Evaluation of ammonia air-surface exchange at the field scale: Improvement of soil and stomatal emission potential parameterizations

Nebila Lichiheb1, LaToya Myles2, Erwan Personne3, Mark Heuer4 and Michael Buban5

Intensive agriculture typically uses nitrogen-based fertilizers to increase yields for sustaining a growing human population.  Agriculture is the main source of atmospheric emissions of ammonia (NH3), a precursor to particulate matter in the atmosphere. The impact of NH3 emissions on air quality is of concern in the U.S. due to adverse effects on human health, and terrestrial and aquatic ecosystems. With reductions in nitrogen oxide emissions due to legislation implementation, the importance to NH3 for particulate matter formation and atmospheric deposition of reactive nitrogen has increased.  Emissions of NH3 from fertilized cropland occur as soon as fertilizer is applied on the farmed surface and emission can last from a few days to several weeks, depending on the properties of the specific fertilizer, plant properties, pedoclimatic conditions, environmental conditions, and agricultural practices. The complex interactions between agronomic and environmental conditions make necessary the use of modeling to study the NH3 volatilization.

In this study, we implemented in the SURFATM-NH3 model, which simulates the bi-directional exchanges of NH3 between the biogenic surface and the atmosphere, a new parameterization of the stomatal and ground layer emission potentials (Γs and Γg). This operational parameterization enables a dynamic modelling of Γs and Γg by taking into account the N status of the plant which includes the N input and the atmospheric N deposition.

This new parameterization was evaluated with a dataset comprising NH3 fluxes measured using the flux-gradient (FG) and relaxed eddy accumulation (REA) methods in a corn canopy fertilized with UAN and urease inhibitor NBPT over a period of approximately 3 months at the Energy Farm at the University of Illinois at Urbana‚ÄźChampaign, IL, USA. The results showed that the SURFATM- NH3 model satisfactorily simulates the NH3 fluxes by implementing the parameterization of Γs and Γg and by taking into account the effect of the urease inhibitor. The latter need to be more closely examined because it had a considerable effect on the rate and extent of NH3 volatilization.

 

1NOAA/ATDD, nebila.lichiheb@noaa.gov
2NOAA/ATDD, latoya.myles@noaa.gov
3INRA-AgroParisTech, erwan.personne@agroparistech.fr
4NOAA/ATDD/ORAU, mark.heuer@noaa.gov
5NOAA/ATDD/ORAU, michael.buban@noaa.gov