Diammonium phosphate (18-46-0) (DAP) and monoammonium phosphate (11-52-0) (MAP) are the two most common phosphorus (P) fertilizers in the US corn-belt. These granular fertilizers are excellent P sources because they are highly water-soluble, contain a high P concentration, and are easy to handle and store (Fixen, 1990). In addition, they represent a relatively low-cost source of supplemental N.
Soil Science Extension
University of Wisconsin Madison