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This article in SSSAJ

  1. Vol. 23 No. 1, p. 3-7
    Received: May 15, 1958



Chemical Behavior of Monocalcium Phosphate Monohydrate in Soils1

  1. James R. Lehr,
  2. Walter E. Brown and
  3. Earl H. Brown2



To gain an insight into the phenomena that are initiated when superphosphate is placed in soil, tablets containing monocalcium phosphate monohydrate were placed in several soils and observed directly. Petrographic examinations and supporting chemical studies gave information on chemical reactions associated with the dissolution process and on the transport of materials to and from the tablet—factors that bear upon the distribution and chemical combination of the phosphorus and thus upon agronomic response.

The results suggest that capillary flow was a principal mechanism in the movement of phosphate solution away from the tablet. Vapor-phase transport of water to the tablet apparently controlled the rate of dissolution. A significant part of the P remained at the tablet site as dicalcium phosphate, anhydrous or dihydrated. The dissolution process was affected by soil type, soil moisture content, humus content, microbiological activity, capillarity of soil and tablet, time, and temperature.

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