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This article in SSSAJ

  1. Vol. 54 No. 5, p. 1345-1350
     
    Received: Feb 10, 1989


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doi:10.2136/sssaj1990.03615995005400050024x

Clover Residue Effectiveness in Reducing Orthophosphate Sorption on Ferric Hydroxide Coated Soil

  1. G. W. Easterwood  and
  2. J. B. Sartain
  1. Dep. of Soil Science, Univ. of Florida, Gainesville, FL 32611

Abstract

Abstract

In many tropical soil systems, secondary minerals are coated with sesquioxides, resulting in inherently low P availability to plants due to P-fixation mechanisms. Research was conducted to determine the influence of hydroponically grown clover (Trifolium repens L.) residue pretreatment in reducing orthophosphate sorption on a fine-loamy, siliceous, thermic Typic Paleudult (Orangeburg series) that had been coated with synthetically prepared amorphous Fe(OH)3. A 3 × 2 × 3 factorial experiment was conducted in split-split-plot design with P as the main plot, Fe(OH)3 as the subplot, and clover as the sub-subplot. Throughout two cropping periods of 50 d each, to assess the initial and residual effect of clover pretreatment, corn (Zea mays L.) dry-matter yield, P uptake, and Bray 2 extractable P levels were superior with clover pretreatment prior to P fertilizer addition. When fertilizers, but not clover, were again applied to experimental units for a third cropping period, clover pretreatment did not influence plant dry-matter accumulation or P uptake. It did, however, substantially increase Bray 2 extractable P levels. Potentiometric titrations relating to surface charge were conducted on treatments with Fe(OH)3 that had been amended with P, clover, and P plus clover after the first cropping period. Results suggest that organic acids from clover decomposition bind to Fe(OH)3 surfaces and are able to complex Lewis acid cations to increase P availability.

Contributed by the Inst. of Food and Agricultural Sciences, Univ. of Florida. Journal no. 9743.

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