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| Titel |
Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil |
| VerfasserIn |
X. Jiang, R. Bol, S. Willbold, H. Vereecken, E. Klumpp |
| 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 ; 12, no. 21 ; Nr. 12, no. 21 (2015-11-11), S.6443-6452 |
| Datensatznummer |
250118160
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| Publikation (Nr.) |
 copernicus.org/bg-12-6443-2015.pdf |
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| Zusammenfassung |
To maximize crop productivity fertilizer P is generally applied to arable
soils, a significant proportion of which becomes stabilized by mineral
components and in part subsequently becomes unavailable to plants. However,
little is known about the relative contributions of the different organic
and inorganic P bound to Fe/Al oxides in the smaller soil particles. Alkaline (NaOH–Na2EDTA) extraction with solution 31P-nuclear
magnetic resonance (31P-NMR) spectroscopy is considered a reliable
method for extracting and quantifying organic P and (some) inorganic P.
However, any so-called residual P after the alkaline extraction has remained
unidentified. Therefore, in the present study, the amorphous (a) and
crystalline (c) Fe/Al oxide minerals and related P in soil aggregate-sized
fractions (> 20, 2–20, 0.45–2 and < 0.45 μm) were
specifically extracted by oxalate (a-Fe/Al oxides) and dithionite–citrate–bicarbonate (DCB, both
a- and c-Fe/Al oxides). These soil aggregate-sized fractions with and
without the oxalate and DCB pre-treatments were then sequentially extracted
by alkaline extraction prior to solution 31P-NMR spectroscopy. This was
done to quantify the P associated with a- and c-Fe/Al oxides in both
alkaline extraction and the residual P of different soil aggregate-sized
fractions.
The results showed that overall P contents increased with decreasing size of
the soil aggregate-sized fractions. However, the relative distribution and
speciation of varying P forms were found to be independent of soil
aggregate-size. The majority of alkaline-extractable P was in the a-Fe/Al
oxide fraction (42–47 % of total P), most of which was ortho-phosphate
(36–41 % of total P). Furthermore, still significant amounts of
particularly monoester P were bound to these oxides. Intriguingly, however,
Fe/Al oxides were not the main bonding sites for pyrophosphate. Residual P
contained similar amounts of total P associated with both a- (11–15 % of
total P) and c-Fe oxides (7–13 % of total P) in various aggregate-sized
fractions, suggesting that it was likely occluded within the a- and c-Fe
oxides in soil. This implies that, with the dissolution of Fe oxides, this P
may be released and thus available for plants and microbial communities. |
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