The genesis and morphology of three southwest Virginia soils which were developed from material weathered from limestone

Abstract

The genetic and morphological characteristics of Hagerstown silt loam, Pisgah silt loam and Clarksville cherty silt loam, three southwest Virginia soils which were formed from material weathered from limestone, were studied by means of mechanical and chemical analyses, and field studies or the soil profiles.

The soils used in this investigation are all related in a general way, that is, they all occur within the Gray-Brown Podzolic region and are all derivatives of relatively highly carbonated rocks.

Samples of all three soils were taken in Russell County, Virginia within the same vicinity. Therefore, the variation in the physical and chemical composition are due to variation in parent rock and relief and not to variations in climate.

Chemical analyses of the parent rock showed that the Hagerstown silt loam and Clarksville cherty silt loan were formed from material weathered from a dolomitic limestone, and that the Pisgah silt loan was formed from material weathered from a high grade limestone.

Total chemical analyses of the various horizons of the soil profiles showed that the soil forming processes of the three soils studied were podzolic is nature.

The parent materials or C horizons of all the soil profiles studied were clays. Hagerstown, which contained approximately 38 percent clay in the A₁ horizon and 75 percent clay in the C horizon, was the heaviest of the three soils studied.

Laboratory and field classifications of soil class conflicted in the case of the Hagerstown profile.

The ratios of silica to alumina, and silica to iron showed clearly the accumulation of alumina or iron in the lower horizons. The base to alumina ratio showed the thoroughness of the weathering of the three soil profiles.

Calculations of the percentages of bases lost during the soil forming processes showed that calcium was lost from the soil to a greater extent than the magnesium.