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| Titel |
Measuring and modelling seasonal variation of gross nitrification rates in response to long-term fertilisation |
| VerfasserIn |
C. F. Stange, H.-U. Neue |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 10 ; Nr. 6, no. 10 (2009-10-14), S.2181-2192 |
| Datensatznummer |
250004038
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| Publikation (Nr.) |
 copernicus.org/bg-6-2181-2009.pdf |
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| Zusammenfassung |
The formation of nitrate (nitrification) in soils is an important process
that influences N availability for plant uptake and potential N losses as
well. Gross nitrification is an effective measure by which to test
mechanistic ecosystem models for predictability because gross rates can
widely differ between sites, even if net production is similar between these
sites.
A field experiment was designed to (i) determine gross nitrification rates
in response to fertilisation and (ii) to verify the idea that seasonal
variations of gross rates in soils can be readily predicted by soil moisture
and soil temperature.
Gross nitrification rates were measured by a Barometric Process Separation
(BaPS). The BaPS measurements were validated with the commonly used 15N
pool dilution technique measurements at six times. In general, the rates
determined from both measurement approaches were in the same order of
magnitude and showed a good correlation.
The effects of 100 years of fertilisation (mineral fertiliser, manure and
control) on gross nitrification rates were investigated. During 2004 soil
samples from the long-term "static fertilisation experiment" at Bad
Lauchstädt were sampled weekly and were measured in the laboratory under
field conditions and subsequently under standardised conditions (16°C
soil temperature and −30 kPa matrix potential) with the BaPS system. Gross
nitrification rates determined under standardised conditions did not show
any seasonal trend but did, however, reveal a high temporal variability.
Gross nitrification rates determined by the BaPS-method under field
conditions showed also a high temporal variability and ranged from 5 to 77 μg N h−1 kg−1
dry mass, 2 to 74 μg N h−1 kg−1
dry mass and 0 to 49 μg N h−1 kg−1 dry mass with respect to
manure, mineral fertiliser, and control. The annual average was 0.34, 0.27
and 0.19 g N a−1 kg−1 dry mass for the manure site, mineral
fertiliser site and control site, respectively. On all sites gross
nitrification revealed a strong seasonal dynamic. Three different models
were applied for reproducing the measured results. Test models could explain
75% to 78% of variability at the manure site, 66% to 77% of
variability at the mineral fertiliser site, and 39% to 63% of
variability at the control site. The model parameterisation shows that the
temperature sensitivity of gross nitrification differs between the three
neighbouring sites. Hence, a temperature response function in an ecosystem
model has to consider the site specificity in order to adequately predict
the effects of future climate change on the soil N cycle. |
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