Comparing Soil Nitrous Oxide Emissions Simulated by the New Freeze-Thaw Version of DayCent with Fluxes Inferred from Atmospheric Inversion

Citation

Del Grosso, S. J., Ogle, S. M., Parton, W. J., Nevison, C. D., Smith, W., Grant, B., Wagner-Riddle, C., Tenuta, M. Comparing Soil Nitrous Oxide Emissions Simulated by the New Freeze-Thaw Version of DayCent with Fluxes Inferred from Atmospheric Inversion. American Geophysical Union, Fall Meeting, abstract #B24C-06, Washington, D.C., December 2018

Plain language summary

Soil nitrous oxide emissions from agricultural management are a key greenhouse gas source in many countries due to the widespread use of nitrogen fertilizers, manure amendments from livestock production, growing legumes and other practices that contribute nitrogen inputs to soils. In addition, recent observational studies show that emissions associated with freeze-thaw cycles during spring often are responsible for a large portion of annual emissions in northern systems. The DayCent model was recently modified to represent the freeze-thaw induced emissions triggered by snow pack melting. The new model was parametrized using site level data from three field studies: a corn-soy-wheat rotation in Ontario, a corn-faba-spring wheat rotation in Manitoba, and an irrigated continuous corn system in Colorado. Comparisons with N2O observations using standard statistics (correlation coefficient, root mean square error, bias) showed that the revised model performed better than the standard version of DayCent. The revised model was then used to simulate N2O emissions from agricultural soils across the US and compared with emissions estimated using Lagrange regional inversion during 2007-2012. Both DayCent and inversions showed substantial N2O peaks during early summer associated with fertilizer additions, as well as large peaks during spring except for winters with below average snowfall. To our knowledge, this is the first national scale comparison of N2O emissions using a bottom up biogeochemical model with top down inversion. The observed consistency increases confidence in model generated emissions and should lead to better estimates of emissions reported in national inventories.

Abstract

Soil nitrous oxide emissions from agricultural management are a key greenhouse gas source in many countries due to the widespread use of nitrogen fertilizers, manure amendments from livestock production, growing legumes and other practices that contribute nitrogen inputs to soils. In addition, recent observational studies show that emissions associated with freeze-thaw cycles during spring often are responsible for a large portion of annual emissions in northern systems. The DayCent model was recently modified to represent the freeze-thaw induced emissions triggered by snow pack melting. The new model was parametrized using site level data from three field studies: a corn-soy-wheat rotation in Ontario, a corn-faba-spring wheat rotation in Manitoba, and an irrigated continuous corn system in Colorado. Comparisons with N2O observations using standard statistics (correlation coefficient, root mean square error, bias) showed that the revised model performed better than the standard version of DayCent. The revised model was then used to simulate N2O emissions from agricultural soils across the US and compared with emissions estimated using Lagrange regional inversion during 2007-2012. Both DayCent and inversions showed substantial N2O peaks during early summer associated with fertilizer additions, as well as large peaks during spring except for winters with below average snowfall. To our knowledge, this is the first national scale comparison of N2O emissions using a bottom up biogeochemical model with top down inversion. The observed consistency increases confidence in model generated emissions and should lead to better estimates of emissions reported in national inventories.

Publication date

2018-12-15