Multiple bands or strata of soil materials, which are finer textured and browner or redder colored than the material above or below, have been studied. These bands are common in unconsolidated sandy Coastal Plain and glacial deposits. In Virginia, North Carolina, and South Carolina they are found to lie nearly horizontally, are much deeper where the present soil is nearly level than on sloping soil areas, and the soils in which they occur contain “clay balls” and band segments above the continuous bands. Stratification within the bands, charcoal fragments deposited with the sand, and bands showing scour and fill characteristics were observed in the field. In no instance were yellowish‐red bands found to cross bedding planes but rather the redder color follows the texture of the strata.
Chemical analyses show that these bands, where continuous, contain more organic matter, and have a slightly lower pH and higher cation‐exchange capacity than the interbands. Percentage free iron in the clay fraction, and clay mineral analyses show no significant differences between the bands and interbands.
Attempts to develop clay‐iron oxide strata in the laboratory by leaching unstratified soil materials were unsuccessful. However, some were developed in stratified materials when leached with a complexing or reducing agent. These experiments produced evidence that clay movement in a sandy medium is similar under some conditions to clay movement in a finer textured medium and give support to the conclusion that the bands studied are primarily the result of geologic deposition.
Based upon this conclusion, it is proposed that the part of the profile containing such bands be considered as the C horizon of the soil above. The small residual “clay balls” or segments of bands remaining in the B horizon (often a color B) would be considered as fragments of parent material and comparable to partially weathered rock fragments in the lower B of a residual soil.
Within Sudan there are extensive areas of Vertisols in the Nile River valley south of Khartoum. These soils have clay contents ranging from 40 to 60 per cent, very slow permeability, exchangeable sodium percentages up to 35 or more in the upper 60 a, and pH values between 8.0 and 9.6. Under present management, satisfactory yields of long staple cotton are obtained under irrigation on soils having exchangeable sodium percentage (ESP) of up to 35 in the upper 60 cm. It is proposed that soil characteristics such as type of clay, cracking and exchangeable sodium in the hot, dry climate of Sudan influence soil structure and water availability and thus the yields of cotton.
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