title: Preliminary validation of a sequential fractionation method to study phosphorus chemistry in a calcareous soil.
abstract: A sequential fractionation method proposed by Jiang and Gu (1989) distinguished three types of calcium phosphates (Ca-P) according to their different plant availabilities. Three extractants, NaHCO3, NH4Ac, and H2SO4 were used to extract Ca2-P, Ca8-P, and Ca10-P types, respectively, from soil. This sequential fractionation method was tested and modified for analyzing the P chemistry of a calcareous soil. The solubility test and the model diagrams of the stability of the major Ca-P minerals showed that NaHCO3 was able to extract brushite (Ca2-P type), and NH4Ac extracted brushite and β-tricalcium P (Ca8-P type) as well as hydroxyapatite (Ca10-P type). Therefore the P forms targeted by extraction with NH4Ac should include both Ca8-and Ca10-P types. The sum of the P extracted by all extractants in the sequential fractionation method in the calcareous soil was in agreement with the total P measured by the perchloric acid digestion method. A proportion of organic P measured by the sequential fractionation method was in agreement with the result from solution (31)P NMR spectroscopy. This study showed that the modified sequential fractionation method and its target P forms would be useful for quantifying and characterizing inorganic and organic P in a calcareous soil, even though it should be used in combination with other techniques, such as solution (31)P NMR spectroscopy.
authors.affiliation: School of Environmental Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada. Electronic address: yaudette@uoguelph.ca.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Audette
authors.affiliation: School of Environmental Sciences, University of Guelph, Ridgetown Campus, Ridgetown, Ontario N0P 2C0, Canada.
authors.forename: Ivan P
authors.initials: IP
authors.lastname: O'Halloran
authors.affiliation: School of Environmental Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Les J
authors.initials: LJ
authors.lastname: Evans
authors.affiliation: School of Environmental Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: R Paul
authors.initials: RP
authors.lastname: Voroney
mesh_terms: D000085:Acetates / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D005591:Chemical Fractionation / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008903:Minerals / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D015203:Reproducibility of Results; D017693:Sodium Bicarbonate / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry
chemical_list: D000085:Acetates; D002130:Calcium Phosphates; D008903:Minerals; D012987:Soil; D013464:Sulfuric Acids; D010758:Phosphorus; D017693:Sodium Bicarbonate; C033158:sulfuric acid; C018824:ammonium acetate
keywords: Calcareous soil; Calcium phosphate; Phosphorus chemistry; Phosphorus fractions; Phosphorus minerals; Sequential fractionation method