Diammonium Phosphate (DAP) is one of the most widely used high-analysis phosphatic fertilizers, supplying both nitrogen (N) and phosphorus (P) in readily plant-available forms. It is produced by reacting phosphoric acid with ammonia and is valued for its high nutrient concentration, rapid crop response, and wide agronomic adaptability.
Product Identification
| Parameter | Specification |
|---|---|
| Chemical Formula | (NH₄)₂HPO₄ |
| Fertilizer Grade | 18-46-0 (N-P₂O₅-K₂O) |
| Category | Fully water-soluble phosphatic fertilizer |
| Nitrogen Form | Ammoniacal (NH₄⁺) |
| Phosphorus Form | Orthophosphate (HPO₄²⁻) |
| Granule pH | Slightly alkaline (≈7.5–8.0) |
Chemical Nature
DAP is a chemically processed, ammoniated phosphate formed by neutralizing phosphoric acid with ammonia. It supplies dual nutrients and creates a localized alkaline zone near the granule, improving early phosphorus availability and root development.
Strengthening & Agglomeration Mechanism
DAP granules gain mechanical integrity through:
✔ Chemical bonding during ammoniation
✔ Controlled crystallization of ammonium phosphate salts
✔ Thermal curing during granulation and drying
✔ Surface hardening in rotary dryers
📌 No metallurgical strengthening applies (non-metallic compound)
Metallurgical & Thermal Behavior
Thermal Decomposition:
Begins above ~155–170 °C
Releases ammonia (NH₃) and water vapor
Leaves polyphosphate residues
Compatibility:
Non-corrosive under dry conditions
Corrosive to steel when moisture and ammonia coexist
Key Agronomic Characteristics
✔ High phosphorus concentration for efficient transport
✔ Dual nutrient supply (N + P)
✔ Low fixation compared to natural phosphates
✔ Localized pH rise enhances early root growth
✔ Rapid nutrient availability
Refining & Processing
Manufactured through controlled ammoniation and granulation:
✔ Wet-process phosphoric acid production
✔ Ammoniation with anhydrous ammonia
✔ Slurry formation and granulation
✔ Drying, screening, and anti-caking coating
Critical Process Controls:
NH₃ : H₃PO₄ ratio
Granule moisture content
Drying temperature
Particle size distribution
Available Forms
Granular DAP (most common)
Powdered DAP (industrial use)
Technical-grade DAP
NPK fertilizer blends
Industrial Applications
Fire-retardant formulations
Yeast nutrient (food & fermentation)
Flame-proofing textiles
Buffer solutions
Water treatment chemicals
Advantages of DAP
Agronomic:
✔ High nutrient concentration
✔ Fast phosphorus response
✔ Promotes early crop vigor
✔ Improves yield potential
Logistical:
✔ Excellent storage stability
✔ Low dust generation
✔ Easy blending with other fertilizers
✔ Minimal nutrient loss
Limitations & Considerations
Not ideal for alkaline or calcareous soils
Excess use may cause phosphorus buildup
Avoid long-term storage with urea
Moisture control required to prevent caking
Comparison with Other Phosphatic Fertilizers
| Fertilizer | P₂O₅ % | Solubility | Nitrogen |
|---|---|---|---|
| DAP | 46% | Fully soluble | 18% |
| MAP | 52% | Fully soluble | 11% |
| SSP | 16% | Partially soluble | Nil |
| Rock Phosphate | 28–32% | Insoluble | Nil |
Why Choose DAP?
✔ Maximum phosphorus per ton
✔ Fast crop response
✔ Universal compatibility
✔ Proven global fertilizer standard
✔ Ideal for intensive agriculture
Storage & Handling Guidelines
Store in dry, covered warehouses
Avoid moisture exposure
Use plastic-lined or epoxy-coated containers for bulk storage
Follow FIFO (First-In–First-Out) inventory practice