Web Release Date: December 19,
Direct Speciation of Phosphorus in Alum-Amended Poultry Litter: Solid-State 31P NMR Investigation
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School of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, and Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware 19717
Received for review July 12, 2003
Revised manuscript received November 4, 2003
Accepted November 10, 2003
Abstract:
Amending poultry litter (PL) with aluminum sulfate (alum) has proven to be effective in reducing water-soluble phosphorus (P) in the litter and in runoff from fields that have received PL applications; it has therefore been suggested as a best management practice. Although its effectiveness has been demonstrated on a macroscopic scale in the field, little is known about P speciation in either alum-amended or unamended litter. This knowledge is important for the evaluation of the long-term stability and bioavailability of P, which is a necessary prerequisite for the assessment of the sustainability of intensive poultry operations. Both solid-state MAS and CP-MAS 31P NMR as well as 31P{27Al}TRAPDOR were used to investigate P speciation in alum-amended and unamended PL. The results indicate the presence of a complex mixture of organic and inorganic orthophosphate phases. A calcium phosphate phase, probably a surface precipitate on calcium carbonate, could be identified in both unamended and alum-amended PL, as well as physically bound HPO42-. Phosphate associated with Al was found in the alum-amended PL, most probably a mixture of a poorly ordered wavellite and phosphate surface complexes on aluminum hydroxide that had been formed by the hydrolysis of alum. However, a complex mixture of organic and inorganic phosphate species could not be resolved. Phosphate associated with Al comprised on average 40 ± 14% of the total P in alum-amended PL, whereas calcium phosphate phases comprised on average 7 ± 4% in the alum-amended PL and 14 ± 5% in the unamended PL.
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