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| Titel |
Measuring denitrification after grassland renewal and grassland conversion to cropland by using the 15N gas-flux method |
| VerfasserIn |
Caroline Buchen, Wolfram Eschenbach, Heinz Flessa, Anette Giesemann, Dominika Lewicka-Szczebak, Reinhard Well |
| 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 |
250106341
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| Publikation (Nr.) |
 EGU/EGU2015-6006.pdf |
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| Zusammenfassung |
| Denitrification, the reduction of oxidized forms of inorganic N to N2O and N2 is an important
pathway of gaseous nitrogen losses. Measuring denitrification, especially the reduction of
N2O to N2, expressed in the product ratio (N2O/(N2O + N2)), is rather difficult and hence
rarely performed under field conditions. But using the 15N gas-flux method allows
determining N transformation processes in their natural environment. In order to
develop effective climate mitigation strategies understanding the N2O source is
essential.
We used the 15N gas-flux method to determine N2O and N2 emissions following
grassland renewal and conversion techniques. Therefore we selected three different
treatments: control (C), mechanical grassland renovation (GR) (autumn 2013) and grassland
conversion to maize (GM) (spring 2014) from field plot trials on two different sites (Histic
Gleysoil and Plaggic Anthrosol) near Oldenburg, Lower Saxony, Germany. We applied
15N labeled KNO3- (60 atom. % 15N) at a rate equivalent to common farming
practices (150 kg N*ha-1) using needle injection of fertilizer solution in three
different depths (10 cm, 15 cm, 20 cm) for homogeneous soil labeling up to 30
cm in microplots. During the first 10 days after application (May 2014) gas flux
measurements from closed chambers were performed every second day and then weekly
following a period of 8 weeks. Gas samples were analyzed for δ15N of N2 and N2O
by IRMS according to Lewicka-Szczebak et al. (2013). Concentration and 15N
enrichment of NO3- in soil water was determined on weekly samples using the
SPIN-MAS technique (Stange et al. 2007). Fluxes of N2 and N2O evolved from the
15N labeled soil nitrogen pool were calculated using the equations of Spott et al.
(2006).
Peak events of N2 and N2O emissions occurred during the first 10 days of measurement,
showing differences in soil types, as well as treatment variations. N2 fluxes up to 178
g*ha-1*day-1 and N2O fluxes up to 280 g*ha-1*day-1 were measured on the Plaggic
Anthrosol in the GR treatment, while on the Histic Gleysoil, the GM treatment showed
highest fluxes with N2 fluxes up to 1260 g*ha-1*day-1 and N2O fluxes up to 747
g*ha-1*day-1. Alike the product ratio of initial fluxes was higher on the Plaggic Anthrosol
and lower on the Histic Gleysoil. Data analysis is still in progress and further results will be
provided.
References:
Lewicka-Szczebak, D., R. Well, A. Giesemann, L. Rohe and U. Wolf (2013). "An
enhanced technique for automated determination of 15N signatures of N2, (N2+N2O)
and N2O in gas samples." Rapid Communications in Mass Spectrometry 27(13):
1548-1558.
Spott, O., R. Russow, B. Apelt and C. F. Stange (2006). "A 15N-aided artificial
atmosphere gas flow technique for online determination of soil N2 release using the
zeolite Köstrolith SX6®." Rapid Communications in Mass Spectrometry 20(22):
3267-3274.
Stange, F., O. Spott, B. Apelt and R. W. Russow (2007). "Automated and rapid online
determination of 15N abundance and concentration of ammonium, nitrite, or nitrate in
aqueous samples by the SPINMAS technique." Isotopes in Environmental and Health Studies
43(3): 227-236. |
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