HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Syers, J. K. Articles by Williams, J. D. H. Search for Related Content PubMed Articles by Syers, J. K. Articles by Williams, J. D. H. Agricola Articles by Syers, J. K. Articles by Williams, J. D. H.

Calcium Fluoride Formation During Extraction of Calcareous Soils with Fluoride: I. Implications to Inorganic P Fractionation Schemes¹

ABSTRACT

Added inorganic P sorbed during 0.5M NH₄F extraction of calcite or aragonite was recovered in subsequent citrate-dithionite-bicarbonate (CDB) and HCl extractions of the Williams et al. (1967) inorganic P fractionation scheme. The sorbed P was shown to be associated with CaF₂ formed by the replacement of CaCO₃ during the NH₄F extraction. Similar results were obtained for soils which contained calcite but no P fertilizer reaction products. Thus, the amounts of non-occluded Al- and Fe-bound P (NH₄F- and NaOH-extractable) were underestimated whereas reductant-soluble P (CDB-extractable) was overestimated and acid-extractable Ca-P frequently overestimated. In contrast, magnesite, dolomite, and a dolomitic soil sorbed only a low proportion of added P during NH₄F extraction. A modified fractionation procedure, developed for calcareous soils, omitted the NH₄F extraction and involved sequential extraction with (i) NaOH to remove nonoccluded Fe- plus Al-bound P, (ii) NaCl and citratebicarbonate (CB) to remove P sorbed by carbonates during the preceding NaOH extraction, (iii) CDB to remove occluded P (reductant-soluble P), and (iv) HCl to remove Ca-bound P. Phosphorus added with the NaOH reagent to carbonate minerals and calcareous soils was recovered during the NaOH, NaCl, and CB extractions, enabling differentiation of nonoccluded Fe- plus Al-bound P from occluded P. The procedure also permitted a more meaningful separation of nonoccluded Fe- plus Al-bound P and Ca-bound P, particularly in calcareous soils which contained P fertilizer reaction products.

¹ Contribution from the Department of Soil Science, Univ. of Wisconsin, Madison, and the Canada Centre for Inland Waters, Burlington, Ontario. Research supported by the College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison, by the Kellogg Foundation, and by Hatch (Project 1693).

² Associate Professor of Soil Science, Univ. of Wisconsin, Madison; Research Fellow on leave from University College, Dublin, Ireland; and Research Scientist, Canada Centre for Inland Waters, Burlington, Ontario, Canada.

Received for publication January 7, 1971. Accepted for publication September 29, 1971.