University of Illinois at Urbana-Champaign I Mark

Reactive nitrogen exchange between agricultural land and the atmosphere

Measurements of ammonia emissions from agricultural chemical fertilizer usage

Gaseous emissions of NH3 from volatilization following fertilizer application and throughout the 2014 growing season were measured in a maize field, in Central Illinois. NH3 fluxes above canopy were measured using the Relaxed Eddy Accumulation Method (REA). The method, originally introduced by Businger and Oncley (1989, J. Atmos. Ocean. Technol., 7:349-352) is based on conditional sampling of air masses, depending on the vertical motion of the atmosphere, as detected by a 3-dimensional sonic anemometer. Air is sampled through integrated samplers (denuders) for 4 hr periods.

Figure 4. Schematic of the REA system used to sample NH3 fluxes in a maze field, in Central Illinois.
Figure 5. REA system in the field.
Figure 6. Schematic of in-canopy system to measure NH3 fluxes, in a maize field in Central Illinois.
Figure 7. In-canopy denuders and miniature 3-D sonic anemometer in the field.

Modeling of NH3 emisssions from chemical fertilizer usage

Measurement of NH3 exchange between land and atmosphere is possible only in a limited number of locations. Modeling approaches are used to estimate NH3 emissions at the local, regional or global levels. Top down modeling approaches use available activity data (e.g. fertilizer sales) and emission factors (e.g., grams NH3 emitted per kilogram nitrogen equivalent applied for each fertilizer type) to estimate NH3 emissions. Process based models use detailed description of the physical, chemical and biological processes that lead to emissions of NH3 following fertilizer application.

Figure 8. Spatial variation of NH3 emissions in Central Illinois for 2002. Resolution 4 km x 4 km.
Figure 9. Temporal variation of NH3 emissions in Illinois for 2002-2011, estimated from the DNDC model compared to temporal factors assumed in SMOKE.

This material is based upon work supported by the National Science Foundation under Grant Number (NSF-1236814). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.