Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions

P Quin; S Joseph; O Husson; S Donne; D Mitchell; P Munroe; D Phelan; A Cowie; L Van Zwieten

doi:10.1038/srep16773

Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions

Sci Rep. 2015 Nov 30:5:16773. doi: 10.1038/srep16773.

Authors

P Quin^{1

2}, S Joseph^{3

4

5}, O Husson⁶, S Donne⁴, D Mitchell⁷, P Munroe³, D Phelan⁸, A Cowie⁹, L Van Zwieten^{1

2

10}

Affiliations

¹ University of New England, Armidale, NSW 2351, Australia.
² Wollongbar Primary Industries Institute, NSW Department of Primary Industries, 1243 Bruxner Highway, Wollongbar, NSW 2477, Australia.
³ School of Materials Science and Engineering, University of New South Wales, NSW 2052, Australia.
⁴ Discipline of Chemistry, University of Newcastle, Callaghan NSW 2308, Australia.
⁵ Department of Physics and Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong NSW, 2522, Australia.
⁶ CIRAD, UPR AIDA, TAB 115/02 Avenue Agropolis 34398 Montpellier Cedex 5, France and AfricaRice Centre, 01 BP 2031 Cotonou, Bénin.
⁷ Electron Microscopy Center, AIIM, University of Wollongong, Wollongong NSW, 2522, Australia.
⁸ Electron Microscope and X-Ray Unit, University of Newcastle, Callaghan NSW 2308, Australia.
⁹ NSW Department of Primary Industries, University of New England, Armidale, NSW 2351, Australia.
¹⁰ Southern Cross Plant Science, Southern Cross University, Military Road, East Lismore NSW 2480, Australia.

Abstract

Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C)--0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS)--in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.