Agriculture
Fertilizer Input Rate Calculator
Balance nitrogen, phosphate, and potash requirements against nutrient credits and product analyses using a transparent DAP, urea, and potash blend.
Nutrient material balance
Meet N, P₂O₅, and K₂O targets without double-counting nitrogen supplied by DAP
The sequence assigns phosphate with DAP, credits its nitrogen, then supplies remaining nitrogen with urea and potash with muriate of potash.Blend composition
Product mass and delivered nutrient balance
Product blocks show carrier mass; nutrient rails confirm delivered N, P₂O₅, and K₂O after credits.Detailed calculation process
Assign multi-nutrient products first, then close the remaining nutrient gaps
General symbolic formulas
Nreq = max(N - CN,0)/ePreq = max(P - CP,0)DAP = Preq/aDPNDAP = DAP × aDNUrea = max(Nreq-NDAP,0)/aUMOP = max(K-CK,0)/aKCredits are removed before product rates are calculated. DAP is sized to phosphate need, and its nitrogen contribution reduces the urea requirement.
Symbols and units
Worked substitution with current inputs
Nutrient and product ledger
| Product | Rate kg/ha | N supplied | P₂O₅ supplied | K₂O supplied | Field total |
|---|
Use steps
- Set targets from crop plan and soil test.
- Enter only available nutrient credits.
- Replace analyses with actual product labels.
Examples
Manure credit: raise available N only by the first-year available amount.
Different phosphate: this sequence must be recalculated for a product other than DAP.
Limitations
This arithmetic does not recommend nutrient targets or address placement, timing, salts, micronutrients, pH, regulations, blend compatibility, or maximum safe seed-row rates.
Fertilizer-rate FAQ
Why divide N by efficiency?
The applied plant-available requirement must be higher when only part of applied N is recovered.
Why is DAP calculated before urea?
DAP supplies both phosphate and nitrogen, so its N must be credited before closing the N balance.
Are P and K elemental?
No. Inputs and labels use the common fertilizer conventions P₂O₅ and K₂O.