LOCATION ARMISTEAD LAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, thermic Aquic Argiudolls
TYPICAL PEDON: Armistead clay in a cultivated field.
(Colors are for moist soil unless otherwise stated.)
Ap--0 to 7 inches; dark reddish brown (5YR 3/3) clay; weak medium subangular blocky structure; firm; common medium roots; mildly alkaline; abrupt smooth boundary. (4 to 10 inches thick)
A--7 to 13 inches; dark reddish brown (5YR 3/3) clay; moderate coarse prismatic structure; firm; common fine roots; mildly alkaline; clear smooth boundary. (6 to 10 inches thick)
2A--13 to 21 inches; very dark gray (5YR 3/1) silty clay loam; few fine faint gray and dark gray mottles; moderate medium subangular blocky structure; firm; common fine roots; common pores; (5YR 3/3) clay films on vertical faces of some peds; mildly alkaline; gradual smooth boundary. (6 to 12 inches thick)
2Bt1--21 to 33 inches; yellowish red (5YR 5/6) silt loam; weak coarse prismatic structure that parts to moderate coarse subangular blocky; friable; common fine roots, common pores; dark (5YR 3/1) stains in pores and root channels; continuous clay films on peds; mildly alkaline; clear wavy boundary. (8 to 15 inches thick)
2Bt2--33 to 54 inches; yellowish red (5YR 5/6) silt loam; moderate medium subangular blocky structure; friable; common pores, common fine roots; (5YR 3/1) dark stains along root channels; discontinuous clay films; mildly alkaline; clear wavy boundary. (10 to 25 inches thick)
2C--54 to 62 inches; yellowish red (5YR 5/6) silt loam; massive; friable; common fine pores, few fine roots; common medium calcium carbonate concretions, few fine black accretions; pockets and streaks of light reddish brown (5YR 6/3) silt loam; moderately alkaline; calcareous.
TYPE LOCATION: Red River Parish, Louisiaa; 6,200 feet west of Williams, Louisiana; 960 feet north from center of south section line; 1,560 feet west from local road; sec. 16, T. 14 N., R. 12 E.
RANGE IN CHARACTERISTICS: Solum is from about 40 to 70 inches thick.
The Ap or the A horizon is silty clay or clay. It is dark reddish brown (5YR 2/2, 3/2, 3/3), dusky red (2.5YR 3/2), or dark brown (7.5YR 3/2). It is slightly acid to moderately alkaline.
The 2A horizon is very dark gray (5YR 3/1), dusky red (2.5YR 3/2), dark reddish brown (5YR 3/2, 3/3), or dark brown (7.5YR 3/2) and is mottled with grayer colors. It is silt loam or silty clay loam and neutral to moderately alkaline.
The 2Bt horizon is yellowish red (5YR 4/6, 4/8, 5/6, 5/8), reddish brown (5YR 4/4, 5/4), red (2.5YR 4/6), or reddish brown (2.5YR 4/4, 5/4). It is silty clay loam or silt loam and averages between 18 and 30 percent clay. The 2Bt horizon is slightly acid to moderately alkaline.
The 2C horizon has colosr in shades of brown or red. Reaction ranges from neutral to moderately alkaline and is calcareous in some pedons. Texture is variable and ranges from very fine sandy loam to clay.
COMPETING SERIES: These are the Ashwood, Benklin, Buxin, Caspiana, Desha, Latanier, Mason, Moreland, Mer Rouge, Pledger, Roebuck, Reelfoot, and Tiptonville series. Ashwood, Buxin, Desha, Moreland, Pledger, and Roebuck soils are clayey to depths of 40 inches or more. Benklin soils have hues of 7.5YR or yellower below the mollic epipedon. Caspiana, Mason, Mer Rouge, Reelfoot, and Tiptonville soils lack clayey horizons in the 10 to 20 inch section. Latanier soils lack argillic horizons and have 20 to 36 inches of clayey material over loamy IIC horizons.
GEOGRAPHIC SETTING: Armistead soils occur on level to very gently sloping alluvial plains. They formed in reddish clayey over loamy alluvium on bottomlands of the Red River. The climate is warm and humid. Mean annual rainfall ranges from 38 to 60 inches and mean annual temperature ranges from 57 degrees to 66 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: This includes the competing Caspiana and Moreland series and the Gallion series. Caspiana and Gallion soils are loamy throughout.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; slow permeability in the upper horizons and moderately slow permeabiliy in lower horizons.
USE AND VEGETATION: Areas protected by levees have been cleared and are used for cotton, soybeans, small grain, hay, and pasture. Native vegetation is mixed hardwoods, cottonwood, cherrybark oak, water oak, sweetgum, pecan, sycamore, green ash, and hackberry.
DISTRIBUTION AND EXTENT: Louisiana and possibly Arkansas, Oklahoma, and Texas. This series is of minor extent.
MLRA OFFICE RESPONSIBLE: Little Rock, Arkansas
SERIES ESTABLISHED: Red River Parish, Louisiana; 1973.
REMARKS: These soils were formerly classified in the Alluvial great soil group. These soils are considered to have argillic horizons, though the 2Bt horizons do not have the required clay increase for an argillic horizon. The higher clay content in the 2A horizon is due to mixing with the overwash clay A horizon.