Can N fertilizer use efficiency be estimated using 15N natural abundance?

Nitrogen fertilizer use efficiency can be estimated by using 15N enriched or 15N depleted synthetic fertilizers. However, it has also been proposed that differences in the relative natural 15N abundances (δ15N) of soil and fertilizer N can be used to estimate efficiency. This proposition is examined in this short communication on the basis of theory and published experimental data. The data did not support the concept that fertilizer use efficiency can be quantitatively estimated using δ15N data, because of isotopic fractionation during transformations and uptake of fertilizer-derived N in the soil-plant system. Isotopic fractionation (δ15N, ‰) was quantified by interpolation using fertilizer use efficiency estimated by 15N enrichment.