Influence of parent material and time on properties of some hapludalfs from loess in West Tennessee

In the loess areas of West Tennessee, well-drained upland soils which formed under similar climate and organisms have been mapped extensively as members of the Memphis series. However, the morphology of all the soils is not always the same. For example, soils in thin loess have redder B horizons, more strongly developed blocky structure, higher sand content, and more prominent clay films than do soils in thick loess near the bluff. With such differences in morphology, it is logical to assume that chemical, physical, and mineralogical properties differ also. Therefore, the main objective of this study was to determine physical and chemical properties of these Hapludalfs at various distances from the bluff and relate any differences to one or more of the soil forming factors. A second objective was to classify these soils according to the seventh approximation. Two transects, parallel and 20 miles apart, were extended from the bluff southeastward for 50 miles across thick, intermediate, and thin loess areas. On high gently sloping positions along each transect, pedons were selected in each of the three loess areas. Each pedon was described and sampled to a depth of at least 150 cm. Exchangeable bases, pH, exchangeable acidity, CEC, and free iron oxides were determined in the laboratory, along with particle size distribution, bulk density, and moisture retention. Soils in thin loess had lower base saturation, lower CEC, less extractable P, lower Ca/Mg ratios, and a higher sand content than the soils in thick loess. Soils in thin loess are polygenic and. formed from Wisconsin and Loveland loess. Soils in thick and intermediate loess have formed in Peorian. Soils in Peorian loess were classified as Typic Hapludalfs belonging to the Memphis series. Soils in thin loess are definitely out of the Memphis series because the content of sand coarser than very fine exceeds 5 percent at 62 cm in soil 5 and at 55 cm in soil 6. Soil 6 was classified as an Ultic Hapludalf belonging to the Lexington series. Although similar to soil 6 in most properties, soil 5 was barely too high in base saturation for an Ultic Hapludalf.