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| Titel |
Characterization of extractable soil organic matter pools from African Dark Earths (AfDE): A case study in historical biochar and organic waste amendments |
| VerfasserIn |
Manna Fujiu, Alain Plante, Tsutomu Ohno, Dawit Solomon, Joh. Lehmann, James Fraser, Melissa Leach, James Fairhead |
| 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 |
250097320
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| Publikation (Nr.) |
 EGU/EGU2014-12886.pdf |
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| Zusammenfassung |
| Anthropogenic Dark Earths are soils generated through long-term human inputs
of organic and pyrogenic materials. These soils were originally discovered in the
Amazon, and have since been found in Australia and in this case in Africa. African
Dark Earths (AfDE) are black, highly fertile and carbon-rich soils that were formed
from the original highly-weathered infertile yellowish to red Oxisols and Ultisols
through an extant but hitherto overlooked climate-smart sustainable soil management
system that has long been an important feature of the indigenous West African
agricultural repertoire. Studies have demonstrated that ADE soils in general have
significantly different organic matter properties compared to adjacent non-DE soils,
largely attributable to the presence of high concentrations of ash-derived carbon.
Quantification and characterization of bulk soil organic matter of several (n=11) AfDE
and non-AfDE pairs of surface (0-15 cm) soils using thermal analysis techniques
(TG-DSC-EGA) confirmed substantial differences in SOM composition and the presence of
pyrogenic C. Such pyrogenic organic matter is generally considered recalcitrant or
relatively stable, but the goal of the current study was to characterize the presumably
labile, more rapidly cycling, pools of C in AfDEs through the characterization of hot
water- and pyrophosphate-extractable fractions, referred to as HWEOC and PyroC
respectively. Extracts were analyzed for carbon content, as well as composition using
fluorescence (EEM/PARAFAC) and high resolution mass spectrometry (FTICR-MS).
The amount of extractable C as a proportion of total soil C was relatively low: less
than ~0.8% for HWEOC and 2.8% for PyroC. The proportion of HWEOC did not
differ (P = 0.18, paired t-test) between the AfDE and the non-AfDE soils, while
the proportions of PyroC were significantly larger (P = 0.001) in the AfDE soils
compared to the non-AfDE soils. Preliminary analysis of the EEM/PARAFAC data
suggests that AfDE samples had a greater fraction of their DOM that was more
humic-like than the paired non-AfDE samples, though differences were small. Similarly,
FTICR-MS analysis of hot water extracts suggests that differences among the three sites
analyzed were larger than between the paired AfDE and non-AfDE extracts. Overall, in
spite of substantial differences in the composition of bulk SOM, the extractable
fractions appear to be relatively similar between the AfDE and non-AfDE soils. |
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