UAN (Urea Ammonium Nitrate Solution) is a liquid nitrogen fertilizer produced by dissolving urea and ammonium nitrate in water. It typically contains 28–32% total nitrogen and supplies nitrogen in three plant-available forms, enabling both immediate and sustained nutrient uptake. UAN is widely used in modern agriculture due to its uniform distribution, ease of application, and compatibility with precision farming systems.
Nitrogen Composition in UAN
UAN supplies nitrogen in three complementary forms:
| Nitrogen Form | Typical Share |
|---|---|
| Urea Nitrogen (NH₂–N) | ~50% |
| Ammoniacal Nitrogen (NH₄⁺–N) | ~25% |
| Nitrate Nitrogen (NO₃⁻–N) | ~25% |
✔ Balanced immediate and sustained nitrogen supply
✔ Fully water-soluble system
Common Grades
UAN-28 (28% N)
UAN-30 (30% N)
UAN-32 (32% N)
Key Physical Properties
| Property | Typical Value |
|---|---|
| Physical State | Clear to slightly yellow liquid |
| Density (UAN-32 @ 20°C) | ~1.32 g/cm³ |
| Viscosity | Low–Moderate |
| Freezing Point | −2 to −18 °C (grade-dependent) |
| Boiling Point | >100 °C (aqueous) |
| Solubility | Completely miscible in water |
| pH | ~6.5–7.5 |
| Hygroscopicity | Not applicable (liquid) |
📌 Density increases with nitrogen concentration
📌 Freezing point is a key logistical consideration
Mechanical Properties
| Property | Behavior |
|---|---|
| Pumpability | Excellent |
| Flowability | Very High |
| Vapor Pressure | Low |
| Cavitation Risk | Low |
| Corrosivity | Mild (carbon steel compatible) |
| Abrasion | None |
✔ Ideal for automated systems
✔ Minimal mechanical degradation
Refining & Processing
UAN is manufactured by preparing aqueous solutions of urea and ammonium nitrate, followed by controlled blending, cooling, filtration, and stabilization.
📌 Integrated with urea and AN plants
📌 No solidification required
📌 Lower energy finishing than granular fertilizers
Available Forms
UAN-28
UAN-30
UAN-32
UAN with urease inhibitors
UAN with nitrification inhibitors
Micronutrient-enriched UAN
Herbicide-compatible UAN blends
Applications
Agriculture: Top dressing, fertigation, foliar feeding (diluted), side-dressing maize, wheat, barley, sugarcane
Precision Farming: Variable-rate application, GPS-controlled sprayers
Industrial & Environmental: Wastewater treatment, regulated chemical uses
Advantages
✔ Uniform nitrogen distribution
✔ Faster crop response
✔ Reduced labor and application cost
✔ Compatible with modern equipment
✔ Flexible timing and application methods
✔ Lower volatilization than surface-applied urea
Limitations & Considerations
Freezing risk in cold climates
Requires liquid handling infrastructure
Corrosive to copper alloys
Higher transport cost due to water content
Leaf burn risk if misapplied