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This article in SSSAJ

  1. Vol. 33 No. 3, p. 460-463
    Received: Sept 25, 1968



Phosphorus Availability to Corn as Affected by Granulating Manganese with Ortho- and Pyrophosphate Fertilizers1

  1. P. M. Giordano and
  2. J. J. Mortvedt2



The presence of MnSO4 at a level of 10% Mn in granular ammonium polyphosphate (APP) and triammonium pyrophosphate (TPP) significantly reduced corn (Zea mays L.) forage yields and P uptake relative to treatments where P and Mn were applied separately in greenhouse pots. A significant reduction in P uptake resulted when MnSO4 was combined with monoammonium phosphate (MAP), but no yield reduction occurred.

Chemical extraction of the fertilizers indicated that the solubilities of both P and Mn were reduced when MnSO4 was granulated with APP or TPP. A compound of very low solubility, Mn(NH4)2P2O7 · 2H2O, was identified as the principal reaction product. Accordingly, movement of P in soil was restricted to a greater extent when MnSO4 was combined with TPP than with MAP.

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