EGU2020-18120, updated on 12 Sep 2023
https://doi.org/10.5194/egusphere-egu2020-18120
EGU General Assembly 2020
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Decreasing trends of nitrogen export to waters in tile-drained landscapes are linked to a shifting water balance

Andreas Bauwe1, Petra Kahle1, Bärbel Tiemeyer2, and Bernd Lennartz1
Andreas Bauwe et al.
  • 1University of Rostock, Rostock, Germany (andreas.bauwe@uni-rostock.de)
  • 2Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany

In this study, time series over 14 years of climate, stream flow, land management, nitrate-nitrogen (NO3--N) concentrations and losses were analyzed to identify potential drivers for temporal trends at two tile-drained catchments under cropland use in northeastern Germany. Mean annual NO3--N concentrations were 9.7 (drainage plot) and 6.8 mg l-1 (ditch catchment), while mean annual NO3--N losses amounted to 22 and 20 kg ha-1, respectively. Results indicated decreasing trends for discharge, NO3--N concentrations and losses, and N surpluses at both the drainage plot and the ditch catchment scale. However, a significant downward trend was only detected for flow-weighted mean annual NO3--N concentrations of the ditch water. A significant positive relationship between annual discharge and mean annual NO3--N concentrations of the ditch underlines the importance of the hydrologic conditions on the NO3--N concentrations. No direct relationships were found between NO3--N concentrations and N surpluses. We conclude that the decreasing NO3--N concentrations could be primarily attributed to decreasing discharge rates. The possible impact of reduced N surpluses was overridden by the hydrologic conditions in the catchment. The statistically significant downward trend of flow-weighted mean annual NO3--N concentrations in the ditch water suggests, however, a positive effect of reduced N surpluses on stream water quality. Our analysis has further shown that effects of land management aiming at reducing N surpluses might only become visible with a delay of years or even decades.

How to cite: Bauwe, A., Kahle, P., Tiemeyer, B., and Lennartz, B.: Decreasing trends of nitrogen export to waters in tile-drained landscapes are linked to a shifting water balance, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18120, https://doi.org/10.5194/egusphere-egu2020-18120, 2020.