Fertilisers
Section: 10. Chemistry of the Environment | Syllabus: Cambridge IGCSE Chemistry (0620)
Fertilisers
Ammonium salts and nitrates are used as fertilisers - for example, ammonium nitrate (NH₄NO₃) and ammonium sulfate ((NH₄)₂SO₄). They dissolve readily in water, so the nutrients they supply are quickly available to plant roots.
NPK Fertilisers
NPK fertilisers supply the three elements nitrogen (N), phosphorus (P) and potassium (K), for improved plant growth.
Worked Example
- Question (based on a real exam question): nitrogen and phosphorus are elements contained in NPK fertilisers.
- Name the other element contained in NPK fertilisers. [1]
- State why fertilisers are used. [1]
- One compound found in fertilisers contains the ions NH₄⁺ and NO₃⁻ only. State the name of this compound. [1]
- Answer: (1) potassium; (2) improved plant growth; (3) ammonium nitrate
Nitrates and phosphates washed off fields into rivers cause deoxygenation of water, damaging aquatic life - see Substances in Water from Natural Sources for the details of this harm.
Common Mistakes
- ❌ Forgetting which letter of "NPK" stands for which element
- ✓ N = nitrogen, P = phosphorus, K = potassium (from the Latin kalium) - all three are supplied together to improve plant growth
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