Explain why nitrogen, phosphorus, and potassium are important in fertilisers.

Nitrogen is crucial for plant growth as it is a key component of proteins and chlorophyll. Phosphorus is important for energy transfer and root development, while potassium helps in water regulation and overall plant health.

A strong answer should directly address the approved learning objective to define NPK fertilisers as fertilisers containing compounds of nitrogen, phosphorus and potassium. (Chemistry only). This question belongs to Production and uses of NPK fertilisers within The Haber process and the use of NPK fertilisers, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to phosphorus, and keeps the wording specific to AQA GCSE revision.