Annual N2O emission from a long-term compost field with seasonal ridge-furrow topography

Long-term compost addition often increases soil organic carbon (SOC) and improves soil structure, yet its effect on nitrous oxide (N 2 O) emissions remains uncertain. This study investigated N 2 O emissions from a 13-year compost amendment experiment with 11 Mg compost ha −1 year −1 on a sandy loam in Belgium. Emissions from a treatment with (Com) and without (NCom) compost addition were monitored over an entire year using static chambers. In year 13 since the start of the experiment, annual N 2 O emissions were slightly higher under Com than under NCom (5.361 vs. 4.835 kg N 2 O-N ha −1 ), but this difference was not statistically significant. Variation in soil mineral nitrogen content (N min ) and water filled pore space (WFPS) through time strongly shaped the temporal emission pattern. During the potato growing season under a ridge-furrow system, emissions were monitored separately for each of these field positions. Cumulative emissions from both positions did not differ significantly, likely because higher N min in the ridge was counterbalanced by lower WFPS, while the opposite was observed in the furrow position, showing lower N min and higher WFPS. Potato yield was not significantly affected by compost application. These findings suggest that long-term compost addition does not substantially increase annual N 2 O emissions, and that although ridges and furrows show different N min and WFPS, these shifts may not translate into significant differences in cumulative N 2 O emissions.