Every fertilizer bag carries three numbers — 46-0-0, 18-46-0, 0-0-60. They're percentages of the three nutrients crops need most, and reading them correctly is the difference between a precise dose and wasted money.
What N, P and K do
- N — Nitrogen: drives leafy, green growth. Deficiency shows as pale, yellowing older leaves. Excess gives lush foliage but poor grain and lodging.
- P — Phosphorus (as P₂O₅): roots, flowering and grain fill. Critical early — it's why DAP goes in at sowing.
- K — Potassium (as K₂O): water regulation, disease resistance and grain quality.
Reading the three numbers
The numbers are percent by weight. A 50 kg bag of urea (46-0-0) contains 23 kg of actual nitrogen. A 50 kg bag of DAP (18-46-0) contains 9 kg N and 23 kg P₂O₅. MOP (0-0-60) is 60% K₂O. So a recommendation like "48 kg N per acre" is not 48 kg of urea — it's about 104 kg of urea (48 ÷ 0.46).
Enter your N-P-K target and area — get the exact kg of urea, DAP and MOP.
Open Fertilizer CalculatorWhy DAP goes first in the math
DAP supplies both P and N, so the correct sequence is: size the DAP to hit your phosphorus target, note the nitrogen it already contributes, then top up the remaining N with urea, and cover K with MOP. Doing it in the wrong order over-applies nitrogen — the most common on-farm dosing error. Our calculator follows this sequence automatically and includes crop presets for wheat, rice, maize, cotton and more.
Practical dosing rules
- Soil-test when you can. Recommendations assume average soil; a test replaces guesswork with your field's actual numbers.
- Split nitrogen applications. N leaches easily — half at sowing and the rest in one or two top dressings loses far less than a single dose.
- Don't skip K because deficiency is invisible early. Potassium shortfalls show up late, in weak stems and shrivelled grain, when it's too late to fix.
- Track what you spend. Fertilizer is usually the second-biggest input cost — log it in the Farm Expense Tracker and compare against your crop profit projection.
For the planning side — seed rates, yield estimates and profitability — see our crop planning guide.