The anthropogenic nitrogen cycle is characterized by a high complexity. Different reactive nitrogen species (NH3, NH4+, NO, NO2, NO3−, and N2O) are set free by a large variety of anthropogenic activities and cause numerous negative impacts on the environment. The complex nature of the nitrogen cycle hampers public awareness of the nitrogen problem. To overcome this issue and to enhance the sensitivity for policy action, we developed a new, impact-based integrated national target for nitrogen (INTN) for Germany. It is based on six impact indicators, for which we derived the maximum amount of nitrogen losses allowed in each environmental sector to reach related state indicators on a spatial average for Germany. The resulting target sets a limit of nitrogen emissions in Germany of 1053 Gg N yr−1. It could serve as a similar means on the national level as the planetary boundary for reactive nitrogen or the 1.5 °C target of the climate community on the global level. Taking related uncertainties into account, the resulting integrated nitrogen target of 1053 Gg N yr−1 suggests a comprehensible INTN of 1000 Gg N yr−1 for Germany. Compared to the current situation, the overall annual loss of reactive nitrogen in Germany would have to be reduced by approximately one-third.

Emissions of reactive nitrogen (Nr) give rise to a wide range of environmental problems. Nitrogen budgets for various systems and on different scales are an established tool to quantify the sources and fate of Nr. The national nitrogen budget (NNB) for Germany calculates the nitrogen flows for eight pools: Atmosphere, Energy and Fuels, Material and Products in Industry, Humans and Settlements, Agriculture, Forest and Semi-natural Vegetation, Waste, and Hydrosphere, as well as for the transboundary N-flows. In Germany, in total 6,275 kt Nr a−1 has been introduced into the nitrogen cycle annually (mean 2010 to 2014), of which 43% stem from ammonia synthesis. Domestic extraction and import of nitrogenous fossil fuels (lignite, coal, crude oil) releases another 2,335 kt Nr a−1. Import of food, feed and materials contributes 745 kt Nr a−1, while biological N fixation converts 308 kt Nr a−1 into organically bound nitrogen. In terms of Nr sinks, the combustion and denoxing of fuels and the refining of crude oil converts 2,594 kt Nr a−1 to N2. In waters, soils, and wastewater treatment plants, denitrification leads to the release of 1,107 kt Nr a−1 as N2. Via the atmosphere and hydrosphere, Germany exports 755 kt Nr a−1 to neighbouring countries and into coastal waters. On balance, Germany releases 1,627 kt Nr a−1 annually to the environment. However, the NNB as a whole and the individual pool balances involve substantial uncertainties, which have to be considered when interpreting the results.