Concilier efficacité technico-économique et environnementale des exploitations agricoles en zone vulnérable : apport du diagnostic agraire

How to conciliate the technico-economic and the environmental efficiency of farms in a difficult environment : role of the agrarian diagnosis

In the Breton département of Côtes d'Armor, the bay of Saint-Michel-en-Grève has been repeatedly subjected to 'green slicks' due to the eutrophication of the rivers of this dairying region. The agrarian diagnosis makes it possible to forecast how the practices will evolve globally, with a historical approach, taking into account both the technico-economical and the environmental aspects. This diagnostic analysis was linked to the setting-up of an environmental model. It has thrown light on the specificity of this coastal region, where the pedo-climatic conditions are conducive to the production of forage, thus explaining the predominance of dairy farming. The grassland farming systems remain competitive, but their development is hampered by the parcelled-out field pattern. There are two evolutive scenarii simulated by the TNT2 model: continuation of the present practices with a fertilisation already reduced by 30%, or a forage system with limited inputs; neither is able to bring about a lowering of the nitrate content in the river to the desired level. It is therefore really necessary to build up together innovating production systems, so as to make the farms economically and environmentally sustainable.