Soils with Spodic Characteristics on the Eastern Shore of Maryland

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A seasonally fluctuating water table may be an important factor in the formation of spodic horizons in sandy, quartzose sediments on the Lower Eastern Shore of Maryland. This study was conducted to examine spodic horizon formation and expression along two topohydrosequences. After a reconnaissance study, two research sites were chosen in the Pocomoke State Forest in Worcester County, Maryland. The soils were classified according to Soil Taxonomy as siliceous, mesic, Typic Quartzipsamments, Aquic Haplorthods, and Aerie and Typic Haplaquods. The spodic horizons were thickest (26-204cm) in the wettest positions. Total organic carbon, pyrophosphateextractable carbon, and extractable aluminum were greatest in the spodic horizons, and there was little extractable iron in the Haplaquods. There was less structural aluminum and potassium in the surface horizons than in the lower horizons. This suggests that feldspar weathering in the surface horizons provides a source of aluminum for the spodic horizon formation. Quantitative estimates of pedogenesis showed net gains of extractable aluminum, total (organic) carbon, and pyrophosphate carbon in the lower landscape positions. The seasonally fluctuating water table appears to influence the movement of soluble organic aluminum complexes through the soil downslope, as well as within the pedon from the surface to subjacent horizons.