What do the numbers on an NPK fertilizer mean?
N-P-K stands for nitrogen, phosphorus, and potassium — the three primary macronutrients every fertilizer label declares. The three numbers, always in that order, state the guaranteed percentage of each nutrient by weight. A product labelled 17-17-17 guarantees 17% nitrogen, 17% phosphorus (as P₂O₅), and 17% potassium (as K₂O).
Balanced versus targeted ratios
An equal ratio like 17-17-17 delivers balanced nutrition across the crop cycle, useful as a general maintenance feed. Most professional programmes instead shift the ratio to match the crop's stage: phosphorus-led blends support rooting and early establishment, while potassium-led blends support ripening and fruit quality when potassium demand peaks late in the cycle.
Reading the ratio for the stage
| Ratio type | Example grade | Best for |
|---|---|---|
| Phosphorus-led | 7-20-7 | Rooting, early establishment, flower induction |
| Balanced | 17-17-17 | Steady, even growth across the crop cycle |
| Potassium-led | 5-5-33 | Ripening, finishing, fruit quality |
| Nitrogen-led | 21-0-7, 28-16-4 | Vegetative growth phases, canopy development |
Las Raíces' Raiz NPK line is built around exactly this logic — a family of liquid NPK grades, each formulated with chelated micronutrients, so growers can match the ratio to the stage rather than using one blend for the whole cycle.
One number isn't the whole story
The N-P-K ratio is the headline, but the guaranteed analysis also lists the chelated micronutrients, pH, and density that determine how a product behaves in your tank and soil — worth checking before you scale up an application.