Nitrogen (N) fertilized or grazed grasslands in temperate regions of the Northern and Southern Hemisphere are important sources for atmospheric nitrous oxide (N2O). Following synthetic urine applications in a New Zealand grassland ecosystem, and ammonium (NH4+) and nitrate (NO3-) applications to a German grassland ecosystem, approximately 31, 16, and 5%, respectively, of the total emitted N2O (N2Otot) was produced by nitrification (N2Onit) with the rest being produced by denitrification (N2Oden). Analyses of the combined data set showed that 75% of all N2O emissions occurred above 60% water filled porosity (WFPS) and that more than 80% of all N2O emissions occurred at soil temperatures between 10¿ and 15¿C. N2Oden emissions were associated with a WFPS value at around 80% at relatively low NO3- concentrations, while N2Onit emissions only occurred at high NH4+ levels shortly after N application at soil temperatures around 10¿C. To increase the accuracy of predictions with simple mathematical models, such as the hole-in-the-pipe-model, long-term validation data sets are needed where driving variables are related to measured N2Onit and N2Oden data.