Nitrogen budgets – tools to validate information on nitrogen fluxes

Wilfried Winiwarter

Reactive nitrogen compounds, released by anthropogenic activities, may take different pathways in the environment, not all of which are easily traceable. Nitrogen budgets allow using surrogate information for fluxes that otherwise cannot easily be measured or validation of flux quantities for which an independent second set of data can be made available. In order to reliably assess nitrogen budgets and to make them comparable, the harmonization of approaches is required. Such a harmonizing effort has been performed under the European “air quality” convention, the Convention on Long-Range Transboundary Air Pollution. Based on existing efforts to collect data on fluxes of nitrogen compounds, specifically in the framework of the convention, from national greenhouse gas inventories mandatory under UNFCCC, or in connection with European activities of EUROSTAT or OECD, a guidance document has been developed to allow assessing national nitrogen budgets. Eight individual “pools” have been identified that are considered the start- and endpoints of environmental fluxes. The guidance document allows to properly assign and quantify fluxes between pools and cares for a consistent nomenclature. This presentation demonstrates complete and partial applications of the concept, and demonstrates the advantages of harmonizing approaches. It takes available published budgets for several European and non-European countries, analyzes them for compatibility, and evaluates nitrogen budgets for their potential contribution to a sustainable development of agriculture and beyond agriculture. Downscaling national to regional budgets, and comparing to the concept of farm-scale budgets (farm scale as well as soil budgets) will conclude the analysis.