5 Hydrosystem Response to Agricultural Trajectories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.1 Aquifer Storage of Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.2 Riparian Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.3 Point and Diffuse Sources of Nutrients to the River System . . . . . . . . .. . . . . . . . . . . . . . . . 107
5.4 N and P Budget of the Water-Agro-Food System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6 Conclusion and Scenarios for the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.1 The Importance of Long-Term Storage Processes . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 109
6.2 The Importance of the Structural Pattern of Agro-Food Systems
on the Environmental Imprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Abstract Based on the GRAFS method of biogeochemical accounting for nitrogen
(N), phosphorus (P) and carbon (C) fluxes through crop, grassland, livestock and
human consumption, a full description of the structure and main functioning features
of the French agro-food system was obtained from 1850 to the present at the scale
of 33 agricultural regions. For the period since 1970, this description was compared
with the results of an agronomic reconstitution of the cropping systems of the
Seine watershed based on agricultural census and detailed enquiries about farming
practices at the scale of small agricultural regions (the ARSeine database), which
were then used as input to an agronomical model (STICS) calculating yields, and
the dynamics of N and C. STICS was then coupled with a hydrogeological model
(MODCOU), so that the entire modelling chain can thus highlight the high temporal
inertia of both soil organic matter pool and aquifers. GRAFS and ARSeine revealed
that the agriculture of the North of France is currently characterised by a high degree
of territorial openness, specialisation and disconnection between crop and livestock
farming, food consumption and production. This situation is the result of a historical
trajectory starting in the middle of the nineteenth century, when agricultural systems
based on mixed crop and livestock farming with a high level of autonomy were
dominant. The major transition occurred only after World War II and the implementation of the Common Agricultural Policy and led, within only a few decades, to
a situation where industrial fertilisers largely replaced manure and where livestock
farming activities were concentrated either in the Eastern margins of the watershed
in residual mixed farming areas or in specialised animal production zones of the
Great West. A second turning point occurred around the 1990s when regulatory
measures were taken to partly correct the environmental damage caused by the
preceding regime, yet without in-depth change of its logic of specialisation and
intensification. Agricultural soil biogeochemistry (C sequestration, nitrate losses, P
accumulation, etc.) responds, with a long delay, to these long-term structural
changes. The same is true for the hydrosystem and most of its different compartments (vadose zone, aquifers, riparian zones), so that the relationship between the
diffuse sources of nutrients (or pesticides) and the agricultural practices is not
immediate and is strongly influenced by legacies from the past structure and
practices of the agricultural system. This has strong implications regarding the
possible futures of the Seine basin agriculture.
Keywords Agriculture, Aquifers, Carbon, Denitrification, Fertilisers, Greenhouse
gases, Leaching, Nitrogen, Nutrients, Phosphorus, Riparian wetlands, Soil
92
G. Billen et al.
5.1 Aquifer Storage of Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.2 Riparian Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.3 Point and Diffuse Sources of Nutrients to the River System . . . . . . . . .. . . . . . . . . . . . . . . . 107
5.4 N and P Budget of the Water-Agro-Food System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6 Conclusion and Scenarios for the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.1 The Importance of Long-Term Storage Processes . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 109
6.2 The Importance of the Structural Pattern of Agro-Food Systems
on the Environmental Imprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Abstract Based on the GRAFS method of biogeochemical accounting for nitrogen
(N), phosphorus (P) and carbon (C) fluxes through crop, grassland, livestock and
human consumption, a full description of the structure and main functioning features
of the French agro-food system was obtained from 1850 to the present at the scale
of 33 agricultural regions. For the period since 1970, this description was compared
with the results of an agronomic reconstitution of the cropping systems of the
Seine watershed based on agricultural census and detailed enquiries about farming
practices at the scale of small agricultural regions (the ARSeine database), which
were then used as input to an agronomical model (STICS) calculating yields, and
the dynamics of N and C. STICS was then coupled with a hydrogeological model
(MODCOU), so that the entire modelling chain can thus highlight the high temporal
inertia of both soil organic matter pool and aquifers. GRAFS and ARSeine revealed
that the agriculture of the North of France is currently characterised by a high degree
of territorial openness, specialisation and disconnection between crop and livestock
farming, food consumption and production. This situation is the result of a historical
trajectory starting in the middle of the nineteenth century, when agricultural systems
based on mixed crop and livestock farming with a high level of autonomy were
dominant. The major transition occurred only after World War II and the implementation of the Common Agricultural Policy and led, within only a few decades, to
a situation where industrial fertilisers largely replaced manure and where livestock
farming activities were concentrated either in the Eastern margins of the watershed
in residual mixed farming areas or in specialised animal production zones of the
Great West. A second turning point occurred around the 1990s when regulatory
measures were taken to partly correct the environmental damage caused by the
preceding regime, yet without in-depth change of its logic of specialisation and
intensification. Agricultural soil biogeochemistry (C sequestration, nitrate losses, P
accumulation, etc.) responds, with a long delay, to these long-term structural
changes. The same is true for the hydrosystem and most of its different compartments (vadose zone, aquifers, riparian zones), so that the relationship between the
diffuse sources of nutrients (or pesticides) and the agricultural practices is not
immediate and is strongly influenced by legacies from the past structure and
practices of the agricultural system. This has strong implications regarding the
possible futures of the Seine basin agriculture.
Keywords Agriculture, Aquifers, Carbon, Denitrification, Fertilisers, Greenhouse
gases, Leaching, Nitrogen, Nutrients, Phosphorus, Riparian wetlands, Soil
92
G. Billen et al.