Abstract

Very few mineralogical data have been published for soils in Kentucky. As an initial attempt to classify mineralogy of the subsoil, a general mineralogy map of the state was constructed based on currently available information (Fig. 1). The map suggests that quartz, mica, and feldspars are the dominant minerals of the sqnd and silt size fractions and that illite, smectite, kaolinite and hydroxyinterlayered vermiculite or smectite dominate the clay size soil fraction. Soils of the Western Coalfields, Eastern Coalfields, and Eastern Pennyrile regions generally contain more quartz in the sand and silt fraction than soils of the Purchase, Western Pennyrile, and Bluegrass regions. The sand and silt fractions of the latter regions, although still dominated by quartz, contain significant amounts of potassium feldspars and mica. The feldspar component is generally more prominent in soils of Western Kentucky, with mica being more prominent in central and eastern parts of the state. Soils with high feldspar or mica content are considered to have adequate water-soluble, exchangeable, and non-exchangeable IC-supplying capacity because of the potassium released from their mineral structure during weathering. However, muscovite-type micas are more resistant to weathering than feldspars, with a rate of IC-release not fast enough to replenish the solution K as it is removed by plants. Furthermore, not all mica-type minerals contain the same amount of Kin their crystal structure (muscovite 11%, glauconite 5%, biotite 8%). Potassium availability to plants in these soils also depends on the rate and duration of ion exchange reactions, the nature of which is affected by soil mineralogical composition, IC-specificity for certain exchange mineral sites and the nature of other ions in solution.

Publication Date

1-1985

Volume

6

Number

1

Included in

Soil Science Commons

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