Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2008
Publication Date: 9/10/2008
Citation: Jarecki, M.K., Parkin, T.B., Chan, A.K., Hatfield, J.L., Jones, R. 2008. Comparison of DAYCENT-Simulated and Measured Nitrous Oxide Emission from a Corn Field. Journal of Environmental Quality. 37:1685-1690. Interpretive Summary: Agricultural lands are a major source of the potent greenhouse gas nitrous oxide (N2O). Measuring N2O emissions from soil is an expensive, time consuming activity, therefore, mathematical models have been developed to predict N2O emissions. However, in order for the models to be useful they must be validated against measured data. This study was performed to compare simulated N2O emissions from a model with measured soil N2O emissions. We found that the general pattern of N2O emissions over time were simulated well by the model, however, the total amount of N2O released to the air was less with the model. There are many soil and environmental factors that interact to influence N2O production. Our results indicate that the model does not adquately mimic soil water dynamics and soil nitrogen transformations. If these components of the model could be improved, then better predictions of N2O emissions could be obtained. This information will be useful to scientists engaged in development of agricultural practices to reduce soil N2O emissions.
Technical Abstract: Accurate assessment of nitrous oxide (N2O) emission from soil requires continuous year-round and spatially extensive monitoring. Alternatively, simulation models can predict N2O fluxes based on climatic, soil and agricultural system input data. DAYCENT is an ecosystem model that simulates, among other processes, N2O emissions from soils. The purpose of the study was to compare N2O fluxes predicted by the DAYCENT model to measured N2O fluxes from an experimental corn field in Central Iowa. Also, soil water content and temperature simulated by DAYCENT were compared to measured values of these variables. Field N2O emissions were measured using four replicated automated chambers at 6 h intervals, over the period of DOY (day of year) 42 through DOY 254 of 2006. We observed that DAYCENT predicted soil temperature with high accuracy, with exception of winter when simulated temperatures tended to be lower than measured values. Volumetric water contents predicted by DAYCENT were generally underestimated during most of the experimental period. Daily N2O emissions simulated by DAYCENT were significantly correlated to field measured fluxes, however, time series analyses indicate that the simulated fluxes were out of phase with the measured fluxes. Cumulative N2O emission calculated from the simulations (2.31 kg N2O-N ha-1) was significantly different than measured cumulative N2O emission (4.26 +- 1.09 kg N2O-N ha-1). Discrepancies between measured and simulated fluxes may be due to inaccurate simulations of soil water content and soil N dynamics.