<p>There is still an urgent need to reduce nitrogen inputs into surface water and groundwater. This study examines ammonium and nitrate losses from agricultural grasslands into connected drainage ditches of the northwest German coastal region. For this purpose, the soils of the characteristic geest, peatland, and marsh area landscapes are analyzed for ammonium and nitrate contents. In addition, surface drainage, subsurface drainage and ditch waters are analyzed for ammonium and nitrate concentrations. The peatlands are divided into bogs, fens and organo-mineral transition sites. High ammonium contents are found primarily in peat soils and organo-mineral soils, with values between 22.2 and 25.9 kg NH₄⁺-N ha⁻¹ in 0–30 cm depth. Lower contents are found in the mineral-dominated soils of the geest and marsh areas. Ammonium losses through surface drainage mainly occur from soils of the geest area with a&#xa0;mean value of 4.7 NH₄⁺-N mg l⁻¹ and via subsurface drainage primarily from fens and raised peatland bogs, with concentrations of&#xa0;3.9 and 2.3 NH₄⁺-N mg l⁻¹. The ditches adjacent to fen sites also show the highest ammonium concentrations with 3.5 mg NH₄⁺-N l⁻¹. The nitrate contents of the soils are similar across all landscape areas. The highest contents are found in fens and organo-mineral sites, with values of 21.4 and 20.3 kg NO₃⁻-N ha⁻¹, respectively. Nitrate occurs in highest concentrations within surface drainage with 4.4 mg NO₃⁻-N l⁻¹ as well as in subsurface drainage with 4.6 mg NO₃⁻-N l⁻¹ from geest soils. This is also reflected in the ditches of the geest, with the highest mean NO₃⁻-N concentrations of 3.3 mg NO₃⁻-N l⁻¹. Soil organic matter was identified as a&#xa0;significant influence factor for the leaching of ammonium and nitrate. In addition, the amount and timing of N&#xa0;fertilization also play a&#xa0;significant role.</p>