Ammoniacal Nitrogen Fertilizers supply nitrogen to plants in ammonium (NH₄⁺) form. This positively charged nitrogen binds to soil colloids, reducing leaching losses and enabling gradual nitrogen availability. These fertilizers are especially effective in flooded, acidic, and heavy soils, making them essential for rice cultivation and controlled nitrogen management.
Major Ammoniacal Nitrogen Fertilizer Grades
| Product | Formula | Key Nutrients | Notes |
|---|---|---|---|
| Ammonium Sulfate (AS) | (NH₄)₂SO₄ | 21% N, 24% S | Strongly acid-forming |
| Ammonium Chloride (AC) | NH₄Cl | 26% N, 66% Cl | Acidic reaction |
| Ammonium Phosphate | MAP / DAP | 11–18% N + P | Dual nutrient (N + P) |
| Ammonium Thiosulfate (ATS) | — | 12% N, 26% S | Liquid, inhibitor-compatible |
| Anhydrous Ammonia | NH₃ | 82% N | Converts to NH₄⁺ in soil |
Key Characteristics
✔ Positively charged – binds to soil particles
✔ Lower leaching risk than nitrate nitrogen
✔ Gradual nitrogen release
✔ Improves nitrogen use efficiency
✔ Enhances phosphorus availability
✔ Acidifies soil over time
Strengthening & Metallurgical Behavior
Ammoniacal nitrogen compounds have no structural strengthening role, but they play important chemical and thermal roles:
✔ Used in metal surface treatments
✔ Provide reducing atmospheres at high temperature
✔ Serve as precursors for nitriding processes
✔ Act as flux components in certain metallurgical salts
📌 Primarily chemical-reactive behavior, not mechanical
Refining & Processing
Ammoniacal fertilizers are produced by reacting ammonia with mineral acids, followed by crystallization, granulation, or solution blending.
✔ Granulation or crystallization for solids
✔ Liquid ammonium solutions for fertigation
✔ Coatings to prevent caking
✔ Often blended with nitrification inhibitors
📌 Processing controlled by ammonia purity
📌 Energy-intensive and petrochemical-dependent
Available Forms
Granular fertilizers
Crystalline powders
Liquid ammonium solutions
Gas (anhydrous ammonia)
Blended NPK fertilizers
Water-soluble grades
Applications
Agriculture: Rice and flooded crops, acidic and neutral soils, slow-release nitrogen systems, sulfur- or phosphorus-deficient soils
Horticulture: Controlled vegetative growth, root development, nursery production
Industrial: Metal finishing, chemical synthesis, water treatment, pH adjustment
Advantages
✔ Reduced nitrogen leaching losses
✔ Higher nitrogen retention in soil
✔ Suitable for flooded and heavy soils
✔ Improves nutrient uptake efficiency
✔ Lower cost than nitrate fertilizers
✔ Long-lasting nitrogen availability
Comparison: Ammoniacal vs Nitrate Nitrogen
| Feature | Ammoniacal (NH₄⁺) | Nitrate (NO₃⁻) |
|---|---|---|
| Soil Retention | High | Low |
| Leaching | Low | High |
| Plant Uptake | Indirect | Direct |
| Soil pH Effect | Acidifying | Neutral |
| Speed of Action | Moderate | Fast |
Limitations
Soil acidification over time
Possible ammonia volatilization if not incorporated
Requires microbial nitrification
Not ideal for very cold soils
Chloride sensitivity (NH₄Cl)