NPK Fertiliser

Summary: NPK fertilisers supply Nitrogen (N), Phosphorus (P), and Potassium (K) to plants. Nitrogen promotes leaf growth; phosphorus supports root development; potassium aids enzyme function and disease resistance. Tags: igcse chemistry fertiliser haber keyword Created: 2026-07-14 Last Updated: 2026-07-14

NPK fertilisers are formulated chemical compounds or blends that supply the three primary elements essential for healthy plant growth: nitrogen (N), phosphorus (P), and potassium (K, from the Latin kalium), with the NPK ratio printed on the packaging (e.g., 15-15-15) indicating the percentage by mass of each element. Each element serves a distinct physiological role — nitrogen is a constituent of proteins and chlorophyll and promotes leafy green growth, phosphorus is vital for ATP synthesis, root development, and cell membranes, and potassium regulates enzyme activity, water balance, and disease resistance. The nitrogen component is typically sourced from ammonia produced via the Haber process, which is reacted with acids to yield ammonium salts: NH₃ + HNO₃ gives ammonium nitrate (NH₄NO₃), while 2NH₃ + H₂SO₄ gives ammonium sulfate ((NH₄)₂SO₄), both of which are widely used nitrogenous fertilisers. Phosphate fertilisers are manufactured by treating phosphate rock (Ca₃(PO₄)₂) with sulfuric acid to produce superphosphate, a soluble form plants can absorb. A critically examined environmental consequence of excessive fertiliser application is eutrophication — nutrient runoff into water bodies triggers explosive algal growth (algal blooms), which blocks sunlight, kills submerged plants, and leads to oxygen depletion when bacteria decompose the dead organic matter, ultimately suffocating fish and other aquatic life — and this process is a recurring topic in IGCSE exam questions on environmental chemistry.

Key term — IGCSE Chemistry (0620/0971) glossary.