Nutrient Use Efficiency

Nutrient use efficiency (NUE) measures how effectively crops use supplied nutrients to produce yield. In fertiliser management, it relates crop yield or nutrient uptake to nutrient input; its precise meaning depends on the indicator used, so it is not always simply the percentage of applied fertiliser absorbed by a crop.

How nutrient use efficiency is measured

Different indicators distinguish total productivity from the additional benefit attributable to fertiliser application.

• Partial factor productivity is crop yield divided by the quantity of fertiliser nutrient applied. For example, 4,000 kg of grain produced with 100 kg of applied nitrogen gives 40 kg of grain per kg of nitrogen.
• Agronomic efficiency is the increase in yield over a plot receiving none of the nutrient being evaluated, divided by the quantity of that nutrient applied.
• Apparent recovery efficiency is the increase in crop nutrient uptake over a plot receiving none of that nutrient, divided by the quantity applied; multiplying this ratio by 100 expresses it as a percentage.
• Calculations use the quantity of the nutrient, not merely the total weight of the fertiliser product.

What determines efficiency

Adding more fertiliser does not necessarily produce a proportionate increase in yield. Efficiency depends on whether nutrient supply matches crop requirements and whether other growing conditions permit its use.

• Balanced nutrition matters because a shortage of one essential nutrient can limit the response to another.
• Soil properties, moisture availability, crop variety, and the timing and placement of fertiliser influence nutrient uptake.
• Nutrients may become unavailable to the crop through fixation in soil or may be lost through leaching, runoff or gaseous emissions, depending on the nutrient and field conditions.

Why improving efficiency matters

Higher NUE can sustain crop production with less avoidable nutrient loss and lower fertiliser expenditure per unit of output. It also helps reduce pollution associated with excessive or poorly managed fertiliser application.

• Soil-test-based recommendations help align nutrient application with soil fertility and crop needs.
• Applying the right source, rate, time and place helps match nutrient availability with crop demand.
• Integrated nutrient management combines fertilisers with organic manures and other suitable nutrient sources to support soil fertility and efficient nutrient use.