Calcium Ammonium Nitrate (CAN) Fertilizer

CAN (Calcium Ammonium Nitrate) is a widely used nitrogen fertilizer that contains both ammonium nitrate (NH₄NO₃) and calcium carbonate (CaCO₃) or limestone/dolomite.

It is considered a safer alternative to pure ammonium nitrate because the added calcium reduces its explosiveness.

Composition

Component	Percentage (%)
Total Nitrogen (N)	25 – 28 %
– Nitrate nitrogen (NO3-N)	12.5 – 14 % (quick-acting)
– Ammonium nitrogen (NH4-N)	12.5 – 14 % (slow-acting)
Calcium (Ca) as CaO	6 – 10 %
Magnesium (Mg) (in dolomitic grades)	2 – 4 %

Method of Preparation (Industrial Process)

1. Production of Ammonium Nitrate Solution
   Neutralization of nitric acid with ammonia:
   NH₃ + HNO₃ → NH₄NO₃ (exothermic)
2. Addition of Limestone/Dolomite
   Finely ground limestone (CaCO₃) or dolomitic limestone (CaCO₃·MgCO₃) is mixed with the hot, concentrated NH₄NO₃ solution.
3. Granulation
   The slurry is sprayed into a granulation drum or prilling tower where it is dried and formed into uniform granules (2–4 mm).
4. Coating (optional)
   Granules are coated with anti-caking agents to improve storage properties.
5. Cooling & Packaging
   Cooled granules are screened, packed, and stored.

Physical & Chemical Properties

Property	Description
Appearance	White to greyish, free-flowing granules
Solubility	Highly soluble in water
pH (10% solution)	5.5 – 7.0 (nearly neutral)
Hygroscopicity	Less hygroscopic than pure AN
Explosive risk	Very low (calcium reduces sensitivity)
Bulk density	0.9 – 1.1 g/cm³

Advantages (Why Farmers Prefer CAN)

• Dual nitrogen source: fast-acting nitrate + slow-acting ammonium
• Supplies calcium – prevents calcium-related disorders (e.g., blossom-end rot in tomatoes)
• Does not acidify soil (unlike pure ammonium nitrate)
• Safer to store and transport than pure ammonium nitrate
• Suitable for all crops and soils, especially calcareous soils

Main Uses

• Top dressing for cereals, oilseeds, and grasslands
• Side dressing for vegetables and fruit crops
• Broadcast application before sowing
• Fertigation (in some soluble grades)
• Widely used in Europe, Africa, and Middle East

Environmental Impacts of CAN Fertilizer

Positive / Lower-Impact Aspects (compared to pure AN or urea)

• Less soil acidification – Limestone component neutralizes acidity produced during nitrification.
• Supplies calcium and magnesium – improves soil structure and prevents Ca-related plant disorders.
• Lower ammonia volatilization than urea (especially on high-pH soils).
• Reduced explosion risk – safer storage and transport.

Negative Environmental Impacts

• Nitrate leaching: The 50% nitrate-N is immediately available and highly mobile → major contributor to groundwater NO₃⁻ pollution, especially on light soils and during winter.
• N₂O (nitrous oxide) emissions: During nitrification and denitrification of both ammonium and nitrate portions → N₂O is a potent greenhouse gas (265× CO₂ over 100 years).
• Eutrophication: Leached or runoff nitrate causes algal blooms in rivers, lakes, and coastal waters.
• Energy-intensive production: Nitric acid and ammonia production require large amounts of natural gas → high carbon footprint (≈ 3–4 kg CO₂-eq per kg N).
• Ammonia emissions: Minor NH₃ loss possible during spreading, contributing to particulate matter (PM2.5) and indirect N₂O.

Comparison with Other Nitrogen Fertilizers (Environmental Ranking)

Fertilizer	Acidification	NH3 Volatilization	NO3⁻ Leaching Risk	N2O Emissions
Urea	High	Very High	Medium	Medium-High
Ammonium Nitrate (AN)	High	Low	Very High	High
CAN	Low–Neutral	Low	High	High
Ammonium Sulfate	Very High	Low	Medium	Medium
UAN (solution)	Medium	Medium	Very High	High

Best Practices to Minimize Environmental Harm

• Apply in split doses according to crop demand
• Avoid application before heavy rain or on frozen ground
• Incorporate immediately on light soils if possible
• Use nitrification inhibitors (e.g., DMPP, nitrapyrin) in high-risk areas
• Follow local N-max limits and nitrate vulnerable zone (NVZ) regulations