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This article in SSSAJ

  1. Vol. 50 No. 3, p. 770-776
    Received: Nov 16, 1984



Effect of Sulfate on Ionic Transport and Balance in a Slightly Acidic Forest Soil1

  1. P. K. Khanna,
  2. G. T. Weaver and
  3. F. Beese2



Sulfate (CaSO4) was percolated at low (1.4 mg S L−1) and high (60.8 mg S L−1) concentrations, in a solution of composition equivalent to that of the canopy drip under beech (Fagus sylvatica L.) forests, through undisturbed columns of a slightly acid soil (Terra Fusca Rendzina or Lithic Rendoll). Concentrations of Ca2+, Mg2+, NO-3, and probably HCO-3 increased and of K decreased in the percolates. Decomposition of soil organic matter caused a significant production and subsequent leaching loss of 1.0 mmolc m2 of NO-3 during the experimental period of 156 d. Sulfate was released by the soil during the phase of low SO2-4 addition but was retained during the phase of high SO2-4 addition. Production of NO-3 and probably HCO-3, retention and release of SO2-4, and the release of cations involved a significant amount of production/consumption of protons in the soil. Calcium (II) and Mg2+ were leached from the soil but K+ was retained. Breakthrough curves showed peaks, usually wide, for cations when about two pore volumes of solutions had been replaced. Sulfate behaved as a reactive ion in this soil and its transport could be described by a solute transport model using suitable parameters (adsorption isotherms, apparent diffusion coefficients, bulk density, and water content), which were obtained from independent studies.

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