How the structure of agro-food systems shapes nitrogen, phosphorus, and carbon fluxes: The generalized representation of agro-food system applied at the regional scale in France.

The aim of the study was to develop a conceptual framework to analyze the agro-food system of French agricultural regions from the angle of N, P and C circulation through five major compartments (cropland, grassland, livestock biomass, local population and potential environmental losses). To reach that goal we extended the Generalized Representation of Agro-Food System approach to P and C and applied it to French regions. Using this methodology we analyzed the relation between production pattern and N surplus, P budget, and efficient organic carbon inputs (OC), assuming these three indicators to be good proxies for (i) N losses to waterbodies and the atmosphere, (ii) P accumulation or depletion in soils, and (iii) potential additional C sequestration in soils, respectively. A typology was then established, allowing for comparison between five types of agricultural systems. This made it possible to highlight that intensive specialized agricultural systems generate high environmental losses and resource consumption per unit of agricultural surface and present a very open nutrient cycle due to substantial trade flows. Conversely, mixed crop and livestock farming and extensive cropping systems had more limited N and P consumption and led to lower potential water and air contamination. However, this trend was reversed when expressing resource consumption and N and P budget on a pro rata basis of vegetal and animal product unit, reflecting the better nutrient use efficiency of specialized regions in their respective field of specialization. This study demonstrates the systemic impact of production patterns on environmental and agronomic performances at the regional scale.