Pedogenic influences on soil cadmium, and phytoavailability in selected agricultural soils from the prairie ecozone

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Malegus, Ross C.
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Recent grain Cd analyses have identified the Brown soil zone and the Morden, Manitoba region in the prairie ecozone as producing higher Durum wheat grain Cd than other parts of the prairies. An investigation of some prairie ecozone soils was undertaken. Two soil forming factors: parent material and climate were studied from a general survey of the prairie ecozone. Soil samples were collected from a climosequence of 13 pedons on a genetic basis from the Brown, Dark Brown, Black, and Dark Gray Soil zones. A lithosequence representing different parent materials was also used to select sites for this general survey. The Ap horizon contained the largest amount of total soil Cd. Cadmium enrichment factors (A horizon/C horizon) for the Brown, Dark Brown, Black, Dark Gray, and Gray Luvisol Great Groups were 1.38, 1.73, 2.04, 0.787, and 0.833, respectively. Cadmium content in parent material followed the order: shale till $>$ lacustrine $>$ mixed till parent material. Different rock sources for parent material accounted for the Cd lithosequence. A more detailed survey was initiated from a specified area of lacustrine parent material known for producing grain with high Cd. This survey occurred over an 80-kilometre transect of the Red River Valley of southern Manitoba. The transect included eleven agricultural fields. Mean surface soil total Cd content was 0.876 mg Cd kg$\sp{-1}.$ Mean grain Cd content was 0.094 ppm (f.w.). Soil Cd was greater in the surface soil compared to sub-surface soil. Soil Cd and grain Cd increased with increasing clay content. A statistically significant positive correlation was observed between surface soil total Cd and grain Cd. A statistically significant negative correlation was observed between the sub-surface ratio of total soil Zn/Cd and grain Cd. (Abstract shortened by UMI.)