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| Titel |
Effects of biogas digestate and cattle slurry application on greenhouse gas emissions from grasslands on organic soils |
| VerfasserIn |
Tim Eickenscheidt, Annette Freibauer, Jan Heinichen, Jürgen Augustin, Matthias Drösler |
| 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 |
250095025
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| Publikation (Nr.) |
 EGU/EGU2014-10465.pdf |
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| Zusammenfassung |
| The change in the German energy policy resulted in a strong development of biogas plants in
Germany. As a consequence, drained peatlands are increasingly used to satisfy the rising
demand for fermentative substrates. In return high amounts of nutrient-rich digestates are
used as organic fertilizer to maintain soil fertility and crop yield. It is well known
that organic fertilization enhances nitrous oxide (N2O) emissions from managed
grasslands, especially in south Germany, a region with frequently frost-thaw cycles.
Additionally drained organic soils are considered as hotspots of GHG emissions including
N2O.
Our study addressed the question to what extent biogas digestate and cattle slurry
application alters N2O and methane (CH4) fluxes and how different contents of soil organic
matter (SOM) promote the production of GHG. The study was conducted at two areas within
one grassland parcel, which differed in their soil organic carbon (SOC) contents (10% versus
17%). At each area (named Corg medium and Corg high) three sites were established: One
was fertilized five times with biogas digestate, the second five times with cattle slurry
and the third site served as control without fertilization. For each treatment, the
fluxes of N2O and CH4 were measured over two years using the closed chamber
method.
Significantly higher short term (16 days) N2O fluxes after fertilization with digestate
compared to slurry could only be found in one out of four fertilisation events. However, on an
annual basis the application of biogas digestate significantly enhanced the N2O fluxes
compared to the application of cattle slurry. Furthermore, N2O fluxes from the Corghigh site
significantly exceeded N2O fluxes from the Corg medium sites. Annual cumulative emissions
ranged from 0.91 ± 0.49 kg N ha-1 yr-1 to 3.14 ± 0.91 kg N ha-1 yr-1, reflecting the lower
end of literature values from other organic soils and corresponding more to those reported
from grasslands on mineral soils in Germany. Significantly different CH4 fluxes
between the investigated treatments or the different soil types were not observed.
Cumulative annual CH4 exchange rates varied between -0.21 ± 0.19 kg C ha-1 yr-1 and
-1.06 ± 0.46 kg C ha-1 yr-1, confirming the minor importance of CH4 emissions
from applied organic fertilizers for the GHG balance of agricultural grasslands.
It could be shown that the frequent but low dosage application of fertilizer and
quick N uptake by plants avoid conditions favourable for high N2O emissions.
However, the observed linear increase of 16 days cumulative N2O-N exchange or
rather annual N2O emissions, due to a higher mean groundwater level and a higher
application rate of NH4+-N, reveal the importance of site adapted N fertilization and
the avoidance of N surpluses during the agricultural use of Corg rich grasslands. |
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