Genesis, Mineralogy, and Micromorphology of Vertic Soils in Southeastern Kansas.

Many of the soils in the Cherokee Prairies region of southeastern Kansas are characterized by high clay contents and high shrink-swell potentials.  These vertic properties and claypan characteristics cause soil management to be difficult and pose problems for agricultural, environmental, and engineering uses.  The objective of this study was to determine why some claypan soils have developed the cracking characteristics of a vertic soil while other soils in the region with high clay contents lack the vertic properties.  Differences in clay mineralogy were hypothesized to be a primary reason for the variation in the expression of vertic properties.  A secondary objective was then to examine why these differences in clay mineralogy exist.  Clay mineralogy also affects other processes such as K⁺ and NH₄⁺ fixation.  Thus, a third objective was to evaluate the potential for K⁺ and NH₄⁺ fixation based on clay mineralogy data.  Five pedons were sampled and described throughout the region.  Laboratory analyses included pH, total C, cation exchange capacity, particle size distribution, and clay mineralogy.  Thin sections were analyzed for selected horizons with a petrographic microscope.  Soils in the field exhibited a range of cracking characteristics.  Four of the pedons exhibited slickensides.  Three of the pedons showed a dominance of smectite in the clay fraction while two had a more mixed mineralogy.  Vermiculite was present in most surface horizon samples; thus, the potential for K⁺ and NH₄⁺ fixation is present.  In conclusion, the data suggested that differences in clay mineralogy do exist among the soils studied; however, the expression of vertic properties is dependent upon many other possible factors such as landscape position and microclimate.