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This article in AJ

  1. Vol. 96 No. 3, p. 761-768
    Received: June 30, 2003

    * Corresponding author(s): nchien@ifdc.org
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Greenhouse Evaluation of Phosphorus Sources Produced from a Low-Reactive Brazilian Phosphate Rock

  1. L. I. Prochnowa,
  2. S. H. Chien *b,
  3. G. Carmonab and
  4. J. Henaob
  1. a Dep. of Soil and Plant Nutrition, Univ. of São Paulo/ESALQ, C.P. 9, 13418-900, Piracicaba, Brazil, and IFDC, P.O. Box 2040, Muscle Shoals, AL 35662 during 1999–2001
    b IFDC, P.O. Box 2040, Muscle Shoals, AL 35662


The Patos de Minas phosphate rock (PR) in Brazil is not suitable for direct application due to its low reactivity or for commercial production of P fertilizers because of its high Fe-Al content. The objective of this study was to investigate the potential agronomic effectiveness of P sources with low water solubility produced from the PR. The P treatments were (i) compacted granular Patos PR with a single superphosphate (SSP) containing high water-soluble P content at a P ratio of 50:50, (ii) powdered low-grade single superphosphate (LG SSP) produced from Patos PR with low water solubility, (iii) powdered Patos PR, (iv) powdered mixture of PR and SSP at 50:50 P ratio, and (v) compacted granular SSP. The P sources were incorporated into an acid soil with pH 5.3 at 0, 10, 25, 50, and 100 mg P kg−1 to grow wheat (Triticum aestivum L.) and ryegrass (Lolium perenne L.) as test crops in a greenhouse study. We confirmed that Patos PR was low in agronomic effectiveness, only 1 and 30% as effective as SSP in producing dry matter yield of wheat and ryegrass, respectively. There were no significant differences between LG SSP or compacted PR+SSP [PR+SSP(C)] and SSP in dry matter yields of both crops, whereas mixed PR+SSP was less effective than PR+SSP(C) compared with granular SSP. Compacted PR+SSP and LG SSP can be potential P sources to be produced from the low-grade PR that could not be used either for direct application or acidulated P fertilizers.

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