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This article in JEQ

  1. Vol. 34 No. 2, p. 687-697
     
    Received: July 16, 2004
    Published: Mar, 2005


    * Corresponding author(s): gurpal@udel.edu
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doi:10.2134/jeq2005.0687

Phosphorus Speciation in Broiler Litter and Turkey Manure Produced from Modified Diets

  1. Gurpal S. Toor *a,
  2. J. Derek Peakb and
  3. J. Thomas Simsa
  1. a Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716
    b Department of Soil Science, University of Saskatchewan, Saskatoon, Canada S7N 5A8

Abstract

Modifying poultry diets by reducing mineral P supplementation and/or adding phytase may change the chemical composition of P in manures and affect the mobility of P in manure-amended soils. We studied the speciation of P in manures produced by broiler chickens and turkeys from either normal diets, or diets with reduced amounts of non-phytate phosphorus (NPP) and/or phytase, using a combination of chemical fractionation and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. All broiler litters were rich in dicalcium phosphate (65–76%), followed by aqueous phosphate (13–18%), and phytic acid (7–20%); however, no hydroxylapatite was observed. Similarly, normal turkey manure had 77% of P as dicalcium phosphate and had no hydroxylapatite, while turkey manure from diets that had reduced NPP and phytase contained equal proportions of dicalcium phosphate (33–45%) and hydroxylapatite (35–39%). This is attributed to the higher total Ca to P ratio (>2) in modified turkey manures that resulted in transformation of more soluble (dicalcium phosphate) to less soluble P compounds (hydroxylapatite). Chemical fractionation showed that H2O-extractable P was the predominant form in broiler litter (56–77%), whereas aqueous phosphate determined with XANES was <18% indicating that H2O probably dissolved mineral forms of P (e.g., dicalcium phosphate). Results show that HCl extraction primarily removed phytic acid from broiler litters and normal turkey manure, while it removed a mixture of hydroxylapatite and phytic acid from modified turkey manures. The combination of chemical fractionation and XANES provided information about the nature of P in these manures, which may help to devise best management practices for manure use.

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