NPK Fertilizer Reiknivél (Percent to Application Rate with Blending)
Calculate the fertilizer amount needed to hit target N-P-K nutrient rates from vara grades such as 10-10-10.
Supports blended fertilizers, loss rate, unit conversion, optional cost estimates, and adjustment suggestions when nutrients are short.
How to use
- Set the unit, P and K basis, and loss rate, then enter target N, P, and K nutrient rates.
- Add one or more fertilizers and enter the grade, and optionally price and max application rate.
- Choose a calculation mode and yfirferð shortages, excess, and adjustment suggestions.
Inntaks
- Target nutrient rates: enter N, P, and K in the same unit kerfi.
- Grade inntak: use a 10-10-10 style entry or separate N/P/K sviðs.
- Blending: add rows to combine multiple fertilizers.
- Loss rate: adjust required application for expected nutrient loss.
- Cost: when prices are entered, the verkfæri also estimates total cost.
How to read the úttak
- The summary shows immediately whether the target is met, short, or excessive.
- The fertilizer list shows how much of each vara to apply.
- The nutrient tafla bera samans target, applied, effective, and delta values.
- When nutrients are short, the adjustment panel suggests the next step.
Quick examples
10-10-10 for 60-60-60
Unit kg/ha, P/K basis set to elemental P and K, loss rate 0%, target N=60, P=60, K=60, one fertilizer row with 10-10-10
Required fertilizer rate 600.0 kg/ha, target met, no shortage
Urea + phosphate + potash with no shortage
Unit kg/ha, P/K basis set to P2O5 and K2O, loss rate 0%, target N=60, P2O5=60, K2O=60, plus rows for urea 46-0-0, phosphate 0-20-0, and potash 0-0-60
Urea 130.4 kg/ha, phosphate 300.0 kg/ha, potash 100.0 kg/ha, target met
How the calculation works
- Nutrient fraction f = nutrient percent / 100
- Single-fertilizer amount A = target rate / ((1 - loss rate) x nutrient fraction)
- For blends, the verkfæri searches for a combination that satisfies the no-shortage or priority-match rule while minimizing total cost or total application rate.
Frequently Asked Questions
I want to combine two or more fertilizers.
Add two or more fertilizers and use the "No shortage, lowest total cost" mode. The verkfæri finds a blend that does not fall short. If any price is missing, it minimizes total application rate instead.
My units are different.
Use the unit toggle to switch between kg/ha and lb/acre. Inntaks and niðurstaðas stay in the selected unit kerfi.
My fertilizer label uses P2O5 and K2O.
Switch between elemental P/K and the common P2O5/K2O basis. Internally the verkfæri normalizes everything to elemental P and K.
What if nutrients are still short?
The verkfæri highlights shortages in red, explains the likely cause, such as no source for that nutrient or a max-rate limit, and shows an adjustment suggestion.
Important notes
- This verkfæri performs calculation only. Follow soil analysis, local fertilizer standards, and crop recommendations when making a fertilizer áætlun.
- Excess fertilization can increase environmental load or harm crop growth. Check local rules and svið conditions.
- The loss rate is a simplified model that applies the same percentage to N, P, and K. Actual behavior can differ by nutrient.