N2O emissions from a fertilized humid grassland near Cork, Ireland were continuously measured during 2003 using an eddy covariance system. For most of the year emissions were close to zero and 60% of the emissions occurred in eight major events of 2–20 days’ duration. Two hundred and seven kg ha−1 of synthetic N and 130 kg ha−1 organic N were applied over the year and the total measured annual N2O emission was 11.6 kg N ha−1. The flux data were used to test the prediction of N2O emissions by the DNDC (DeNitrification – DeComposition) model. The model predicted total emissions of 15.4 kg N ha−1, 32 % more than the observed emissions. On this basis the model was further used to simulate (a) background (non-anthropogenic) N2O emissions and (b) the effect on N2O emissions of future climate perturbations based on the Hadley Center model output of the IS92a scenario for Ireland. DNDC predicts 1.7 kg N ha−1 year−1 of background N2O emissions, accounting for 15% of the observed emissions. Climate shifts will increase total annual modeled N2O emissions from 15.4 kg N ha−1 to 22.4 kg N ha−1 if current levels of N applications are maintained, or to 21.2 kg N ha−1 if synthetic N applications are reduced to 170 kg N ha−1 to comply with recent EU water quality legislation. Thus the projected increase in N2O emissions due to climate change is far larger than the decrease expected from reduced fertilizer applications.
Climate change DNDC model Emission factor Nitrogen fertilizer Nitrous oxide