with the metallic impurities (iron, magnesium, and aluminum). Efforts then were made to correlate level of impurity content of the solid MAP products with the highest satisfactory grade suspension that could be produced and length of satisfactory storage that could be expected.