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| Titel |
Biochar carbon sequestration and downward translocation in contrasting soils under field conditions in Australia |
| VerfasserIn |
Bhupinder Pal Singh, Yunying Fang, Mark Boersma, Pushpinder Matta, Lukas Van Zwieten, Lynne Macdonald |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100348
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| Publikation (Nr.) |
 EGU/EGU2014-16287.pdf |
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| Zusammenfassung |
| Carbon (C) sequestration potential of biochar depends on its stability and stabilisation of
native or added organic C in soil. However, the processes of biochar degradation, fate
in soil organic matter pools, and downward translocation in the soil profile, and
the influence of biochar on emissions or stabilisation of native organic C sources
are poorly understood under field conditions. An Eucalyptus saligna green-waste
biochar (δ13C -36.6o; total C 66.8%) produced by slow pyrolysis at 450° C was
applied at 29.2 t ha-1 to 10-cm depth in circular (0.66-m diameter) micro-plots,
encompassing three soils [Tenosol, Dermosol and Ferrosol (Australian Soil Classification);
Arenosol, Planosol, Ferralsol (approximate WRB Classification] under contrasting
pasture systems across New South Wales and Tasmania (Australia). The aims of this
study were to (i) monitor the fate of biochar C in respired CO2 and quantify biochar
stability and stabilisation under field conditions, (ii) determine the influence of
biochar on native soil C emissions, and (iii) track downward migration of the surface
(0-10 cm) applied biochar over a 1-year period. We also periodically monitored the
impact of biochar on microbial biomass carbon (MBC) and aboveground biomass
production. The soils were separated into light and heavy C fractions and the C
recovery of applied biochar C was calculated at 0-8, 8-12, 12-20 and 20-30 cm
depths.
Biochar C mineralisation rates were generally higher, albeit fluctuated widely, in the first
3 to 4 months. Over the first 7 months, the proportion of added biochar C mineralised in soils
ranged between 1.4 and 5.5% and followed the sequence: Tenosol < Dermosol < Ferrosol.
The mean residence time (MRT) of biochar ranged from 29 and 70 years. These
values of MRT should be treated as highly conservative values, as they mainly
reflect the MRT of relatively labile C components in biochar. The cumulative CO2-C
emission over the 7-month period from native soil and plant sources was larger in
the biochar-amended Tenosol, whereas lower in the biochar-amended Dermosol
and Ferrosol, relative to the corresponding controls. As the aboveground biomass
production was similar between the biochar-amended and control micro-plots during
the first 7 months, the higher cumulative CO2-C emission in the biochar versus
control Tenosol may be related to positive priming of native SOC mineralisation by
biochar, and/or greater belowground allocation of plant-assimilated C, or possibly
alternative effects (i.e. negative priming or lower belowground plant C allocation) in the
Dermosol and Ferrosol. At 4 months, most of the applied biochar was recovered in the
top 12 cm depth, with the total recovery of 72.1% in the Tenosol, 103.7% in the
Dermosol and 79.2% in the Ferrosol. Biochar C was clearly migrated downward
from the application depth (0-10 cm) within 4 months, particularly in Tenosol and
Ferrosol, with the recovery of 4.8%, 2.7% and 12.7% in the 12-20 cm profile,
and 6.0%, 1.1% and 9.1% at the 20-30 cm profile, across the Tenosol, Dermosol
and Ferrosol, respectively. At 4 months, MBC was higher in the biochar-amended
Tenosol and Dermosol than the corresponding controls, whereas, biochar had no
effect on MBC in the Ferrosol, possibly due to its higher native organic C content
cf. the other soil types. The updated results will be presented at the conference. |
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