Agronomic Nitrogen Efficiency Calculator
Enter nitrogen-treated yield, zero-N control yield, and N rate to compute the Agronomic Efficiency of N: AEN = (Yn − Y0) ÷ F, i.e. how much extra yield per kg of N.
Input Data
Results
At a glance:Enter nitrogen-treated yield, zero-N control yield, and N rate to compute the Agronomic Efficiency of N: AEN = (Yn − Y0) ÷ F, i.e. how much extra yield per kg of N.
Formula
AEN = (Yn − Y0) ÷ F, where Yn = yield with N, Y0 = zero-N control yield, F = N rate (kg N/ha).
Yield gain = Yn − Y0.
$$AEN = \dfrac{Y_n - Y_0}{F}$$How to Use
- Enter the yield in the N-fertilized plot (Yn) and the zero-N control yield (Y0).
- Enter the pure nitrogen applied (F, kg N/ha).
- The calculator returns AEN and the yield gain from N.
FAQ
How is AEN different from Partial Factor Productivity (PFP)?
PFP = Yn ÷ F uses the total yield of the N plot divided by N rate without subtracting the yield the soil would produce anyway, so it also counts the soil's native N supply and yields a larger number. AEN = (Yn − Y0) ÷ F counts only the extra yield from N, better reflecting the true marginal benefit of fertilizer. AEN is preferred for comparing fertilizer efficacy in research; PFP needs no control and is easier to obtain, so it is common for large regional assessments.
Why is a zero-N control needed?
Soil already supplies considerable nitrogen through organic-matter mineralization, residual N, irrigation water, and atmospheric deposition, so crops have a baseline yield Y0 even with no fertilizer. Without subtracting the control, crediting all N-plot yield to fertilizer severely overestimates N benefit. A control plot identical in every way except no N separates the fertilizer's contribution from the soil's background supply, giving the true AEN.
What AEN is considered good?
There is no absolute threshold; it varies with crop, soil, year, and management. Well-managed cereals often show AEN around 10–30 kg yield/kg N: >25 is high, 15–25 is commonly reasonable, and <10 is low (usually over-application or other limits and large N losses). The point is not a single number but how AEN changes as N rate rises — a clear drop signals approaching or exceeding the economically optimal N rate.
Why does AEN fall as N rate increases?
This is diminishing returns. At low N the crop is very deficient, so a little N brings a large yield gain and AEN is high. As N increases, crop and soil N demand is gradually met, and each additional unit of N buys less yield, so AEN falls. Excess N can even stop increasing or reduce yield via lodging, excessive vegetative growth, and disease. Thus AEN's response to N rate is a key basis for detecting excess and finding the optimal N rate.
Should N rate use fertilizer weight or pure N?
Always use pure N (kg N), not the physical fertilizer weight. N content varies widely: urea ~46% N, ammonium sulfate ~21% N, calcium ammonium nitrate ~15.5% N. Pure N = fertilizer amount × N content, e.g. 100 kg urea = 46 kg N. Substituting fertilizer weight for F underestimates AEN and prevents comparison across trials. Enter the converted kg N/ha in the F field.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.