Estimation of nitrogen balances from agriculture for EU-15: spatialisation of estimates to river basins using the CORINE Land Cover

The objective of the study was the implementation of a soil surface agricultural nitrogen balance model to estimate surface nitrogen balances for both administrative and river basin areas across the whole European Union (EU-15) based on agricultural statistical data and coefficients of nitrogen content for crops, forages, manure, fertiliser and atmospheric deposition. CORINE Land Cover data is used to spatialise agricultural nitrogen estimates calculated for administrative areas to river basins. Results reported at the river basin level show a EU mean surplus of 60 kg N/ha. The distribution of the balances shows high surplus amounts in regions of intensive livestock farming (Flanders (B), the Netherlands, Brittany (FR)), and low or deficit values in the central areas of Spain, France and Italy. The effect of using the CORINE Land Cover to spatialise agricultural nitrogen balance estimates was also examined through scenario analysis. These simulations indicated a slight improvement in estimation when the CORINE Land Cover was used to spatialise N estimates from an administrative unit level to a finer one (e.g. NUTS2 to NUTS3). A sensitivity analysis of the coefficients of N content for harvested crops, manure and fertiliser showed a higher sensitivity of the model to crop related coefficients than manure coefficients. The overall sensitivity analysis revealed the need to improve the quality of the coefficients of N content, requiring more consistency and harmonisation, and moreover reflecting regional differences.