EGU2020-2221
https://doi.org/10.5194/egusphere-egu2020-2221
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Source-process partitioning of soil N2O and CO2 production: nitrogen and simulated exudate additions

Erin Daly and Guillermo Hernandez Ramirez
Erin Daly and Guillermo Hernandez Ramirez
  • University of Alberta, Renewable Resources, Canada (edaly@ualberta.ca)

Understanding the source partitioning of carbon dioxide (CO2) and nitrous oxide (N2O) fluxes from soil is integral for the characterization of total fluxes and the quantification of potential soil organic matter priming effects. Additionally, we utilized 15N-N2O site preference data to analyze the process priming of microbial nitrification and denitrification on subsequent N2O fluxes. A 32-day laboratory incubation was designed to examine the effects of artificial exudate, nitrogen fertilizer and their potential interactive effects on CO2 and N2O fluxes, soil organic matter source-priming and N2O process-priming. Artificial root exudate (ARE) consisting of a mixture of 99 atom% 13C labelled compounds at three addition rates (0, 6.2, 12.5 mg C kg-1 soil day-1) was applied daily for 21 days to microcosms with or without urea fertilizer, a subset of which was labelled with 5 atom % 15N. Measurements of CO2 and N2O fluxes, isotopic composition and N2O site preference were frequent throughout the duration of the experiment. Source partitioning of CO2 fluxes showed that soil organic carbon (SOM-C) positive priming was significantly altered by additions of artificial exudate and urea (p < 0.001 and 0.001, respectively). When applied concurrently, urea addition had an antagonistic interactive effect on SOM-C sourced CO2 fluxes (p < 0.001).  Source partitioning of N2O flux data revealed that soil organic matter nitrogen (SOM-N) was positively primed for N2O flux by the addition of urea fertilizer (p < 0.001), but positive SOM-N priming was reduced by an antagonistic interaction with artificial exudate application (p < 0.001). Further, examination of 15N-N2O site preference found that the main processes by which N2O is formed (nitrification and denitrification) were differentially process-primed by the addition or absence of ARE. Cumulative denitrification and nitrification contributions to total N2O flux were both positively primed in the soils receiving both ARE and urea inputs relative to a control (50.0 ± 10.1 and 28.2± 8.0 μg N2O-N kg-1, respectively). In soils receiving only ARE application, denitrification-derived N2O was negatively primed relative to a control and thus contributed less to overall N2O flux (-9.5 ± 12.4 μg N2O-N kg-1) but nitrification-derived N2O was positively primed (17.2 ± 9.0 μg N2O-N kg-1).

How to cite: Daly, E. and Hernandez Ramirez, G.: Source-process partitioning of soil N2O and CO2 production: nitrogen and simulated exudate additions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2221, https://doi.org/10.5194/egusphere-egu2020-2221, 2020

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