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This article in SSSAJ

  1. Vol. 31 No. 2, p. 168-171
    Received: Dec 27, 1965
    Accepted: Nov 21, 1966

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Composition of Dilute-Acid-Fluoride (Bray P1) Extracts of Illinois Soils1

  1. H. L. S. Tandon,
  2. H. L. Motto and
  3. L. T. Kurtz2



The Bray P1 reagent (0.03N NH4F + 0.025N HCl) is widely used to extract “available P” from soils, but few studies have been made to determine the other elements that it removes with P. Illinois soils differing in pH and P fertilization were extracted with the P1 reagent and also separately with its two components, 0.025N HCl and 0.03N NH4F. These extracts were analyzed for P, Al, Fe, Ca, Mg, Mn, and Si. Phosphorus extracted by the P1 reagent or by 0.03N NH4F was not correlated with soil pH or any of the other elements extracted. Combinations of Al with P in the soil, if they existed, could have been masked since the Al extracted by P1 and by 0.03N NH4F were many times greater than the P extracted. Phosphorus removed by 0.025N HCl was positively correlated with soil pH and with the Ca and Mg in the same extracts. From most soils the P1 reagent removed more P than the sum removed separately by 0.03N NH4F and 0.025N HCl. However, the reverse was true for a soil naturally high in calcium. Removal of the “Al-P” fraction of Chang and Jackson markedly reduced the P removed in a subsequent extraction with the P1 reagent. Also, very little Al was extracted by P1 after the “Al-P” fraction had been removed.

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