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This article in SSSAJ

  1. Vol. 22 No. 1, p. 29-32
    Received: May 24, 1957
    Accepted: July 11, 1957

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Calcium Phosphate Fertilizers: II. A Petrographic Study of Their Alteration in Soils1

  1. J. R. Lehr and
  2. W. E. Brown2



As a supplemental study to pot-culture tests in which six calcium phosphates were investigated, petrographic examinations were made of the fertilizer residues and surrounding soils. The materials tested were Ca(H2PO4)2 · H2O, CaHPO4 · 2H2O, CaHPO4, Ca4H(PO4)3 · 3H2O, Ca3(PO4)2, and Ca10(PO4)6(OH)2).

The purpose was to determine the physical and chemical alterations that the materials had undergone while in a soil environment and in the presence of feeding roots. Correlations between these observations and plant response were sought.

Some correlation was found between plant response and; (a) relative rates of solution or solubilities of the phosphates, and (b) chemical alterations of the phosphates. Positive evidence was found for 4 hydrolysis reactions, 2 of which confirm the postulated formation of octocalcium phosphate and apatite. Other observations lend new support to the concept of contact feeding by plant roots.

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