Sequential extractions and 31P-NMR spectroscopy of phosphorus forms in animal manures, whole soils and particle-size separates from a densely populated livestock area in northwest Germany |
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Authors: | P Leinweber L Haumaier W Zech |
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Institution: | (1) Institute for Structural Analysis and Planning in Areas of Intensive Agriculture, University of Vechta, Driverstrasse 22, PO Box 1553, D-49364 Vechta, Germany, DE;(2) Institute of Soil Science and Soil Geography, University of Bayreuth, D-95440 Bayreuth, Germany, DE;(3) Institute of Soil Science and Soil Geography, University of Bayreuth, D-95440 Bayreuth, Germany, DE |
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Abstract: | The solubility and forms of phosphorus (P) were investigated in manures from chicken and pigs, eight whole soil samples and
clay-, silt-, and sand-size separates from an arable and a grassland soil. Total P (Pt) in liquid pig manure (16.2 g kg–1) and dry chicken manure (26.2 g kg–1) was distributed between residual P (39–41% Pt), H2SO4–P (17–27% Pt), labile resin- and NaHCO3–P (24–39% Pt), and NaOH-P (3–10% Pt). Most soils had larger proportions of NaOH-P and residual P, indicating reactions of manure-derived P compounds with pedogenic
oxides and humic substances. Clay-size separates had the highest P-concentrations in all fractions and were particularly enriched
in exchangeable and labile P forms. Solution 31P-nuclear magnetic resonance (NMR) spectra of 0.5 M NaOH extracts from manures and some soil samples showed greater signal intensities for orthophosphate and monoester P than
0.1 M NaOH extracts. This can be explained by alkaline hydrolysis phosphate diesters at higher NaOH concentrations and/or by preferential
extraction of diesters at lower concentrations. The 31P-NMR spectra showed differences between the two manures and confirmed that increasing proportions of ester-P can be expected
if they are spread to soils. The NaOH extracts of soil samples were characterized by large proportions of orthophosphate-P
(mean 77% of assigned P compounds), which seemed to be slightly enriched in clay fractions whereas the extracts from silt
contained more ester-P. Sequential extractions and 31P-NMR spectroscopy both showed that these excessively manured soils are likely to lose large amounts of P.
Received: 15 July 1996 |
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Keywords: | Phosphorus forms P fractionations NMR spectroscopy Animal manures P esters Clay size separates |
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