Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil

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 i...

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Main Authors: X. Jiang, R. Bol, S. Willbold, H. Vereecken, E. Klumpp
Format: Article
Language:English
Published: Copernicus Publications 2015-11-01
Series:Biogeosciences
Online Access:http://www.biogeosciences.net/12/6443/2015/bg-12-6443-2015.pdf
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author X. Jiang
R. Bol
S. Willbold
H. Vereecken
E. Klumpp
author_facet X. Jiang
R. Bol
S. Willbold
H. Vereecken
E. Klumpp
author_sort X. Jiang
collection DOAJ
description 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–Na<sub>2</sub>EDTA) extraction with solution <sup>31</sup>P-nuclear magnetic resonance (<sup>31</sup>P-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 <sup>31</sup>P-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. <br><br> 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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spelling doaj.art-9ff82bce5bf246cb86b5cca305505aaf2022-12-21T19:14:09ZengCopernicus PublicationsBiogeosciences1726-41701726-41892015-11-0112216443645210.5194/bg-12-6443-2015Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soilX. Jiang0R. Bol1S. Willbold2H. Vereecken3E. Klumpp4Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Jülich, GermanyInstitute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Jülich, GermanyCentral Institute for Engineering, Electronics and Analytics, Analytics (ZEA-3), Forschungszentrum Jülich GmbH, Wilhelm Johnen Straße, 52425 Jülich, GermanyInstitute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Jülich, GermanyInstitute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Jülich, GermanyTo 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–Na<sub>2</sub>EDTA) extraction with solution <sup>31</sup>P-nuclear magnetic resonance (<sup>31</sup>P-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 <sup>31</sup>P-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. <br><br> 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.http://www.biogeosciences.net/12/6443/2015/bg-12-6443-2015.pdf
spellingShingle X. Jiang
R. Bol
S. Willbold
H. Vereecken
E. Klumpp
Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
Biogeosciences
title Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
title_full Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
title_fullStr Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
title_full_unstemmed Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
title_short Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
title_sort speciation and distribution of p associated with fe and al oxides in aggregate sized fraction of an arable soil
url http://www.biogeosciences.net/12/6443/2015/bg-12-6443-2015.pdf
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