LOCATION PORTLAND AR+LA

Established Series
LBW; Rev. JDS
12/2018

PORTLAND SERIES

The Portland series consists of very deep, somewhat poorly drained, very slowly permeable soils that formed in clayey alluvium from Permian geological formations. These level to nearly level soils are on flood plains and slack water areas along the Arkansas and Red Rivers and their former channels. Slopes range from 0 to 3 percent.

TAXONOMIC CLASS: Very-fine, mixed, superactive, nonacid, thermic Vertic Epiaquepts

TYPICAL PEDON: Portland silty clay, 1 percent slope, cultivated.(Colors are for moist soil, unless otherwise stated.)

Ap1--0 to 3 inches; dark grayish brown (10YR 4/2) silty clay; few fine faint grayish brown and yellowish brown iron accumulations; moderate fine angular blocky structure; firm; sticky, plastic; common fine roots; strongly acid; abrupt wavy boundary. (2 to 10 inches thick)

Ap2--3 to 8 inches; brown (7.5YR 4/4) clay; common medium distinct grayish brown (10YR 5/2) iron depletions; moderate fine angular blocky structure; firm, sticky, plastic; common fine roots; very strongly acid; clear wavy boundary. (0 to 7 inches thick)

Bw1--8 to 18 inches; reddish brown (5YR 4/4) clay; common medium prominent grayish brown (10YR 5/2) iron depletions; strong fine angular blocky structure; very firm, very sticky, very plastic; common fine roots; few fine pores; few slickensides that do not intersect; shiny faces on peds; very strongly acid; gradual wavy boundary.

Bw2--18 to 30 inches; reddish brown (5YR 4/4) clay; common medium distinct dark brown (10YR 3/3) organic coatings; moderate fine angular blocky structure; very firm, very plastic; common fine roots; few fine pores; few slickensides that do not intersect; shiny faces on peds; moderately acid; clear wavy boundary.

Bw3--30 to 45 inches; reddish brown (5YR 4/3) clay; strong fine angular blocky structure; very firm, very plastic; few fine roots; common slickensides 4 to 6 inches wide that do not intersect; smooth shiny faces on peds; slightly alkaline; calcareous; clear wavy boundary. (Combined thickness of the Bw horizon ranges from 38 to 53 inches.)

C--45 to 72 inches; alternating 1 to 6 inch layers of reddish brown (5YR 4/3) silty clay and brown (7.5YR 4/4) silt loam; massive; silty clay is firm, silt loam is friable; few carbonate concretions; moderately alkaline; calcareous.

TYPE LOCATION: Ashley County, Arkansas; 1 1/2 miles west of Montrose; 300 feet south of U. S. Highway 82; SW1/4NW1/4NE1/4, sec. 24, T. 16 S., R. 4
W.

RANGE IN CHARACTERISTICS: Solum thickness is more than 40 inches. Reaction is strongly acid or very strongly acid in the A horizon, except where limed, and ranges from very strongly acid to slightly acid in the Bw1 horizon. The lower Bw and C horizons range from slightly acid through moderately alkaline. Some pedons may be calcareous below depth of 30 inches and contain hard carbonate concretions.

The A or Ap horizon has hue of 10YR, value of 3, 4, or 5, and chroma of 2 or 3 or hue of 7.5YR, value of 3 or 4 and chroma of 2 or 4. Iron depletions are in shades of gray and iron accumulations are in shades of brown. Texture is silty clay or clay, but may be silty clay loam or silt loam in areas with thin layers of recent overwash.

The B horizon has hue of 5YR, value of 4 and chroma of 3 or 4, or hue of 7.5YR, value of 4 or 5, and chroma of 4. Iron depletions are in shades of gray and iron accumulations are in shades of brown. Texture is commonly clay, but thin subhorizons may be silty clay. The weighted average clay content of the 10-40 inch control section ranges from 60 to 85 percent.

The C horizon has colors similar to the Bw. Texture ranges from silt loam to clay. The C horizon is often stratified.

COMPETING SERIES: There are no other series in the same family. Series in closely related families include Alligator, Gladewater, Harahan, Jacob, Kobel, Leeper, Openlake, Perry, and Sharkey. Alligator soils are in a smectitic mineralogy class and are acid. Gladewater, Kobel, Leeper, and Openlake soils are in a fine particle size class and a smectitic mineralogy class. Harahan, Perry, and Sharkey soils are in a smectitic mineralogy class and are acid. Jacob soils are in a smectitic mineralogy class, are acid, and have a mean soil temperature of less than 59 degrees F.

GEOGRAPHIC SETTING: Portland soils are on level to nearly level flood plains and slack water areas along the Arkansas and Red Rivers and their former channels. These soils formed in clayey alluvium from Permian geological formations. Slopes range from 1 to 3 percent. The mean annual temperature is about 65
degrees F and the mean annual precipitation is about 51 inches near the type location.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Perry soils and the Hebert, McGehee, Rilla, and Yorktown series. Hebert and Rilla soils, which occur on low natural levees adjacent to Portland are in a fine-silty particle size class and are more acid in the lower part of the subsoil. McGehee soils, which occur in ridge-swale areas adjacent to Portland soils are in a fine-silty particle size class and are more acid in the lower part of the subsoil. Yorktown soils, which occur in ponded backswamp areas are grayer and do not have vertic properties.

DRAINAGE AND PERMEABILITY: Somewhat poorly drained; runoff is slow; very slow permeability. These soils have a seasonal high water table that is within 12 inches of the soil surface from December through May. Most areas are subject to flooding unless protected by levees.

USE AND VEGETATION: Most areas are cultivated. Principal crops include rice, soybeans, cotton, and grain sorghum. Native vegetation was sweetgum, water tupelo, water tolerant oaks, bald cypress, hackberry, and hawthorne.

DISTRIBUTION AND EXTENT: Flood plains and slack water areas along the Arkansas River, Red River, and their abandoned channel in Arkansas, Oklahoma, and Texas. The series is of moderate extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: TEMPLE, TEXAS

SERIES ESTABLISHED: Ashley County, Arkansas; 1913.

REMARKS: The series was reclassified to an Epiaquept (was a Haplaquept) and was assigned to a superactive activity class in 5/2001 based on data from the type location pedon. Diagnostic horizons and features recognized in the pedon:

Ochric epipedon - The zone from the soil surface to a depth of 8 inches.

Cambic horizon - The zone from 8 to 45 inches.

The classification of this soil is based on the presence of an aquic moisture regime and because of red parent material that remains red after citrate dithionite extraction.

ADDITIONAL DATA: Characterization of the type location by the Soil Survey Laboratory, Lincoln, Nebraska. Pedon No. S60AR-002-001.

National Cooperative Soil Survey
U.S.A.