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Regional geochemical reconnaissance and compositional variations in grain and forage crops on the Southern Canadian Interior Plain

University of British Columbia

The distribution of Cu, Fe, Mn, Zn, Mo and Se in earth surface materials on the Southern Canadian Interior Plain was examined with the aim of recommending appropriate methods of producing regional geochemical maps. Investigations were undertaken in three separate areas, one in each of the prairie provinces, selected to represent a range of environmental conditions. In the Swan River - Dauphin area emphasis was placed on investigating the regional distribution of Mo in both soil and stream sediment. These patterns were related to data on the Mo status of plants and to information on Mo-induced Cu deficiency in cattle. In the Rosetown area of Saskatchewan, and the Red Deer area of Alberta, attention v/as focussed on examining variations in the Cu, Fe, Mn, Zn and Se content of soils; in the Rosetown area concentrations of these elements in whole wheat plants were also determined. Procedures for regional geochemical mapping using stream sediment are well established. On the Southern Canadian Interior Plain, however, stream density is generally inadequate for routine application of these techniques. Although tributary drainages are relatively common in parts of southern Manitoba, results of investigations in the Swan River - Dauphin area indicate that Mo concentrations in stream sediment typically reflect Mo levels in upstream soil, but not those of associated plants. In contrast to findings reported by V7ebb and his associates in the United Kingdom, Manitoba stream sediment data are of little value in identifying areas where potentially toxic Mo concentrations are likely to occur in forage. Reconnaissance surveys based on soil sampling, on the other hand, can be applied throughout the Canadian prairies. Results of studies around Rosetown and Red Deer indicate that regional compositional trends for soil may be efficiently described in terms of variations among means estimated for individual soil parent materials. In the Rosetown area, for example, over 70% of the total variance for Cu, Fe, Mn and Zn in A horizons is attributable to differences among parent material means. This parent material effect appears, in turn, to be mainly a function of textural variations, with lowest concentrations associated with sand-rich and highest with clay-rich deposits. The importance of differences among means for soil associated with individual surficial deposits is also emphasized, in the Rosetown area, by relatively strong positive relationships (r>0.73) between parent material based Mn, Fe and Cu means for wheat and soil. When data are considered on an individual sample basis relationships between plant and soil concentrations are generally much weaker (r< 0.40). It is suggested, therefore, that on the Southern Canadian Interior Plain, regional geochemical maps can be efficiently produced using parent material based soil compositional data. The procedure recommended involves collection of A horizon samples at randomly chosen sites over each of the major parent materials recognized, and estimation of geometric mean and deviation values for each deposit. Duncan's New Multiple Range test is used to identify significant differences among means, and results are summarized in map form, showing only composition-ally distinctive parent materials or parent material groups. In view of close relationships noted between parent material based means for soils and plants, maps produced in this fashion should be useful in identifying areas where trace element excesses or deficiencies are limiting crop or livestock productivity.

Text

2010-02-19

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http://hdl.handle.net/2429/20579

Geological Sciences

University of British Columbia

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