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This article in SSSAJ

  1. Vol. 56 No. 1, p. 89-95
    Received: Feb 27, 1991

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Solution Sulfate Chemistry in Three Sulfur-Retentive Hydrandepts

  1. J. D. Wolt *,
  2. N. V. Hue and
  3. R. L. Fox
  1. DowElanco North American Environmental Chemistry Lab., Midland, MI 48641
    Dep. of Agronomy and Soil Science, College of Tropical Agriculture and Human Resources, Univ. of Hawaii, Honolulu, HI 96822. Contribution from the Dep. of Agronomy and Soil Science, Univ. of Hawaii and DowElanco.



Highly S-retentive Hydrandepts frequently contain large quantities (> 200 mmol kg-1) of sorbed S while exhibiting low S intensities in soil solution. Solution-solid phase S relations for three representative Hydrandepts from Hawaii were investigated in terms of the nature of sorption isotherms and the role of basic Al hydroxysulfate precipitation as a mechanism for S retention. Sorption data were fit to linear, Langmuir, and multisite Langmuir isotherms using a modeling routine that performed parameter estimates and model optimization using weighted nonlinear fitting. Best-fit models indicated sorption data were adequately described by Langmuir isotherms. Total P-extractable SO4-S increased markedly at depths > 45 cm and tended to decline at depths > 120 cm. Extractable SO4-S was strongly regressed on gravimetric moisture content, a relative indicator of reactive surface for these thixotropic soils. Soil solution SO4-S concentrations were consistent with alunite or basaluminite solubility when gibbsite controlled solution Al3+.

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