EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Bi-directional exchange of ammonia above a corn crop canopy: from flux measurements to model parameterizations

Alexander Moravek1,3, Saumya Singh1, Elizabeth Pattey2, Amy Hdrina1, Theodora Li1, Luc Pelletier2, Stuart Admiral2, and Jennifer Murphy1
Alexander Moravek et al.
  • 1University of Toronto, Department of Chemistry, Toronto, Canada
  • 2Agriculture and Agri-Food Canada, Ottawa, Canada
  • 3Umweltbundesamt, II 4.3 Air Quality and Terrestrial Ecosystems, Dessau-Roßlau, Germany (

Emissions of ammonia (NH3) from agriculture have a significant impact on the environment. Its atmospheric transport and subsequent deposition has been shown to alter nutrient-poor ecosystems thereby reducing biodiversity. As the most abundant base in the atmosphere, NH3 plays a key role in secondary aerosol formation impacting air quality and climate. Due to the lack of long term observations and challenges in performing NH3 flux measurements, large uncertainties exist in both emission quantification from fertilized crop fields and in the bi-directional exchange of NH3 with agroecosystems. We measured NH3 fluxes above a corn field using the eddy covariance technique together with a quantum cascade laser spectroscopy analyzer over two consecutive growing seasons in 2017 and 2018. We found that after initial NH3 emissions following fertilizer application, periods of both NH3 emission and deposition with similar flux magnitudes prevailed throughout the growing seasons (ranging approximately between ±300 ng m-2 s-1), highlighting the importance of the corn crop canopy for regulating the net NH3 exchange. To evaluate the underlying processes of the NH3 bi-directional exchange, a two-layer compensation point model was used. Based on the large range of environmental conditions encountered during the extensive flux measurements periods, the validity of different parameterizations could be assessed. In particular, processes regulating stomatal and non-stomatal flux pathways will be discussed.

How to cite: Moravek, A., Singh, S., Pattey, E., Hdrina, A., Li, T., Pelletier, L., Admiral, S., and Murphy, J.: Bi-directional exchange of ammonia above a corn crop canopy: from flux measurements to model parameterizations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15229,, 2021.

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