Plinthite: Btv horizon (plinthic horizon)

Large fragments of the subsoil (Btx horizon) from a Fuquay soil that contains plinthite. Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor mixture of clay with quartz and other highly weathered minerals. It commonly occurs as reddish redox concentrations in a layer that has a polygonal (irregular), platy (lenticular), or reticulate (blocky) pattern and is commonly less than strongly cemented.

 

Plinthite irreversibly hardens upon exposure to repeated wetting and drying, especially if exposed to heat from the sun. Other morphologically similar iron-rich materials that do not progressively harden upon repeated wetting and drying are not considered plinthite. The horizon in which plinthite occurs commonly has 2.5 percent (by mass) or more citrate dithionite extractable iron in the fine-earth fraction and a ratio between acid oxalate extractable Fe and citrate-dithionite extractable Fe of less than 0.10.

 

For more information about a plinthic horizon, visit;

www.researchgate.net/publication/242649722_Rationale_for_...

or;

www.sciencedirect.com/science/article/pii/S00167061220043...

 

The Fuquay series consists of very deep, well drained soils that formed in sandy and loamy marine sediments of the upper Coastal Plain. Permeability is moderate in the upper part of the subsoil and slow in the lower part. Slopes range from 0 to 10 percent.

 

Taxonomic class: Loamy, kaolinitic, thermic Arenic Plinthic Kandiudults

 

Kandiudults are the Udults that are very deep and have a kandic horizon and a clay distribution in which the percentage of clay does not decrease from its maximum amount by as much as 20 percent within a depth of 150 cm from the mineral soil surface, or the layer in which the clay percentage decreases has at least 5 percent of the volume consisting of skeletans on faces of peds and there is at least a 3 percent (absolute) increase in clay content below this layer. These soils do not have a fragipan or a horizon in which plinthite either forms a continuous phase or constitutes one-half or more of the volume within 150 cm of the mineral soil surface. Kandiudults are of moderate extent in the Southeastern United States.

 

Arenic Plinthic Kandiudults soils have a layer, starting at the mineral soil surface, that has a sandy or sandy-skeletal particle-size class and is between 50 and 100 cm thick. They also have 5 to 50 percent (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. These soils are of small extent in the United States.

 

USE AND VEGETATION:

Major Uses: Cropland

Dominant Vegetation: Where cultivated--tobacco, cotton, corn, soybeans, and small grains. Where wooded--loblolly pine, longleaf pine, and slash pine, with some hardwoods, understory plants including American holly, flowering dogwood, persimmon, and greenbrier.

 

DISTRIBUTION AND EXTENT:

Distribution: Upper Coastal Plain of North Carolina, Alabama, Florida, Georgia, and South Carolina

Extent: Large

 

SERIES ESTABLISHED: Johnston County, North Carolina; 1965. The Fuquay series is a Benchmark soil. A benchmark soil is one of large extent within one or more major land resource areas (MLRAs), one that holds a key position in the soil classification system, one for which there is a large amount of data, one that has special importance to one or more significant land uses, or one that is of significant ecological importance.

 

For a detailed description, visit:

soilseries.sc.egov.usda.gov/OSD_Docs/F/FUQUAY.html

 

For acreage and geographic distribution, visit:

casoilresource.lawr.ucdavis.edu/see/#fuquay

 

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