NPK

NPK refers to the three primary macronutrients required by plants in the largest quantities: Nitrogen (N), Phosphorus (P), and Potassium (K). The NPK ratio displayed on fertiliser labels shows the percentage by weight of each nutrient in the product.

Nitrogen (N) Drives vegetative growth. Essential for chlorophyll and amino acid production. High nitrogen is needed during the vegetative stage; reduced during flowering.

Phosphorus (P) Critical for root development, energy transfer (ATP), and flower/fruit production. Higher phosphorus is typically used during flowering and pre-bloom phases.

Potassium (K) Regulates stomatal function, water uptake, photosynthesis, and disease resistance. Important throughout all growth stages, particularly during flowering for sugar transport and fruit quality.

Reading NPK labels: A fertiliser labelled "10-5-20" contains 10% nitrogen, 5% phosphorus (as P₂O₅), and 20% potassium (as K₂O). The phosphorus and potassium values are expressed as oxides by convention, not as elemental concentrations.

Beyond NPK, plants also require calcium (Ca), magnesium (Mg), sulphur (S), and a range of micronutrients (iron, manganese, zinc, copper, boron, molybdenum). A complete nutrient programme addresses all these elements.