NPK fertilisers
- Fertilisers mainly consist of nitrogen compounds (ammonium salts and nitrates), mixed with other nutrients such as phosphorus and potassium compounds.
- They replenish nutrients that are depleted from the soil by repeated harvest.
  - Nitrogen is used for leaf growth.
  - Phosphorus is used for development of roots, flowers, seeds, and fruits.
  - Potassium is used for strong stem growth, movement of water in plants, and promotion of flowering and fruiting.
- Most fertilisers that contain these 3 compounds are called NPK fertilisers. NPK corresponds to the chemical symbol of nitrogen, phosphorus and potassium respectively.
Ammonia in fertilisers
- Ammonia is the source of more than 95% of the chemical nitrogen fertilisers currently produced in the world.
- It may be used directly as a fertiliser, or converted to ammonium salts, nitrates, or urea.
- Ammonium nitrate is one such ammonium salt commonly used as a fertiliser. It can be used as-is, in mixtures with calcium carbonate, or in compound fertilisers including nitrophosphates.

10.03 - Fertilisers

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