Description
Monoammonium phosphate (MAP) is a widely used source of phosphorus (P) and nitrogen (N).* It’s made of two constituents common in the fertilizer industry and contains the most phosphorus of any common solid fertilizer.
Production
MAP’s manufacturing process is relatively simple. While there are multiple methods, two common ways include:
A one-to-one ratio of ammonia (NH₃) and phosphoric acid (H₃PO₄) is reacted and the resulting slurry of MAP is solidified in a granulator
Introducing the two starting materials in a pipe-cross reactor, where the reaction generates heat to evaporate water and solidify MAP
An advantage of manufactured MAP is that lower-quality H₃PO₄ can be used compared with other P fertilizers often requiring a more pure grade of acid. The phosphorus pentoxide (P₂O₅) equivalent content of MAP varies from 48 to 61 percent, depending on the amount of impurity in the acid. The most common fertilizer composition is 11-52-0.
Chemical properties
- Chemical formula: NH₄H₂PO₄
- P₂O₅ range: 48-61%
- N range: 10-12%
- Water solubility (20 degrees): 370 g/L
- Solution pH: 4 to 4.5
Agricultural use
MAP has been an important granular fertilizer for many years. It’s water-soluble and dissolves rapidly in adequately moist soil. Upon dissolution, the two basic components of the fertilizer separate again to release ammonium (NH₄⁺) and phosphate (H₂PO₄⁻), both of which plants rely on for healthy, sustained growth.
