The three numbers on a fertilizer bag are its NPK ratio: the percentage of nitrogen (N), phosphate (P2O5) and potash (K2O) by weight. A 50 kg bag of 10-26-26 contains 5 kg of nitrogen, 13 kg of phosphate and 13 kg of potash. Reading these numbers is the simplest way to choose the right fertilizer and to compare prices fairly.
What N, P and K do
| Nutrient | Main role | Signs of shortage | Common sources |
|---|---|---|---|
| Nitrogen (N) | Leaf and stem growth, green colour | Pale or yellow older leaves, slow growth | Urea (46-0-0) |
| Phosphorus (P) | Roots, early growth, flowering, seed | Weak roots, delayed flowering, purplish leaves | DAP (18-46-0), SSP |
| Potassium (K) | Strength, water use, fruit and grain quality | Brown leaf edges, weak stems, poor fruit | MOP (0-0-60), SOP |
How to read the numbers
The numbers are always in the order N-P-K.
- 19-19-19: 19% N, 19% P2O5, 19% K2O. Balanced.
- 10-26-26: low nitrogen, high phosphate and potash.
- 46-0-0: nitrogen only. This is urea.
- 0-0-60: potash only. This is MOP.
A useful detail: the middle and last numbers are expressed as P2O5 and K2O, not as pure phosphorus and potassium. That is the industry standard, and it is how soil test recommendations are usually written too.
Nutrients per bag: a quick calculation
Bag weight × percentage ÷ 100 = kg of nutrient
A 50 kg bag of 12-32-16 contains 6 kg N, 16 kg P2O5 and 8 kg K2O, or 30 kg of nutrients in total. Divide the bag price by 30 to get the cost per kg of nutrient, and you can compare any two products fairly.
Common NPK ratios and their uses
| Grade | Profile | Typical use |
|---|---|---|
| 46-0-0 (urea) | Nitrogen only | Top dressing during vegetative growth |
| 18-46-0 (DAP) | Phosphate plus some nitrogen | Basal dose at sowing |
| 12-32-16 | Phosphate-rich | Basal dose for wheat, maize, oilseeds, pulses |
| 10-26-26 | Phosphate and potash-rich | Basal dose for paddy, cotton, groundnut, sugarcane |
| 15-15-15, 19-19-19, 20-20-20 | Balanced | General feeding; water-soluble grades for drip and foliar use |
| 13-0-45 (potassium nitrate) | Potash plus nitrogen | Fruiting stage in vegetables and fruit, often through drip |
| 0-0-60 (MOP) | Potash only | Basal potash for most crops |
See NPK fertilizer and complex fertilizer for the grades available in bulk.
Matching the ratio to the crop and stage
Rice
A phosphate and potash-rich basal dose, such as 10-26-26 or DAP plus MOP, then urea in two or three splits during tillering and panicle initiation.
Wheat
DAP or 12-32-16 at sowing, then urea at crown root initiation and tillering.
Vegetables
A balanced grade at planting, then more potash, for example 13-0-45, during flowering and fruiting.
Fruit crops
Nitrogen in the growth flush, phosphate around root and flower development, and plenty of potash as fruit fills. Bananas are especially hungry for potash.
Sugarcane
High nitrogen and potash demand over a long season. See sugarcane fertilizer.
Basal dose and top dressing
- Basal dose: applied at or before sowing. Usually all the phosphate, most of the potash and part of the nitrogen.
- Top dressing: applied later, mostly nitrogen such as urea, when the crop is growing fast.
Splitting nitrogen reduces losses and matches the crop’s demand. See how to use urea as fertilizer.
Why soil testing matters
Many soils already hold plenty of phosphate after years of DAP use, yet farmers keep adding more out of habit. A soil test shows what is really short, so you buy the right ratio and avoid wasted money. It also shows soil pH and micronutrient problems, such as zinc or boron deficiency, that no NPK ratio will fix.
Buying NPK in bulk
Agromer is the distributor for a major European NPK producer, offering standard grades and custom formulas for importers and distributors. Send us the grade, quantity, packaging and destination.
Frequently asked questions
What does NPK 19-19-19 mean?
It contains 19% nitrogen, 19% phosphate (P2O5) and 19% potash (K2O), so equal amounts of each.
What is the best NPK ratio?
There is no single best ratio. It depends on the crop, its growth stage and your soil test.
What is the difference between 10-26-26 and 12-32-16?
Both are basal grades. 12-32-16 has more phosphate. 10-26-26 has more potash.
Is urea an NPK fertilizer?
Urea is a straight nitrogen fertilizer with a grade of 46-0-0. It supplies only N.
Why are P and K shown as P2O5 and K2O?
It is the long-standing industry convention for labelling phosphate and potash content.
How much nitrogen is in a 50 kg bag of urea?
23 kg, because urea contains 46% nitrogen.