Enhancing the soil and water assessment tool model for simulating N ₂ O emissions of three agricultural systems

Abstract

Nitrous oxide (N 2 O) is a potent greenhouse gas (GHG) contributing to global warming, with the agriculture sector as the major source of anthropogenic N 2 O emissions due to excessive fertilizer use. There is an urgent need to enhance regional-/watershed-scale models, such as Soil and Water Assessment Tool (SWAT), to credibly simulate N 2 O emissions to improve assessment of environmental impacts of cropping practices. Here, we integrated the DayCent model's N 2 O emission algorithms with the existing widely tested crop growth, hydrology, and nitrogen cycling algorithms in SWAT and evaluated this new tool for simulating N 2 O emissions in three agricultural systems (i.e., a continuous corn site, a switchgrass site, and a smooth brome grass site which was used as a reference site) located at the Great Lakes Bioenergy Research Center (GLBRC) scale-up fields in southwestern Michigan. These three systems represent different levels of management intensity, with corn, switchgrass, and smooth brome grass (reference site) receiving high, medium, and zero fertilizer application, respectively. Results indicate that the enhanced SWAT model with default parameterization reproduced well the relative magnitudes of N 2 O emissions across the three sites, indicating the usefulness of the new tool (SWAT-N 2 O) to estimate long-term N 2 O emissions of diverse cropping systems. Notably, parameter calibration can significantly improve model simulations of seasonality of N 2 O fluxes, and explained up to 22.5%-49.7% of the variability in field observations. Further sensitivity analysis indicates that climate change (e.g., changes in precipitation and temperature) influences N 2 O emissions, highlighting the importance of optimizing crop management under a changing climate in order to achieve agricultural sustainability goals.Citation: Yang, Q., X. Zhang, M. Abraha, S. Del Grosso, G. P. Robertson, and J. Chen. 2017. Enhancing the soil and water assessment tool model for simulating N 2 O emissions of three agricultural systems. Ecosystem Health and Sustainability 3(2):e01259.

Predicting nitrous oxide emissions after the application of solid manure to grassland in the United Kingdom

“…However, there was a magnitude of discrepancy if compared with the range of .13–.17 in Yang et al. (). This could be explained because our modeling approach was not the same as that of Yang et al.…”

“…This could be explained because our modeling approach was not the same as that of Yang et al. (). Since both approaches were still empirical, the parameterization is a compromise between reality, feasibility, and simplicity.…”

“…Therefore, the results showed that the model is robust and convincing if we consider that there is a big difference in site environments between the United Kingdom and Canada. However, there was a magnitude of discrepancy if compared with the range of .13-.17 in Yang et al (2017). This could be explained because our modeling approach was not the same as that of Yang et al (2017).…”

“…Yang et al. () indicated that the SWAT model satisfactorily reproduced the relative magnitude of N 2 O emissions across three agricultural systems in North America, including from different grasslands. From the WFPS results, it is thus evident that the SWAT model, after careful parameterization, can simulate soil moisture dynamics very well.…”

“…Because the Soil and Water Assessment Tool (SWAT) model is a widely used hydrological model of nonpoint sources, it has advantages in simulating hydrologic cycles at a watershed scale. Recently, the SWAT model has been modified to predict N 2 O flux via coupling with models of the nitrification and denitrification processes (Bhanja, Wang, Shrestha, & Zhang, ; Wagena, Bock, Sommerlot, Fuka, & Easton, ; Yang et al., ). However, all of the above models of SWAT‐based N 2 O emissions were validated only in North America.…”