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The behaviour of iron and trace elements down catenary sequences in West Central Saskatchewan

University of British Columbia

Doyle (1977, 1979), working on the Southern Canadian Interior Plain evaluated regional geochemical patterns based on parent material. He found that regional variation in the total concentration of copper, iron, manganese and zinc arose largely from differences among parent materials, rather than from more local (within parent material) differences caused by pedological factors. To extend Doyle's work, a more detailed local investigation of the within parent material variation of copper, iron, manganese and zinc on four parent materials was carried out in the Rosetown area, Saskatchewan. Principal objectives of this study were to find the causes and magnitude of downslope catenary changes in the geochemical pattern on each of four soil parent materials, utilizing DTPA extraction to indicate the availability of these micronutrients to crops. Soil samples were collected from soils developed on lacustrine clay (Regina Soil Series), lacustrine silt (Elstow Soil Series), glacial till (Weyburn Soil Series) and aeolian sand (Dune Sand Soil Series). Five sites were selected for each parent material and at each site, five pits were dug at intervals downslope. Laboratory analysis for the entire sample set included the determination of pH, organic matter, copper, iron, manganese and zinc concentrations for soil digested with 4:1 HNO₃/HClO₄ mixture and the same metals extracted with DTPA solution. Further analysis comprised sequential extraction of copper, iron, manganese and zinc, particle size separation and X-ray diffraction. Highest total elemental concentrations are found in the Ap horizon of the Rego Dark Brown Chernozems developed on lacustrine clay, followed by lacustrine silt and glacial till soils, with soils on aeolian sands having the lowest values. The A horizons of lacustrine silt soils contain the highest DTPA extractable concentrations of iron, manganese and zinc, whereas, maximum extractable concentrations in the C horizons are associated with lacustrine clays. DTPA extractable copper in both A and C horizons is at a maximum in lacustrine clay soils. For the majority of sites, the highest total and DTPA elemental concentrations occur at the base of the slope, this being most marked for lacustrine silt soils. Total elemental concentrations for the four parent materials exhibit a relatively greater uniformity when considering both trends downslope and down profile than DTPA concentrations. A much greater proportion of DTPA extractable manganese and zinc occurs in the organic rich surface horizons compared to the more alkaline C horizons. This is also found for copper and iron but to a lesser extent. Analysis of variance shows that the compositional variation among parent materials for total elemental data, accounts for well over 50% of the overall data variability. Duncan's New Multiple Range test results further substantiate these textural groupings into lacustrine clay, lacustrine silt and glacial till and aeolian sand. Results are less conclusive for DTPA elemental data. However, even though soil copper, iron, manganese and zinc are influenced by many pediological factors operating separately and jointly, a large percentage of the total variability when predicting DTPA elemental concentrations can be accounted for by the variables included in the regression equations. The Index of Determination (I ) shows that the variability in DTPA elemental concentrations is best accounted for by the regression equations for the lacustrine clay soils with 93-98% of the total variability explained.

Text

2010-03-30

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http://hdl.handle.net/2429/23129

Soil Science

University of British Columbia

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