The influence of above-ground residue input and incorporation on GHG fluxes and stable SOM formation in a sandy soil

Mitchell, Elaine, Scheer, Clemens, Rowlings, David W., Conant, Richard T., Cotrufo, M. Francesca, van Delden, Lona, & Grace, Peter R. (2016) The influence of above-ground residue input and incorporation on GHG fluxes and stable SOM formation in a sandy soil. Soil Biology and Biochemistry, 101, pp. 104-113.

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Abstract

Carbon sequestration in agricultural soils has been promoted as a means to reduce atmospheric concentrations of greenhouse gases (GHG) whilst improving soil productivity. Although there is broad agreement on practices that increase carbon (C) stocks, there is a lack of understanding on the stability of these gains and how changes in soil organic carbon (SOC) pools can influence GHG fluxes. We tracked the fate of above-ground residues into functionally different SOC pools and GHG fluxes using isotopically labelled residues (13C and 15N) over 12 months in a pasture soil in sub-tropical Australia. Agricultural residue management was simulated by: (1) altering the rate of residue input and, (2) mixing residue with topsoil. GHG fluxes were significantly greater at high residue input levels due to the priming of existing SOC and elevated N2O losses, fuelled by a greater availability of labile substrate. There was evidence of an asymptotic relationship between C input and residue-derived C accumulation in stable soil C pools at higher input levels, indicating that the soil was reaching its protective capacity. Mixing of residues contributed to a 40% increase in GHG fluxes in comparison to surface applied treatment, most notably from residue-derived C and N. This can be attributed to (i) the physical disruption of soil, particularly that of aggregates, which changed the microenvironment stimulating microbial activity, and (ii) greater residue-soil contact. Greater residue-soil contact through mixing also contributed to a 2 fold increase in the residue-derived C recovered in the mineral soil with the majority (56%) in the active C pool. Over a 12 month period, C sequestration was outweighed by GHG fluxes at high rates of input and when residues were mixed with the topsoil. C sequestration policies and associated management approaches must be assessed holistically under a range of conditions and in the long-term to ensure that detrimental practices are not promoted.

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ID Code: 98681
Item Type: Journal Article
Refereed: Yes
Keywords: Decomposition; Isotopes; Stable SOM; GHG fluxes; Agricultural residue management
DOI: 10.1016/j.soilbio.2016.07.008
ISSN: 0038-0717
Divisions: Current > Schools > School of Earth, Environmental & Biological Sciences
Past > QUT Faculties & Divisions > Faculty of Science and Technology
Current > Institutes > Institute for Future Environments
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2016 Elsevier Ltd.
Deposited On: 07 Sep 2016 01:28
Last Modified: 07 Sep 2016 22:25

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