Assessment of N2O emissions from rapeseed cultivation in Poland by various approaches

The aim of this study was to compare four tools for calculation of nitrous oxide (N2O) emissions under the renewable energy directive. All the tools follow the methodology of the international panel on climate change. The first calculations of N2O fluxes were based on the Tier 1 method using the BioGrace tool. The second and the third ones followed the Tier 2 methodology, applying the global nitrous oxide calculator and the Lesschen emission factors, respectively. The last assessment was performed in accordance with the Tier 3 approach by using the denitrification-decomposition model. The N2O fluxes were calculated for rapeseed cultivation in a 4-year crop rotation in Poland. The same input data were applied in all methods. The average of N2O emissions varied in the range of 1.99-3.78 kg N2O ha-1 y-1, depending on the approach used (Lesschen emission factors > denitrification-decomposition > global nitrous oxide calculator > BioGrace). This paper illustrates that, at country level, the Lesschen emission factors method worked as well as the denitrification-decomposition model for Poland. The advantage of this approach is the simplicity of collecting the necessary data, in contrast to process-based modelling. Moreover, the Tier 2 method provides mitigation measures similar to the denitrification-decomposition model, related to crop type, climatic conditions, and management practices.