Powdery monoammonium phosphate at 58 % total nutrient sits one tier above the 55 % material. The compound is the same; the difference is how much of each tonne is nutrient and how much is process residue from the phosphate rock. For a compound fertilizer producer this is not a cosmetic difference — every point of total nutrient displaces a point of inert material that must still be paid for, freighted, conveyed, granulated, dried and screened. The tier is chosen on a delivered-cost-per-unit-of-P₂O₅ basis, not on nominal price per tonne.
Substance identity
| Field | Value |
|---|---|
| Active compound | Monoammonium phosphate, NH₄H₂PO₄ |
| CAS | 7722-76-1 |
| PubChem CID | 24402 |
| Molar mass | 115.03 g/mol |
| Grade basis | 58 % = N + P₂O₅ combined |
Specification
Typical commercial range — confirm on certificate of analysis:
| Parameter | Typical |
|---|---|
| Total nutrient (N + P₂O₅) | ≥ 58 % |
| Nitrogen (N), ammoniacal | ≈ 10 – 11 % |
| P₂O₅, total | ≈ 47 – 48 % |
| Moisture | ≤ 2.0 – 2.5 % |
| Physical form | free-flowing powder |
| Appearance | grey to light brown |
| Water-insoluble matter | lower than the 55 % tier; declare on CoA |
Properties
The salt itself is unchanged: NH₄H₂PO₄, mildly acidic in solution, non-hygroscopic relative to nitrogen fertilizers, decomposing above roughly 190 °C with ammonia release.
- Nutrient density economics. Moving from 55 % to 58 % total nutrient is a 5.5 % relative increase in nutrient per tonne handled. On long ocean and inland legs this is usually where the tier decision is actually made.
- Reduced inert throughput. Less non-nutrient material per tonne means less mass through the granulation circuit for the same finished analysis, which affects dryer duty and screening load.
- Impurity profile still wet-process. A higher grade means a lower proportion of inerts, not the absence of them. Iron, aluminium and fluoride species remain present, and water-insoluble content, while lower, is not negligible.
- Powder handling characteristics are as for the 55 % tier: high surface area, dust generation, and a tendency to consolidate under load.
Applications
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NPK compound fertilizer granulation where the target finished analysis is high enough that a lower-grade phosphate feed would make the formulation impossible to close. This is the practical reason to specify 58 % over 55 %: at high finished P₂O₅ targets, the diluent in a low-grade feed leaves no room in the formula.
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Powder blending for high-analysis blended products.
- Buyer-side reprocessing into granular or specialty phosphates.
- Not appropriate for fertigation, foliar application or hydroponics — see the note below.
Handling and storage
As for all wet-process MAP powder: dry covered storage, sealed packaging, dust extraction at transfer points, eye and respiratory protection when handling open material, stock rotation, and stack heights limited to prevent set. Segregate from lime and other alkaline materials, which liberate ammonia on contact and revert soluble phosphate. Keep away from heat.
Notes
-
58 % is total N + P₂O₅ — approximately 10–11 % N and 47–48 % P₂O₅, not 58 % P₂O₅.
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The specification worth comparing between tiers is water-insoluble matter and free acid, not total nutrient alone; two 58 % powders can behave very differently in a granulator.
- Still a wet-process powder. Applications requiring clear solutions need purified technical-grade MAP.