The difference between 3 Nitrogen Fertilizers: Ammonium, Nitrate, Amide

Nitrogen fertilizers are categorized by molecular structure into three primary types: ammonium, nitrate, and amide nitrogen forms. High-nitrogen fertilizers include urea (46.7% N), ammonium nitrate (34-35% N), ammonium chloride (25-26% N), ammonium sulfate (21% N), and ammonium bicarbonate (17% N). Understanding their distinct behaviors is critical for optimizing nitrogen use efficiency (NUE).

1. Ammoniacal Nitrogen Fertilizers

Chemical Representatives:

• Ammonium sulfate ((NH₄)₂SO₄)

• Ammonia water (NH₃·H₂O)

• Ammonium bicarbonate (NH₄HCO₃)

• Anhydrous ammonia (NH₃)

• Ammonium chloride (NH₄Cl)

Key Properties:

• Cationic adsorption: NH₄⁺ ions bind to soil colloids and clay interlayers (CEC-dependent)

• Plant uptake pathways:

  • Direct absorption as NH₄⁺

  • Nitrification to NO₃⁻ (mediated by Nitrosomonas and Nitrobacter)

• Volatility risk: High pH (>7.5) triggers NH₃ loss (up to 40% in calcareous soils)

• Antagonism: Excessive application inhibits Ca²⁺/Mg²⁺/K⁺ uptake and causes phytotoxicity at >200 ppm

Agronomic Guidelines:

• Apply in acidic to neutral soils (pH 5.5-7.0)

• Incorporate immediately to minimize volatilization

2. Nitrate Nitrogen Fertilizers

Chemical Representatives:

• Calcium nitrate (Ca(NO₃)₂)

• Sodium nitrate (NaNO₃)

• Ammonium nitrate (NH₄NO₃)

Distinctive Characteristics:

• High solubility: >800 g/L at 20°C

• Anionic mobility: NO₃⁻ not adsorbed by soil colloids → prone to leaching

• Denitrification risk: Anaerobic conditions convert NO₃⁻ to N₂O/NO/N₂ (losses up to 60%)

• Cation synergy: Enhances Ca²⁺/Mg²⁺/K⁺ uptake without antagonism

Management Strategies:

3. Amide Nitrogen Fertilizers (Urea)

Chemical Formula: CO(NH₂)₂
Technical Specifications:

• Highest N content: 46.7% (among solid fertilizers)

• Physiologically neutral: No residual soil acidity/alkalinity

• Biuret hazard: Forms at >140°C during granulation; limits:

  • <0.5% for general use

  • <1% for seed/seedling contact prohibition

Soil Transformation Process:

Conversion rate: 50% in 2 days at 30°C vs. 7 days at 10°C

Application Protocols:

• Timing: Apply 4-8 days before peak N demand

• Methods:

  • Base dressing: Incorporate 10-15 cm deep

  • Top-dressing: Follow with irrigation ≤24h

• Prohibitions:

  • Seed fertilizer (biuret toxicity)

  • Foliar spray >0.5% concentration

Comparative Analysis

Best Practices for Nitrogen Management

1. Inhibitor Technologies:

   • NBPT for urea (reduces NH₃ loss by 50-70%)

   • DMPP or CP for urea(increase utilization by 80%)

   • DCD for nitrates (suppresses denitrification)

2. Precision Application:

   • Soil-test-based variable rate (STVRT)

   • 4R Nutrient Stewardship framework (Right Source, Rate, Time, Place)

3. Environmental Safeguards:

   • Buffer zones near waterways

   • Real-time N-sensors to prevent over-application

“Urea’s high N concentration demands precise management – its agronomic efficiency hinges on synchronizing hydrolysis with crop demand.”
― IFA Advanced Fertilizer Manual, 2025 Edition