The destruction of the greenhouse gas nitrous oxide (N2
O) by its reduction to dinitrogen via microbial denitrification in soil is poorly quantified, but better knowledge is needed to improve nitrogen (N) efficiency in agricultural ecosystems and lower polluting N losses to the environment including N2
O fluxes. We present a laboratory evaluation for the determination of N2
O reduction based on stable isotope values of soil emitted N2
O as a new approach to determine N2
O reduction in the field.