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Soil Science Society of America Journal Abstract -

Use of Isotopic Dilution in a Study of Inorganic Phosphorus Fractions from Different Soils1


This article in SSSAJ

  1. Vol. 29 No. 3, p. 259-262
    Received: Oct 5, 1964
    Accepted: Dec 28, 1964

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  1. Andrew D. Dunbar and
  2. Dale E. Baker2



The study consisted of a factorial experiment in which each of seven widely different soils was treated with 0 and 1 lime requirements and 0, 500, and 1,000 ppm of P. Prior to fractionating the soil P, a constant amount of P32 was added to each sample. The results indicate that for these acid soils, P was extracted predominantly with the aluminum phosphate and iron phosphate fractions. Results for isotopic dilution indicated that the different P fractions ranked in the following order with respect to amounts of active solid phase P removed per unit of solid phase P: water soluble P > aluminum phosphate > iron phosphate > calcium phosphate. The rapidity with which P32 reached an equilibrium with P extracted from soils with NH4F (aluminum phosphate) indicates why fluoride-extractable P has correlated highly with availability of soil P.

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