EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Importance of in-situ measurements of both N2O and N2 emissions to calibration of biogeochemical models to simulate N budgets

Naoya Takeda1, Johannes Friedl1, David Rowlings1, Clemens Scheer1,2, Edwin Haas2, David Kraus2, and Peter Grace1
Naoya Takeda et al.
  • 1Queensland University of Technology, Centre for Agriculture and the Bioeconomy, Sustainable Agroecosystems, Australia (
  • 2IMK-IFU, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany

Denitrification is a key process in the global nitrogen (N) cycle, causing nitrous oxide (N2O) and dinitrogen (N2) emissions. Even though denitrification is assumed to be a major N loss pathway from agroecosystems, field-scale estimates of both N2O and N2 are scarce, reflecting methodological difficulties in measuring and upscaling N2 emissions. Mechanistic biogeochemical models allow estimates of seasonal denitrification losses at the field scale, extrapolating important yet often limited experimental results. However, such predictions rely mostly on N2O data, meaning that the lack of N2 data hinders the validation of overall denitrification rates, which remain a major uncertainty for N budgets.

This study investigated denitrification losses and N budgets in two subtropical sugarcane systems using Agricultural Production Systems sIMulator (APSIM) with unique datasets of both N2O and N2 emissions measured in the field with the 15N gas flux method and upscaled over the growing season. Five key soil N parameters in APSIM were identified as influential on N2O and N2 emissions via global sensitivity analysis, followed by generalised likelihood uncertainty estimation to determine their posterior distributions using (i) both N2O and N2 data and (ii) N2O data only.

For both approaches, the calibration of APSIM led to larger denitrification (N2O+N2) losses and a shift towards N2 compared to the use of default parameters. Simulated N2O emissions did not differ between the different calibration approaches. However, simulated N2 emissions were larger and agreed better with the observed values when calibrated with both N2O and N2 consistently across sites. This approach also improved the simulation of fertiliser N losses via denitrification, leaching and runoff, compared to the observed fertiliser 15N loss at harvest.

These findings indicate that biogeochemical models commonly used with default soil N parameters or calibration limited to N2O data are likely to underestimate denitrification losses, producing a bias in simulations of N budgets. Our findings also highlight the importance to integrate in-situ measurements of N2O and N2 in simulation exercises, and demonstrate how innovative isotope methods can be used to inform biogeochemical models, ensuring more accurate N budget estimates across scales.

How to cite: Takeda, N., Friedl, J., Rowlings, D., Scheer, C., Haas, E., Kraus, D., and Grace, P.: Importance of in-situ measurements of both N2O and N2 emissions to calibration of biogeochemical models to simulate N budgets, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4849,, 2023.