How is nitrogen uptake calculated from yield?

Crop nitrogen uptake equals harvested dry-matter yield multiplied by the nitrogen concentration of that harvested material. For example, 8 tonnes of wheat grain at 2 percent nitrogen removes 160 kg of nitrogen per hectare in the grain.

What counts as nitrogen supplied?

Total nitrogen supplied includes mineral fertilizer nitrogen, the plant-available nitrogen in any manure or organic amendment applied, and atmospheric deposition. Some definitions also include residual soil mineral nitrogen; this tool lets you add an organic and deposition figure.

What is a good NUE value?

Recovery-based NUE for cereals commonly sits between 40 and 65 percent in well-managed systems. A value below about 40 percent suggests losses through leaching, volatilization, or denitrification and an opportunity to cut rates or split applications. Values near or above 100 percent indicate the crop is mining soil nitrogen.

Why can NUE exceed 100 percent?

If the crop removes more nitrogen than you applied, it is drawing on soil organic-matter mineralization or residual nitrogen. That is unsustainable over time and signals that the soil nitrogen bank is being depleted and needs replenishing.

Should I keep units consistent?

Yes. Keep yield and all nitrogen figures in the same area basis, for example per hectare or per acre, and the same mass unit. The tool works on whatever consistent units you enter because NUE is a ratio.

Nitrogen Use Efficiency (NUE) Calculator

Nitrogen Use Efficiency tells you what fraction of the nitrogen you supplied actually ended up in the harvested crop. A low value means money and nitrogen are leaking to the environment; a very high value means you are mining the soil. This calculator works out NUE from yield, grain nitrogen content, and the nitrogen you applied, and benchmarks the result.

How it works

The crop’s nitrogen uptake is computed from yield and the nitrogen concentration of the harvested portion, then divided by the total nitrogen supplied:

uptake (N)  = yield × grain N content (%)
supplied(N) = fertilizer N + organic N + atmospheric deposition
NUE (%)     = uptake / supplied × 100

This is the classic apparent (or partial) recovery expression of efficiency. The tool also computes nitrogen balance as supplied − uptake, which is the surplus at risk of loss when positive, or the soil drawdown when negative.

Tips and example

A wheat crop yielding 8 t/ha of grain at 2.0 percent nitrogen takes up 160 kg N/ha. If you supplied 180 kg fertilizer N plus 20 kg from deposition and mineralized manure (200 kg total), NUE is 80 percent and the balance is a 40 kg/ha surplus. To raise NUE, split the application to match crop demand, use the right source for your soil pH, and incorporate or band urea to cut volatilization. Keep yield and nitrogen figures on the same area basis so the ratio is meaningful.