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| Titel |
Effect of organic fertilizer and biochar application on soil macro-aggregate formation and organic carbon turnover |
| VerfasserIn |
Dennis Grunwald, Michael Kaiser, Bernard Ludwig |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110764
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| Publikation (Nr.) |
 EGU/EGU2015-10799.pdf |
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| Zusammenfassung |
| Macro-aggregates are important for the organic matter dynamic and thus the productivity of
sustainably managed soils. To date, less is known about the influence of biochar in
comparison to other commonly used organic soil additives on the formation of
macro-aggregates and organic carbon turnover. Here we aimed to analyze the effects
of biochar applied individually and in combination with slurry versus the effects
of the individual application of slurry and manure on macro-aggregate yield, the
associated organic carbon concentration, and the organic carbon mineralization. For
this, we crushed the macro-aggregate fraction (>250 μm) of two different soils
that were then mixed with biochar (combustion temperature: 550Ë C, feedstock:
woodchips) and/or cattle-slurry or cattle-manure and incubated within a microcosm
experiment at 5Ë C, 15Ë C, and 25Ë C. We monitored the CO2 evolution during the
incubation experiment. After four and eight weeks, we determined the dry mass and the
carbon concentration of the newly formed macro-aggregates (>250 μm) and the
microbial biomass carbon concentration. Carbon mineralization was modelled assuming
first-order kinetics and using a rate modifying factor for the temperature (taken from
the RothC-26.3 model). Two pools were considered (mineralization of the native
organic matter from the control soils and mineralization of the substrates added) in
each treatment and the models were calibrated to the C mineralization data at 25Ë
C, whereas the data for 15Ë C and 5Ë C were used for validation. Independent
from the incubation temperature and the duration of the experiment, the individual
application of biochar did not show significant effects on the macro-aggregate yield, the
associated carbon concentration, or the CO2 emission rate compared to the control
sample receiving no amendments. For the application of biochar in combination with
slurry, we observed only for the 15Ë C treatment higher CO2 emission rates in
combination with higher macro-aggregate yields and microbial biomass carbon
concentrations compared to the control sample. Among the analyzed treatments,
the individual application of slurry resulted at 15Ë C in the largest increase in the
macro-aggregate yield and associated carbon concentration compared to the control sample.
However, this did not coincide with respective differences regarding the microbial
biomass and the CO2 emission rate. The CO2 emissions for the control and biochar
treatments were well estimated by the chosen model approach indicating a strong
positive temperature influence on the C mineralization kinetic. The CO2 emissions in
the treatments with application of slurry (with and without biochar) and manure
were well to satisfactorily described (25Ë C) and estimated (15Ë C and 5Ë C). No
adjustment of maximum mineralizable C amounts or rate constants were required at
the different temperatures, indicating the usefulness of the rate-modifying factor
for temperature for the different amendments. Our results further suggest that the
biochar studied here is only beneficial for soil macro-aggregate formation if applied
in combination with a further organic additive such as slurry. The formation of
macro-aggregates seems to be influenced by the temperature with the largest positive
effect observed here at 15Ë C compared to 5Ë C and 25Ë C incubation temperature. |
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