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| Titel |
Subcritical water extraction to isolate kinetically different soil nitrogen fractions |
| VerfasserIn |
S. Sleutel, M. A. Kader, K. Demeestere, C. Walgraeve, J. Dewulf, S. Neve |
| 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 ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-19), S.7435-7447 |
| Datensatznummer |
250085425
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| Publikation (Nr.) |
 copernicus.org/bg-10-7435-2013.pdf |
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| Zusammenfassung |
| Soil organic N is largely composed of inherently biologically labile
proteinaceous N and its persistence in soil is mainly explained by
stabilization through binding to minerals and other soil organic matter (SOM)
components at varying strengths. In order to separate kinetically different
soil N fractions we hypothesize that an approach which isolates soil N
fractions on the basis of bonding strength is required, rather than employing
chemical agents or physical methods. We developed a sequential subcritical
water extraction (SCWE) procedure at 100, 150 and 200 °C to isolate
SOM fractions. We assessed these SCWE N fractions as predictors for aerobic
and anaerobic N mineralization measured from 25 paddy soil cores in
incubations. SCWE organic carbon (SCWE OC) and N (SCWE N) increased
exponentially with the increase of temperature and N was extracted
preferentially over OC. The efficiency of SCWE and the selectivity towards N
were both lower in soils with increasingly reactive clay mineralogy. Stepwise
linear regression found no relations between the SCWE fractions and the
anaerobic N mineralization rate but instead with pH and a model parameter
describing the temperature dependency of SCWE extraction. Both were linked to
texture, mineralogy and content of pedogenic oxides, which suggests an
indirect relation between anaerobic NH4+ release and these edaphic
soil factors. N mineralization appeared to be largely decoupled from SOM
quantity and quality. From the present study on young paddy soils low in
pedogenic oxides and with high fixed NH4+ content we cannot infer the
performance of SCWE to isolate bio-available N in more developed upland
soils. There may be potential to separate kinetically different SOM pools
from upland soils because 1° for aerobic N mineralization at
100–150 °C SCWE N was the best predictor; and 2° SCWE
selectively extracted N over C and this preference depended on the
mineralogical composition. Hence N fractions differing in bonding strength
with minerals or SOM might be isolated at different temperatures, and
specifically this association has frequently been found a prominent
stabilization mechanism of N in temperate region cropland soils. |
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