15N tracing has been applied to quantify rates of nitrogen transformations in soil and to distinguish the sources of the greenhouse gas nitrous oxide under different environmental conditions.
Due to enzymatic discrimination, natural 15N abundances change slightly in microbially mediated reactions in soil.
Apart from δ values, the site preference of 15N and 14N (isotopomers) for the inner or outer position within the nitrous oxide molecule has been used to determine its sources (nitrification or denitrification).
In agricultural soil, however, application of 15N enriched tracers, such as ammonium and nitrate, resembles conventional fertilisation practise.
[6] A numerical tool to study the nitrogen cycle is the Ntrace model based on a Markov chain Monte Carlo simulation.