Materials Accounting as a Policy Tool for Nutrient Management in the Danube Basin

Nutrient management has to consider both: Nutrients as essential elements for the biosphere with limited resources and nutrients as potential environmental pollutants (eutrophication, groundwater-deterioration). Materials Accounting techniques enable to describe and quantify the metabolism of Nitrogen and Phosphorus in large river Basins, such as the Danube Basin. By knowing the sources and pathways of nutrients it is possible (i) to identify the key causes of pollution problems and (ii) to point out inefficient use of the limited resource “nutrients”. Additionally, it is possible to design efficient measures based on nutrient balances. Materials Accounting observes the changes of stocks within a time interval. Therefore, it allows the early recognition of the accumulation and depletion of harmful substances (e.g. Nitrate in the groundwater) or of limited resources (e.g. P in topsoils) in the environment. In combination with scenario development Materials Accounting has a high predictive power. There is a substantial difference in designing the most efficient measures for reducing nutrient inputs or to optimise the use of limited resources in the entire Danube Basin and in individual countries.