Established Series


The Iuka series consists of very deep, moderately well drained, moderately permeable soils in the Southern Coastal Plain (MLRA 133A). They formed in stratified loamy and sandy alluvial sediments on nearly level flood plains. Near the type location, the average annual temperature is about 66 degrees F., and the average annual precipitation is about 54 inches. Slopes range from 0 to 2 percent.

TAXONOMIC CLASS: Coarse-loamy, siliceous, active, acid, thermic Aquic Udifluvents

TYPICAL PEDON: Iuka fine sandy loam, on a smooth, concave 0.5 percent slope, in a field (Colors are for moist soil).

Ap--0 to 7 inches; brown (10YR 4/3) fine sandy loam; weak medium granular structure; friable; common fine pebbles of chert and quartzite, moderately acid; abrupt smooth boundary. (0 to 8 inches thick)

A--7 to 13 inches; brown (10YR 5/3) fine sandy loam; single grain; friable; very strongly acid; gradual wavy boundary. (0 to 8 inches thick)

C--13 to 22 inches; light yellowish brown (10YR 6/4) fine sandy loam; few distinct thin strata of loamy sand; massive; friable; common medium distinct strong brown (7.5YR 5/6) masses of iron accumulation and common medium distinct grayish brown (10YR 5/2) areas of areas of iron depletions; very strongly acid; gradual wavy boundary. (8 to 40 inches thick)

Cg--22 to 60 inches; 50 percent gray (10YR 6/1) and 50 percent yellowish brown (10YR 5/4) sandy loam; common thin lenses of loamy fine sand and loam; massive; friable, few soft dark colored bodies in lower part; the areas of gray are iron depletions and the areas of yellowish brown are iron accumulations; very strongly acid.

TYPE LOCATION: Franklin County, Alabama. Approximately 2.1 miles northwest of New Union Church and about 300 feet south and 100 feet west of a stream crossing at Brush Creek. NW1/4, NW1/4, Sec. 15, T. 7 S.,
R. 15 W.

RANGE IN CHARACTERISTICS: Iuka soils are very strongly or strongly acid throughout, except for surface has been limed. Clay content of the 10 to 40-inch control section is 10 to 18 percent. Some pedons have thin gravelly or sandy strata and some pedons have textures of sandy clay loam or clay loam at depths below 40 inches. Thin bedding planes of contrasting textures are common throughout in most pedons.

The A or Ap horizon has hue of 10YR or 7.5YR, value of 4 to 7, and chroma 2 to 4. Texture is loamy sand, fine sandy loam, sandy loam, silt loam or loam.

The C horizon has hue of 7.5YR to 2.5Y, value of 4 to 6, and chroma of 3 to 6. Redoximorphic depletions in shades of gray range from few to many and are within 20 inches of the surface. Texture is sandy loam, fine sandy loam, loam, silt loam and below 38 inches, sandy clay loam.

The Cg horizon has hue of 7.5YR to 5Y, value of 4 to 6, and chroma of 1 or 2. Redoximorphic features in shades of red, yellow, gray and brown range from few to many. A few flakes of mica and soft dark colored bodies or fine black and brown concretions are in some pedons. Some pedons have buried A horizons at depths below 20 inches. Many pedons have no dominant matrix color and they are multicolored in shades of yellow, gray, brown and red. Texture is loamy sand, sandy loam, fine sandy loam, loam, silt loam or sandy clay loam.

COMPETING SERIES: There are no competing series in the same family. Closely related series include the Collins and Ochlockonee series. Collins soils are on similar positions in the southern Mississippi valley silty uplands (MLRA 134) and have coarse-silty control sections with mixed mineralogy. The well drained Ochlocknee series is on slightly higher bench and natural levee positions alongside stream channels.

GEOGRAPHIC SETTING: Iuka soils are on nearly level flood plains. They formed in sandy or loamy alluvium commonly 6 or more feet thick. The climate is humid subtropical. Slopes range from 0 to 2 percent Near the type location the average daily temperature for January is 42 degrees F., the average daily temperature for July is 79 degrees F., the mean annual temperature is about 61 degrees F., and the mean annual precipitation is about 54 inches.

GEOGRAPHICALLY ASSOCIATED SOILS: These include competing Ochlockonee series along with the Bibb, Cahaba, Kalmia, Kirkville, Mantachie and Mooreville series. The poorly drained Bibb soils are on lower positions. The well drained Cahaba and Kalmia soils are on adjacent terrace positions that rarely flood, have argillic horizons, fine-loamy control sections. Kirkville soils are on similar positions but have cambic horizons. The somewhat poorly drained Mantachie soils are on slightly lower positions, have cambic horizons and have fine-loamy control sections. Mooreville soils are on similar positions, have cambic horizons and have fine-loamy control sections.

DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; moderate permeability.

USE AND VEGETATION: Most areas of Iuka soils are in woodland. Some areas have been cleared and cultivated to corn, soybeans, small grains and truck crops. Many areas are used for hay production or pasture. The native vegetation consists of forest of water oak, willow, beech, sweetgum, hickory, maple, ironwood, eastern cottonwood, alder, white oak, and in some places, pine.

DISTRIBUTION AND EXTENT: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and possibly Kentucky and Virginia. The series is of large extent.


SERIES ESTABLISHED: Tishomingo County, Mississippi; 1938.

REMARKS: Diagnostic horizons and features recognized in this pedon:

Ochric epipedon - the zone from 0 to 13 inches (Ap and A horizons).

Aquic feature - a seasonal high water table at a 13-inch depth.

Iuka soils are rarely to commonly flooded. A water table is at depths of 12 or more inches, and the soil is commonly saturated with water between 12 and 40 inches during some season of most years.

ADDITIONAL DATA: Laboratory data is available on the National Soil Survey website at: http://ncsslabdatamart.sc.egov.usda.gov/querypage.aspx

Laboratory data was provided by Auburn University, Soil Characterization Laboratory, Auburn AL and the National Soil Survey Laboratory, Lincoln, NE.

National Cooperative Soil Survey