Relating Sulfate Adsorption to Soil Properties in Michigan Forest Soils
1990
MacDonald, Neil W. | Hart, James B.
Six Michigan forest soil series comprising several gradients in soil physical and chemical properties were studied to relate SO₄ adsorption to soil properties. The series studied were Grayling (mixed, frigid Typic Udipsamments), Rubicon (sandy, mixed, frigid Entic Haplorthods), Kalkaska (sandy, mixed, frigid Typic Haplorthods), Montcalm (coarse-loamy, mixed Eutric Glossoboralfs), Spinks (sandy, mixed, mesic Psammentic Hapludalfs), and Oshtemo (coarse-loamy, mixed, mesic Typic Hapludalfs). Six randomly located map units of each series were sampled in the lower peninsula of Michigan. An index of SO₄ adsorption potential was determined by shaking samples in solutions containing 0.312 mmol SO₄-S L⁻¹ and measuring the loss of SO₄ from solution. The highest SO₄-adsorption potentials were found in Bw, Bs, and Bhs horizons of the Grayling, Rubicon, Kalkaska, and Montcalm series (7.0 to 14.1 mg S kg⁻¹) and in E and Bt horizons of the Spinks and Oshtemo series (4.3 to 10.1 mg S kg⁻¹). Significant differences in adsorption among series were present when comparing the upper 50 cm or the 100- to 150-cm depths in subsurface horizons, related to differences in Al, Fe, and clay concentrations. Sulfate adsorption was positively correlated with dithionite-citrate and ammonium oxalate extractable Al concentrations in subsurface horizons of the soils studied (r = 0.69–0.90). Regression analyses indicated that SO₄ adsorption could be predicted using variables derived from commonly measured soil properties (Al, Fe, pH, organic C, extractable P), with maximum R² values ranging from 0.83 to 0.89.
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