title: Nitrogen exchanges: testing the hypothesis of a country without agricultural production.
abstract: Today, finding data on agricultural nitrogen balances is quite easy. Calculations of such balances are carried out by most of the European countries as an indicator of environmental pollution attributable to the agricultural sector. In France, average values of agricultural nitrogen balances show an excess of 1.5 to 2 million tons of nitrogen. This excess is enormous. What would the balance of a country be if agricultural activity were stopped? In the following article, a country (France is used as an example) without agriculture is studied in order to assess its nitrogen balance. Using a previously published model describing nitrogen input and output of a given country, nitrogen flows are identified. Inputs include deposition, fixation, and products not intended for agricultural use. Outputs are reduced to zero if agriculture disappears (in France, agriculture is the only sector exporting products containing nitrogen). All flows are calculated considering the hypothesis of disappearance of agriculture. Nitrogen requirements to feed people and pets in France are estimated based on medical and veterinary data (recommended daily amounts for proteins and/or usual average consumption). Indeed, most of the food that nourishes the French population is produced nationally. If agriculture stops, it will be necessary to import food from foreign countries. Results show an unexpectedly high excess (for a country without agriculture having a structure similar to France: number of human beings and pets) of 1.5 million tons of nitrogen. An attempt to calculate an agricultural balance with the same data gives a result close to 3 million tons. Differences in French agricultural balances found in the literature can mainly be explained by values taken into account for deposition and fixation (values used here are at least 300,000 tons higher than values used by the Organisation for Economic Co-operation and Development). In conclusion, nitrogen excess in agriculture is partly due to social demand; agriculture does not only produce food but also includes many other functions (landscape management, employment, and preservation of culture, for example). As a consequence, efforts that do not involve suppressing agriculture should be made to figure out alternative ways of production.
authors.affiliation: Ecole Nationale d'Ingénieurs des Travaux Agricoles de Bordeaux, Laboratoire Sols et Paysages, Gradignan, France. slak@enitab.fr
authors.forename: M F
authors.initials: MF
authors.lastname: Slak
authors.forename: L
authors.initials: L
authors.lastname: Commagnac
authors.forename: P
authors.initials: P
authors.lastname: Pointereau
authors.forename: S
authors.initials: S
authors.lastname: Larbouret
authors.forename: C
authors.initials: C
authors.lastname: Lucas
authors.forename: S
authors.initials: S
authors.lastname: Muller
mesh_terms: D000383:Agriculture; D019649:Food Industry; D006801:Humans; D008962:Models, Theoretical; D009584:Nitrogen / Q000737:chemistry / Q000502:physiology*; D009586:Nitrogen Fixation / Q000502:physiology*; D012959:Socioeconomic Factors
chemical_list: D009584:Nitrogen