Commodities
Fertilizers: urea, ammonium products, potash and NPK
An introduction to the main fertilizer products, how nutrient content is stated, how they are packed and shipped, and where special rules apply.
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The three main nutrients
Plants need nitrogen, phosphorus and potassium in large amounts. Fertilizer labels express them as N for nitrogen, P2O5 for phosphate and K2O for potash. A product marked 15-15-15 contains 15 percent of each. Straight fertilizers carry mainly one nutrient. Compound products, often called NPK, carry two or three.
Nitrogen fertilizers
Urea
The most traded nitrogen fertilizer, with a nitrogen content of about 46 percent, the highest among common solid products. It is sold in two forms. Prilled urea is made by dropping molten urea down a tower, and granular urea is formed by building up layers in a granulator, giving a harder, larger, more uniform particle that is easier to store and spread. Granular urea often trades at a premium.
Ammonium nitrate and calcium ammonium nitrate
Ammonium nitrate carries around a third nitrogen by weight and is an oxidiser. Because it can be misused, it is controlled in many countries, requires specific storage and may be classed as dangerous goods for shipping. Calcium ammonium nitrate is a blend with a lower risk profile. Always check the licences and the transport classification.
Ammonium sulphate
A nitrogen and sulphur fertilizer, with around a fifth nitrogen and a significant amount of sulphur. Useful where soils lack sulphur.
Phosphate and potash
Phosphate fertilizers such as DAP (diammonium phosphate) and MAP (monoammonium phosphate) provide nitrogen and phosphate together, and TSP (triple superphosphate) is a high-phosphate product. Potash, mainly muriate of potash or MOP, is potassium chloride and is commonly sold on a K2O basis, often around 60 percent. Sulphate of potash is used for chloride-sensitive crops.
NPK compounds
Compound fertilizers are made by granulating or blending raw materials into a specified ratio. Blends are mixed physically and can separate if handled badly, while complex fertilizers have each granule carrying the nutrients. Ask which of the two is being offered, and ask for the nutrient analysis, particle size and moisture.
What to check in a specification
- Nutrient content, stated as a minimum, and the basis of the figure.
- Form: prilled, granular, crystalline, powder or liquid.
- Moisture, which causes caking and weight differences.
- Size range, and the share of dust or fines.
- Biuret in urea, a by-product that is limited because it can harm some crops. Check the maximum accepted by the buyer's market.
- Packing: bags of a defined weight, large bulk bags, or bulk cargo.
Shipping and storage
Fertilizers are hygroscopic: they absorb moisture and cake. Bags and liners, dry holds and quick discharge matter. Bulk cargo needs a clean hold with no residue of other products. Dangerous or controlled products need declarations, correct labelling and a carrier willing to take them. Allow time for permits and port rules.
Pricing and seasons
Fertilizer demand follows planting seasons, so tenders and deliveries cluster at certain times. Prices are quoted per metric ton for a stated basis and often move with energy and crop markets. Government-run tenders and subsidy rules in some importing countries affect timing. Because prices move, a short validity on any offer is normal.
Documents
Expect the bill of lading, commercial invoice, certificate of origin, certificate of analysis and a weight certificate. Some importers require registration of the product, a safety data sheet or a specific import permit. Ask the buyer for the list at the start.
Frequently asked questions
- What is the difference between prilled and granular urea?
- Prills are small, rounded particles formed by cooling droplets, while granules are larger, harder and more uniform. Granular urea handles and spreads better and usually sells at a premium.
- What does 46-0-0 mean?
- It indicates 46 percent nitrogen, no phosphate and no potash, the typical analysis of urea.
- Why is ammonium nitrate regulated?
- It is an oxidising material that can be dangerous if stored or handled incorrectly or misused, so many countries require permits and set transport rules.
- Why does moisture matter in fertilizer?
- Moisture causes caking, dust problems and weight differences, and it can break down some products over time.
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