A farm level tool coupling farm, cropland and grassland models to assess the effect of farming practices on reactive nitrogen emissions and greenhouse gas balance and to define mitigation strategies

Agricultural systems, especially livestock systems, are a large source of emissions of grennhouse gas (nitrous oxide N2O, methane CH4, carbon dioxide CO2) and reactive nitrogen (ammonia NH3, nitrogen oxides NOx, nitrates NO3) in Europe. Several mitigation options, such as organic farming, have been suggested in the literature. But they mainly focused on a single gas and dealt with isolated processes. An integrated modelling tool has been developed to assess the effect of farm practices on reactive nitrogen and greenhouse gas emissions at the whole farm level. It couples the farm model FARMSIM with the cropland model CERES-EGC and the grassland model PASIM. To assess the contribution of a mechanistic crop model instead of crop emission factors, this integrated tool was compared with that initially developed in the GREENGRASS project and using the IPCC methodology for cropland emissions. Moreover, FARMSIM now includes a module taking into account emissions outside the farm boundaries. To illustrate the model behaviour, a ruminant livestock system was reconstructed from description of farming practices within an intensive dairy farm located in the north-east of France (INRA Mirecourt, Lorraine). As regards reactive nitrogen emissions and greenhouse balance gas balance, this conventional intensive farming system was compared with an associated system using mitigation options e.g., reducing fertilisers supply, reducing male calves number, modifying crop types. Further work is required to assess the model capabilities to predict nitrogen and carbon fluxes at the farm level. But this modelling tool shows promise to define and evaluate mitigation strategies at the whole farm level. Extending this approach at the landscape level meets Component 4 (Landscape analysis) of the NitroEurope projec