Assessment of current and critical nitrogen inputs on European agricultural soils

The intensification of European agriculture, including large inputs of nitrogen (N) to soil by fertilizers and manure, has led to an increase in crop growth but also in various adverse effects. This includes: (i) loss of biodiversity in natural terrestrial ecosystems due to increased emission and deposition of ammonia (NH3), (ii) eutrophication of surface waters due to increased N runoff and (iii) increased nitrate (NO3) levels in drinking water reservoirs due to elevated N leaching. In this study we identified agricultural regions where current N inputs exceed critical N inputs at a high spatial resolution for the entire European Union using the INTEGRATOR model. Critical N inputs were derived on the basis of critical N losses, which in turn were based on critical levels of NH3 emission and critical N concentrations in leaching to ground water or runoff to surface water in view of the adverse impacts listed above. Results show that at EU-27 level, current N inputs slightly exceed critical N inputs in view of eutrophication by 15% for aquatic ecosystems and 25% for terrestrial ecosystems. We identified those places where there is a need to lower N losses to acceptable levels by increasing the nitrogen use efficiency (NUE).