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| Titel |
Emissions of N2O from organic soils managed by agriculture in North Western Denmark (Possible production and reduction spots) |
| VerfasserIn |
Arezoo Taghizadeh-Toosi, Lars Elsgaard, Vibeke Ernstsen, Tim J. Clough, Søren O. Petersen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250153189
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| Publikation (Nr.) |
 EGU/EGU2017-18134.pdf |
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| Zusammenfassung |
| In North Western Denmark, organic soils are extensively under agricultural management for
cereal and high-value cash crop production or as grazing land. The area (overlying raised
seabed) has been classified as potentially acid sulfate soil. Drainage and tillage of organic soil
is known to promote emissions of nitrous oxide (N2O), but a previous monitoring program
found annual N2O emissions from adjacent fields with rotational grass and potato that were,
respectively, 3 and 5 times higher than default values proposed by The Intergovernmental
Panel on Climate Change (IPCC, 2014). In order to study underlying mechanisms, the same
two sites and two new reference sites along an East-West transect were investigated during
2015.
The four sites (i.e. two with rotational grass and two sites with a potato crop)
were equipped for weekly monitoring of soil surface N2O emissions and sub-soil
N2O concentrations to 1 m depth during spring and autumn 2015. Also, various
environmental variables (precipitation, air and soil temperature, soil moisture, groundwater
level, and soil mineral N) were monitored. In April and August 2015, intact cores
to 1 m depth were collected at the paired grassland and potato sites and analysed
for pH, EC, nitrite, reactive Fe, acid volatile S (AVS) and chromium-reducible S
(CRS).
Nitrous oxide concentrations in the soil profile showed strong temporal dynamics
reflecting water table changes, as well as precipitation and in some cases fertilization.
At the paired site concentrations in the potato field (reaching 2000 μL N2O L−1)
were much higher than in the adjacent grassland (up to 20 μL N2O L−1). Soil pH
averaged 4.9 at the two paired sites. The difference was confirmed at reference sites.
Accumulated emissions of N2O during monitoring periods (in total 151-174 d)
corresponded to 18 and 48 kg N ha−1 at potato sites, but only 3 and 4 kg N ha−1 at the
grassland sites. Nitrous oxide accumulated at depth in the soil during phases of
declining water table in spring, but also when the water table raised to near the
surface due to precipitation. On several occasions N2O also accumulated at shallow
depth, and with elevated emissions, in connection with rainfall. Total reactive iron
and sulfur content, including AVS and CRS, showed great heterogeneity in the
profiles of both grassland and potato fields, and no clear relationships have been
found between reactive iron or sulfur compounds and N2O concentrations in soil
profile. However, controlled incubation experiments are on-going to identify possible
mechanisms behind the accumulation and extremely high emissions of N2O from
potato fields, especially whether acidifying processes can be linked to soil nitrate or
nitrite reduction (e.g., through oxidation of ferrous iron to ferric iron, and sulfide to
sulfate).
Key words: Acid sulfate soils, organic soils, agricultural management, nitrous oxide
emissions, environmental variables |
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