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| Titel |
Denitrification ‘hot spots' in soil following surface residue application |
| VerfasserIn |
Marianne Kuntz, Nicholas J. Morley, Paul D. Hallett, Christine Watson, Elizabeth M. Baggs |
| 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 |
250101726
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| Publikation (Nr.) |
 EGU/EGU2015-918.pdf |
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| Zusammenfassung |
| The availability of organic C is an important driver for the production and reduction of the
greenhouse gas nitrous oxide (N2O) during denitrification. Denitrification as a response to
plant residue amendments to soil surfaces has been extensively researched. However, the
nature of hotspot sites of N2O production and reduction within the soil profile, especially in
relation to the location of applied residues, is unknown. In a laboratory experiment we
investigated the relationship between denitrifier N2O surface fluxes and N2O production and
reduction sites. Probes which equilibrate with the soil gas phase by diffusion were developed
to quantify denitrification products and product ratios at 1-2 cm, 4.5-5.5 cm or 8-9 cm from
the surface. 13C labelled barley straw was incorporated at rates of 0, 2 and 4 t ha-1
into the top 3 cm of soil and subsequently amended with 14NH415NO3. In a three
week experiment the soil gas phase at the three depths was analysed for 15N-N2O,
15N-N2, 13C-CO2 and O2 concentrations. Additionally, cores were destructively
sampled for mineral 15N as well as microbial C and dissolved C in the respective
depths.
15N-N2O and CO2 surface fluxes peaked one day after N application, with residue
application resulting in significantly higher 15N-N2O emission rates compared to the
non-amended control. The timing of the 15N-N2O surface flux on day 1 was related to
maximum 15N-N2O concentrations of 36.6 μg 15N L-1 within the pore space at 5 cm
depth. Three days after fertilizer application 15N-N2O pore space concentrations
had significantly increased to 193 μg 15N L-1 at 9 cm depth indicating denitrifier
activity at greater depth. Denitrification below the soil surface could be explained by
increased microbial activity, oxygen depletion with increasing depth and progressive
downwards diffusion of fertilizer NO3-. However, C availability appeared to only
affect denitrification in the surface layer in which the residue was incorporated.
Our results provide insight into the nature and drivers of ‘hotspots’ of denitrifier
activity within the soil profile. Such information can contribute to the development of
sustainable management practices that lower net emissions of N2O from arable soils. |
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