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a Dep. of Earth and Environment, Univ. of Leeds, Leeds LS2 9JT, UK
b Dep. of Plant and Soil Sciences, Univ. of Delaware, 152 Townsend Hall, Newark, DE 19711
* Corresponding author (s.hunger{at}earth.leeds.ac.uk).
Received for publication June 21, 2007.
The use of spectroscopic techniques (especially phosphorus-31 nuclear magnetic resonance [31P-NMR] and X-ray absorption near edge structure spectroscopy) has recently advanced the analysis of the speciation of P in poultry litter (PL) and greatly enhanced our understanding of changes in P pools in PL that receive alum (aluminum sulfate) to reduce water-soluble P and control ammonia emissions from poultry houses. Questions remain concerning changes of P species during long-term storage, drying, or after application of PL to cropland or for other uses, such as turfgrass. In this study, we investigated a set of six PL samples (of which three were alum-amended and three were unamended) that had been characterized previously. The P speciation was analyzed using solid-state 31P-NMR spectroscopy, and the mineralogy was analyzed by powder X-ray diffraction (XRD) after storing the samples moist and dried for up to 5 yr under controlled conditions. The magnesium ammonium phosphate mineral struvite was identified in all but one PL samples. Struvite concentrations were generally lower in dried samples (
14%) than in samples stored moist (23 and 26%). The moist samples also had higher concentrations of phosphate bound to aluminum hydroxides. Solid-state NMR spectroscopy was in general more sensitive than XRD in detecting and quantifying P species. Although phosphate associated with calcium and aluminum made up a large proportion of P species, they were not detected by XRD.
Abbreviations: CP-MAS, cross-polarization, magic angle spinning DCP, dicalcium phosphate DI, deionized HAP, hydroxyapatite MAS, magic angle spinning NMR, nuclear magnetic resonance OCP, octacalcium phosphate PL, poultry litter TCP, tricalcium phosphate XANES, x-ray absorption near edge structure XRD, X-ray diffraction
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