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Biogeochemical functioning and trajectories of French territorial agricultural systems : carbon, nitrogen and phosphorus fluxes (1852-2014)

Abstract : This work investigates agricultural systems from the angle of nitrogen (N), phosphorus (P) and carbon (C) fluxes in French regions from 1852 to 2014, following a socio-metabolic approach stressing out the underlying logic behind these material fluxes. Results brought out by this research highlight the systemic relation between production pattern and N and P balances, and changes in soil organic C stocks in agricultural soil. Intensive specialized agricultural systems generate high environmental losses and resource consumption per unit agricultural surface and present largely open nutrient cycles due to substantial trade flows. Conversely, integrated crop and livestock farming have more limited N and P consumption and lead to lower air and water contamination. Long-term analysis shows that only after the Second World War, under the pressure of strong interventionist policies, some French regions specialized into crop or livestock farming. Particularly, the period from the 1950’s to the 1980’s was marked by a concomitant acceleration in crops yields, livestock production and use of mineral fertilizers. This resulted in increased N and P balances over cropland and grassland and growing C inputs to cropland, causing important losses of N to the hydrosphere and atmosphere, together with the accumulation of P and C stocks in soils. However, C accumulation resulting from increased crop production was permitted by the increased recourse to mineral fertilizers and agricultural machinery which consumes fossil-fuel energy. Therefore, C storage in cropland was a side-effect of the shift from an energy metabolism based on solar energy to one based on fossil-fuel combustion.
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  • HAL Id : tel-02355318, version 1

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Julia Le Noë. Biogeochemical functioning and trajectories of French territorial agricultural systems : carbon, nitrogen and phosphorus fluxes (1852-2014). Biodiversity and Ecology. Sorbonne Université, 2018. English. ⟨NNT : 2018SORUS159⟩. ⟨tel-02355318⟩

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