Our manuscript reports on an extensive field study carried out between August and December 2017. Along with thorough soil analysis and meteorological observations, the concentration and isotopic composition of soil emitted nitrous oxide (N2O) was measured above a grassland site in Central Switzerland. Automated flux-chambers were coupled to a custom-built preconcentration and laser spectroscopy based on-line measurement method, a cutting- edge combination that could be achieved for the first time to the best of our knowledge. The obtained results were used to validate a recently developed isotope sub module (SIMONE) for a biogeochemical model (LandscapeDNDC), to simulate fluxes of trace gases. Our results show a clear predominance of denitrification as the primary N2O emitting source process. In contrast to previous studies, this dominance led to stable N2O site preference values through-out the measurement campaign, a feature that was also represented by SIMONE. These findings will bridge current shortcomings in our model understanding and thereby help developing targeted N2O mitigation strategies.