Nitrogen is an essential nutrient for all living beings. However, many compounds containing nitrogen are harmful for the environment. Plant species adapted to nutrient-poor conditions are displaced from forests and heathland. Emissions of nitrous oxide from over-fertilized fields exacerbate climate change. In many places, manure is responsible for nitrate concentrations in groundwater climbing above the limit values. Excessive levels of nitrogen dioxide in ambient air from transport sources present a risk to human health. This analysis shows that nitrogen pollution can be markedly reduced. Since agriculture accounts for around two-thirds of nitrogen emissions in Germany, efforts should focus on this sector.