NPK

Key Stage 4

Meaning

NPK is a mixture of fertilising compounds used in agriculture.

About NPK

NPK stands for Nitrogen (N), Phosphorous (P), Potassium (K).

NPK is generally made by reacting Ammonia with Nitric Acid, reacting Ammonia with Phosphoric Acid and combining these in a mixture with Potassium Chloride which is mined from the ground.

Ammonia + Nitric Acid → Ammonium Nitrate

<chem>NH3 + HNO3 -> NH4NO3</chem>

Ammonia + Phosphoric Acid → Ammonium Phosphate

<chem>3NH3 + H3PO4 -> (NH4)3PO4</chem>

NPK can also include other minerals such as Calcium Phosphate and Calcium Sulphate as plants also need both Calcium and Sulphur.

References

AQA

NPK fertilisers, page 105, GCSE Chemistry; The Revision Guide, CGP, AQA

NPK fertilisers, pages 234-235, GCSE Chemistry; Third Edition, Oxford University Press, AQA

NPK fertilisers, pages 268-9, GCSE Chemistry, Hodder, AQA

NPK fertilisers, pages 304, 305, GCSE Chemistry, CGP, AQA