Diammonium phosphate supplied at a declared total nutrient content of 57 % is the lower of the two standard commercial DAP tiers. Nitrogen plus P₂O₅ together reach 57 percentage points, most commonly split around 15 % N and 42 % P₂O₅. The chemistry, the alkaline granule reaction and the seed-placement caution are all identical to standard DAP; what differs is nutrient density per tonne, and therefore the freight, handling and formulation arithmetic that surrounds it.
Substance identity
| Field | Value |
|---|---|
| Active compound | Diammonium hydrogen phosphate, (NH₄)₂HPO₄ |
| CAS | 7783-28-0 |
| PubChem CID | 24540 |
| Molar mass | 132.06 g/mol |
| Grade basis | 57 % = N + P₂O₅ combined |
Specification
Typical commercial range — confirm on certificate of analysis:
| Parameter | Typical |
|---|---|
| Total nutrient (N + P₂O₅) | ≥ 57 % |
| Nitrogen (N), ammoniacal | ≈ 14 – 16 % |
| P₂O₅, total | ≈ 41 – 43 % |
| Moisture | ≤ 2.0 – 2.5 % |
| Particle size | ≥ 90 % within 2 – 4 mm |
| Bulk density | ≈ 0.9 – 1.0 t/m³ |
| Appearance | grey, brown or off-white granules |
Properties
Chemically this is diammonium phosphate and it behaves as such: alkaline solution reaction near pH 8, free ammonia generated at the dissolving granule, thermal decomposition with ammonia loss, critical relative humidity around 82.5 % at 30 °C.
- Lower nutrient density. Delivering a given quantity of P₂O₅ requires roughly 10 % more tonnage than with the 64 % tier. On short supply legs this is often irrelevant; on long ones it dominates.
- Higher inert fraction. The balance is moisture and rock-derived impurity, which also means proportionally more material through spreaders, conveyors and granulation circuits.
- N:P₂O₅ ratio is different, not just diluted. At roughly [CAS?] the ratio is about 1 : 2.8, against 1 : 2.6 for [CAS?]. When substituting one tier for another in an existing blend recipe, both legs must be recalculated — not just the phosphate leg.
Applications
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Basal N + P application on cereals, maize and other field crops, drilled or broadcast and incorporated.
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Regional supply where this tier is the locally established standard and the distribution chain, bagging and blending recipes are already built around it.
- Blending where a lower-analysis phosphate leg is acceptable and the blend is closed with urea or ammonium sulfate.
- Placement caution carries over in full. The free-ammonia hazard from the alkaline granule reaction is a property of the compound, not of the grade. A lower total nutrient figure does not make this product safer for seed contact. Side-band or separate from the seed row; use MAP where seed-placed phosphate is genuinely required.
Handling and storage
Dry, covered, ventilated storage on pallets; sealed packaging; stock rotation, because DAP loses ammonia slowly in warm humid storage. Segregate absolutely from lime, basic slag and other alkaline materials. Keep away from strong acids and from heat. Ventilate bulk storage. Limit handling transfers to reduce fines, which degrade spread pattern.
Notes
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57 % is total N + P₂O₅, approximately 14–16 % N and 41–43 % P₂O₅.
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When comparing this tier against 64 % DAP, the meaningful comparison is delivered cost per unit of P₂O₅ and per unit of N, evaluated together, not price per tonne.
- Request water-soluble P₂O₅ as a percentage of total, not total P₂O₅ alone.