Estimation of ammonia and nitrous oxide emissions from turfgrass systems using a dynamic chamber method and a biogeochemical modeling framework
Alberth Nahas1, John T Walker2, Limei Ran3, Fred Yelverton4 and Viney Aneja5
Turfgrass management is characterized by intensive use of fertilizers, irrigation, and pesticides that contributes to reactive nitrogen emissions to the atmosphere. This work aimed to estimate ammonia (NH3) and nitrous oxide (N2O) emissions from turfgrass systems by combining measurements from field experiments and simulations from a biogeochemical model. Field experiments were conducted seasonally using a dynamic flux chamber on a 50 ft by 50 ft experimental plot of tall fescue at Lake Wheeler Turfgrass Field Laboratory, Raleigh, NC. Measurements indicate a wide range of emissions for NH3 (3.5-117.5 ng NH3-N m-2 s-1) and N2O (7.2-24.3 ng N2O-N m-2 s-1). Both NH3 and N2O emissions were higher during spring and summer, suggesting that the emissions are influenced by temperature-regulated soil processes (e.g., NH3 volatilization and microbially-driven denitrification). Meanwhile, the biogeochemical modeling simulations were performed using the Environmental Policy Integrated Climate (EPIC) model. The model utilized customized input files such as site information, daily weather data, soil physical and chemical characteristics, fertilizer types, and the site management options. Trace gas fluxes predicted by EPIC showed moderate to good correlation with measured fluxes (0.5-0.8) but tended to be biased low. Ongoing work seeks to refine the model configuration to reduce the observed bias. EPIC will then be used to explore optimal fertilization scenarios that balance turfgrass productivity with minimizing trace gas emissions.
1Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, acnahas@ncsu.edu
2Office of Research and Development, U.S. Environmental Protection Agency, RTP Campus, NC 27711, walker.johnt@epa.gov
3East Remote Sensing Laboratory, U.S. Department of Agriculture, Greensboro, NC 27104, limei.ran@usda.gov
4Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695, fred_yelverton@ncsu.edu
5Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC , vpaneja@ncsu.edu