The bulk density of soil samples obtained with a hydraulic soil coring machine, for both core segments and clods, was compared to the bulk density of soil samples obtained with a Uhland sampler and natural clods taken from a soil pit. Subsurface, upper B, and lower B horizon samples were compared. Clods gave bulk density values that were significantly higher than cores in the upper solum, where small structural units occur; however, in the lower solum, where soil structural units are large or massive, variation between clods and cores was not statistically significant. There was no significant difference in bulk density due to the method of obtaining clods or cores.
For Typic Argiudolls in Illinois the amount of pedogenic clay particles formed, over that inherited from the calcareous Peoria loess, seems to be controlled by rainfall frequency. The amount of solution leaching through the soil, as inferred from the amount of rainfall, was not related to the amount of pedogenic clay particles formed. This finding may help explain why the clay minerals found in the argillic horizon of some soils are not in the clay mineral stability field predicted by dilute solution chemistry.The distribution of clay within the soil profile is related to the amount and distribution of rainfall (leachable water), depth of leaching, and natural drainage class.
The Riker soil is a proposed soil series that forms on artificial landforms in thick coal ash deposits. Little is known about the physical, chemical, or mineralogical properties of such soil materials, even though they are frequent components of filled landforms in urban areas. Soils that form from these materials are unique and do not fit into the conventional classes of Soil Taxonomy, nor do they lend themselves to conventional lab analysis without careful interpretation. Full characterization analyses were performed on a pedon from New York City collected on a 30‐yr‐old coal ash pile. The soil had a unique bulk density, particle density, and particle size, and physically resembled a cindery volcanic soil. Particle size analysis indicated almost zero total clay, yet the 15 bar H2O water content and the CEC measured directly by NH4 replacement at pH 7 (CEC7) imply moderate clay content. X‐ray diffraction analysis showed that the clay fraction was made up of noncrystalline materials. High surface area and reactivity of the noncrystalline materials may explain the higher than expected 15 bar H2O water content and CEC7 values, along with contribution from soil organic compounds. Unburned coal and shale fragments, and burned ferric‐aluminosilicate aggregates also may contribute to the 15 bar H2O water content and CEC7. Some water also may be tightly held very deeply inside internal pores in the cinders. Though the soil physically resembles materials that may form Andisols or Spodosols, the soil does not have these properties. Further analyses are needed to fully understand the mineralogical properties of this soil material and soil series. Current lab methodologies do not easily or fully explain the unique properties of coal ash materials in urban soils. New classes need to be added to Soil Taxonomy to identify the characteristics of these soils separately from Udorthents formed in geologic deposits and pedogenic materials.
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