Stoichiometric ratio of dissolved organic carbon to nitrate regulates nitrous oxide emission from the biochar-amended soils

Z M Lan; C R Chen; M Rezaei Rashti; H Yang; D K Zhang

doi:10.1016/j.scitotenv.2016.10.119

Stoichiometric ratio of dissolved organic carbon to nitrate regulates nitrous oxide emission from the biochar-amended soils

Sci Total Environ. 2017 Jan 15:576:559-571. doi: 10.1016/j.scitotenv.2016.10.119. Epub 2016 Oct 27.

Authors

Z M Lan¹, C R Chen², M Rezaei Rashti³, H Yang⁴, D K Zhang⁴

Affiliations

¹ Australian Rivers Institute, Griffith School of Environment, Griffith University, Nathan, QLD 4111, Australia; Soil and Fertilizer Institute, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China.
² Australian Rivers Institute, Griffith School of Environment, Griffith University, Nathan, QLD 4111, Australia. Electronic address: c.chen@griffith.edu.au.
³ Australian Rivers Institute, Griffith School of Environment, Griffith University, Nathan, QLD 4111, Australia.
⁴ Centre for Energy (M473), School of Mechanical and Chemical Engineering (M050), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.

PMID: 27810745
DOI: 10.1016/j.scitotenv.2016.10.119

Abstract

Biochar has the potential to mitigate nitrous oxide (N₂O) emissions from soils. However, the mechanisms responsible for N₂O emission in biochar-amended soils are yet to be elucidated. In this study, an incubation experiment was carried out to investigate the effects of seven biochars (eucalyptus, softwood mixture, mallee, jarrah, peanut shell, green waste and radiata pine) on the stoichiometric shifts of dissolved organic carbon (DOC), nitrate (NO₃^--N) and N₂O emission in two contrasting soils (Ferrosol with 5.3% total C, 0.46% total N; Tenosol with 0.4% total C, 0.01% total N). All biochar treatments were found to significantly reduce N₂O emission in Tenosol by 61-72%. However, in Ferrosol, biochars' impacts on N₂O emission were variable, with only peanut shell, green waste and radiata pine bicohars significantly reducing N₂O emission by 17-23%. A decrease in NO₃^- availability in most biochar-amended treatments also was observed in both soils compared with the control. The N₂O fluxes in Ferrosol were mainly regulated by the shifts in the availability and stoichiometry of DOC and NO₃^- induced by the biochar amendments. The DOC derived from biochars increased DOC:NO₃^- ratio in Ferrosol at the beginning of the experiment, but these effects disappeared 7days after incubation. Overall, the N₂O fluxes were C-limited due to the presence of high concentrations of NO₃^- in Ferrosol. However, in Tenosol, the relationship between stoichiometry of DOC:NO₃^- and N₂O fluxes was much weaker than Ferrosol and N₂O fluxes mainly limited by the concentration of NO₃^-. This study demonstrated that the mechanisms responsible for biochar effects on soil N₂O fluxes are considered to be soil and biochar specific.

Keywords: Biochar; Denitrification; Dissolved organic C; Nitrate; Nitrous oxide; Stoichiometry.