Characterization and composition of selected Cecil map units in the Virginia Piedmont

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Virginia Agricultural Experiment Station

A study in Appomattox, Pittsylvania, and Lunenburg counties in the southern Piedmont of Virginia assessed composition and variability of a map unit named for a taxon of Typic Kanhapludults. Twelve delineations of Cecil sandy loam, 2 to 7 percent slopes, 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 C horizons of each profile. In Appomattox County, 38 percent of the 81 profiles met the criteria for the Cecil soil series. An additional 33 percent of the profiles were taxonomically similar to Cecil. The remaining 29 percent were taxonomically dissimilar inclusions. In Pittsylvania County, 48 percent of the 75 profiles were Cecil series. An additional 47 percent of the profiles were taxonomically similar to Cecil. The remaining 5 percent were taxonomically dissimilar inclusions. In Lunenburg County, 42 percent of the 45 profiles were the Cecil series; the remaining 58 percent of the profiles were taxonomically similar to Cecil. Thus, the map unit in all three counties would be named Cecil and the map unit description in Appomattox and Pittsylvania counties would include dissimilar soils according to National Cooperative Soil Survey criteria. Taxonomic variability was reflected in the variability of taxonomically important soil properties. Percent base saturation decreased with depth in the profile. Maximum clay content occurred in the Bt horizon and ranged from 25 to 75 percent. The solum exhibited large variation in thickness. Subsoil properties important to classification (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, probably accounts for most of the variability in soil properties. Low plant available water, low bases, and high P-fixing capacity are major management concerns of the Cecil and similar soils. Understanding the interrelationship between map unit composition, variability, and soil properties is essential in increasing the productivity of these major landscape units.