Closing the N-Budget: How Simulated Groundwater-Borne Nitrate Supply Affects Plant Growth and Greenhouse Gas Emissions on Temperate Grassland

• Published in: Atmosphere Vol. 9; no. 10; p. 407
• Main Authors: Liebermann, Ralf, Breuer, Lutz, Houska, Tobias, Klatt, Steffen, Kraus, David, Haas, Edwin, Müller, Christoph, Kraft, Philipp
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-10-2018
• Subjects: Agriculture; Agrochemicals; Animal manures; biogeochemical ecosystem model; Biogeochemistry; Biological fertilization; biomass production; Calibration; Carbon cycle; Carbon dioxide; Carbon dioxide emissions; Computer simulation; Ecosystem models; Ecosystems; Emission analysis; Emissions; Farm buildings; Farmyard manure; Fertilization; Fertilizers; Grasslands; Greenhouse effect; Greenhouse gases; Groundwater; Groundwater reservoirs; Hydrology; Investigations; Moisture content; Nitrates; Nitrogen; Nitrous oxide; Plant biomass; Plant growth; sensitivity analysis; Soil; soil moisture; Soil water; Surface water; Transport; uncertainty assessment; Uptake; Water content; Water pollution; Germany
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos9100407

European groundwater reservoirs are frequently subject to reactive nitrogen pollution (Nr) owing to the intensive use of nitrogen (N) fertilizer and animal manure in agriculture. Besides its risk on human health, groundwater Nr loading also affects the carbon (C) and N cycle of associated ecosystems. For a temperate grassland in Germany, the long-term (12 years) annual average exports of Nr in form of harvest exceeded Nr inputs via fertilization and deposition by more than 50 kgN ha−1. We hypothesize that the resulting deficit in the N budget of the plant-soil system could be closed by Nr input via the groundwater. To test this hypothesis, the ecosystem model LandscapeDNDC was used to simulate the C and N cycle of the respective grassland under different model setups, i.e., with and without additional Nr inputs via groundwater transport. Simulated plant nitrate uptake compensated the measured N deficit for 2 of 3 plots and lead to substantial improvements regarding the match between simulated and observed plant biomass and CO2 emission. This suggests that the C and N cycle of the investigated grassland were influenced by Nr inputs via groundwater transport. We also found that inputs of nitrate-rich groundwater increased the modelled nitrous oxide (N2O) emissions, while soil water content was not affected.