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This article in JEQ

  1. Vol. 29 No. 6, p. 1931-1938
    Received: Jan 4, 2000

    * Corresponding author(s): j.s.robinson@reading.ac.uk


Phosphorus Reactions and Leaching Potential in Soils Amended with Sewage Sludge

  1. Muhammad Tariq Siddique,
  2. J. Stephen Robinson * and
  3. Brian J. Alloway
  1. Department of Soil Science, The Univ. of Reading, Whiteknights, P.O. Box 233, Reading RG6 6DW, UK.



The objective of this study was to evaluate the leaching potential of P from a range of sewage sludge- or P fertilizer (monocalcium phosphate)-amended topsoils that had different P contents. Leaching trials (70 d) were conducted in 30-cm-long PVC columns; P-related parameters were then determined at different depths in the leached soils. In most cases, more (P < 0.01) P was released from the P-fertilized than sludge-treated soils. Increasing native Olsen P from 15 to 62 mg kg−1 had negligible effect on P release; however, there was a sharp increase in P leached between 92 and 134 (maximum) mg Olsen P kg−1. This increase was much greater in the P-fertilized than sludge-treated soils. At all depths in all leached soils, resin P decreased in the order: P fertilized > sludge > control. At the lowest depth (16–20 cm) of the leached soil, the degree of P sorption saturation decreased in the same order and was related curvilinearly (P < 0.001) to cumulative P leached (at 70 d). This relationship demonstrates the importance of P sorption saturation in controlling P leaching in sludge- and fertilizer-treated soils. The more rapid rate of P saturation and P leaching in P-fertilized than sludge-treated soils emphasizes the role of the P source in adsorption-desorption processes.

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