Variability of the Cecil Map Unit in Appomattox County, Virginia
- P. J. Thomas,
- J. C. Baker and
- T. W. Simpson
A study was initiated in Appomattox County in the southern Piedmont of Virginia to assess composition and variability of a Typic Kanhapludult map unit. Five delineations of the Cecil (clayey, kaolinitic, thermic Typic Kanhapludults) map unit, three to eight sites within each delineation, and three profiles within each site were randomly located in a two-level nested sampling scheme. Soil physical, chemical, and morphological data were collected from the Ap, Bt, and BC horizons of each profile. Fifty-eight percent of the 81 profiles met the criteria for the Cecil soil series. Seventy-one percent of the profiles were taxonomically similar to Cecil. The remaining 29% were taxonomically dissimilar inclusions. Thus, the map unit name would be Cecil and the map unit description would include dissimilar soils. Taxonomic variability was reflected in variability of taxonomically important soil properties. Percent base saturation decreased with depth in the profile. Maximum clay distribution occurred in the Bt horizon and ranged from 25 to 75%. The solum exhibited large variation in thickness. Subsoil properties important to mapping (percent base saturation in the chemical control section, clay percentage in the particle-size control section, and solum thickness) exhibited considerable variation within delineations but the variability was consistent from delineation to delineation. Intrusions of mafic material into the felsic crystalline system, from which Cecil and similar soils form, accounted for most of the variability in the soil properties.
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