LOCATION ATWOOD MSEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, semiactive, thermic Typic Paleudalfs
TYPICAL PEDON: Atwood silt loam - cultivated.
(Colors are for moist soil unless otherwise stated.)
Ap--0 to 6 inches, dark brown (7.5YR 4/4) silt loam; weak fine and medium granular structure; friable; common fine roots; few worm casts, some material from B horizon as fillings in worm holes and root channels; neutral; abrupt smooth boundary. (4 to 9 inches thick)
Bt1--6 to 18 inches, dark reddish brown (5YR 3/4) silty clay loam; moderate fine and medium subangular blocky structure; friable, slightly plastic; few fine roots; few fine black concretions; few root channels filled with material from Ap horizon; patchy clay films on faces of peds and in root channels; slightly acid; gradual smooth boundary.
Bt2--18 to 31 inches, dark reddish brown (2.5YR 3/4) silty clay loam; moderate medium and coarse subangular and angular blocky structure; friable, slightly plastic; few fine roots; common fine and coarse black coatings; many fine black concretions; clay films on faces of peds and lining pores; few root channels and worm holes filled with material from Ap horizon; slightly acid; gradual smooth boundary.
Bt3--31 to 45 inches, dark reddish brown (2.5YR 3/4) silty clay loam; moderate medium and coarse subangular and angular blocky structure; friable, slightly plastic; few fine roots; common fine to coarse black coatings; common fine black concretions; clay films on faces of peds and lining pores; few root channels filled with material from Ap horizon; slightly acid; gradual smooth boundary.
Bt4--45 to 57 inches, dark reddish brown (2.5YR 3/4) silty clay loam; moderate medium and coarse subangular and angular blocky structure; friable, slightly plastic; few fine roots; common fine black concretions; clay films on faces of peds and in pores; strongly acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 34 to 60 inches or more.)
2Bt--57 to 79 inches, dark red (10YR 3/6) clay loam; moderate medium and coarse subangular and angular blocky structure; friable, slightly plastic; few fine black coatings; few concretions; patchy clay films on faces of peds and in pores; slightly acid.
TYPE LOCATION: Pontotoc County, Mississippi; 2-1/2 miles south of Pontotoc, on Mississippi State Highway No. 15, then 1/4 mile southwest on gravel road, then 200 yards west of gravel road SW1/4NE1/4 sec. 17, T. 10 S., R. 3 E.
RANGE IN CHARACTERISTICS: The solum ranges from 60 to more than 80 inches thick. It is strongly acid to slightly acid, except for surface layers in areas that have been limed.
The A horizon has hue of 10YR, 7.5YR, or 5YR, value of 4 or 5, and chroma of 2 to 4. It is loam or silt loam.
The Bt horizon has hue of 5YR or 2.5YR, value of 3 to 5, and chroma of 3 to 6. It is silty clay loam that increases in sand in the lower part. The upper 20 inches of the Bt horizon has 27 to 35 percent clay.
The 2Bt horizon has hue of 10R, 2.5YR, or 5YR, value of 3 to 5, and chroma of 4 to 6. It is clay loam, sandy clay loam, or silty clay loam. Black coatings and concretions are few to common in the Bt and 2Bt horizons.
COMPETING SERIES: The Lexington is the only competing series in the same family. Closely related series are the Greenville, Lucedale, Macon, Memphis, Providence, Sallisaw, and Tippah. Lexington soils have a bisequum, and the amount of clay decreases with depth, and the 2Bt horizon is sandy loam or loam. Greenville and Lucedale soils have an A horizon with moist color value of less than 4. Also Greenville, soils are clayey in the particle-size control section. Lucedale, Macon, and Sallisaw soils are fine-loamy in the particle-size control section. Memphis soils have a solum that is less than 60 inches thick and the sand content is less than 5 percent to a depth of 48 inches. Providence soils are moderately well drained and have a fragipan. Tippah soils have mottles with chroma of 2 or less within a depth of 30 inches of the surface.
GEOGRAPHIC SETTING: Atwood soils are on uplands and stream terraces of low relief in the Southern Mississippi Valley Silty Uplands. Slopes range from 0 to 17 percent. The Atwood soils formed in a mantle on silty material and underlying loamy material. The mean annual temperature is 62 degrees F., and mean annual precipitation is 47.6 inches near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lexington and Providence soils of the competing series and the Adaton, Bude, Henry, Ora, Ruston and Smithdale soils. The well drained Lexington and moderately well drained Providence soils are in similar positions as the Atwood soils. Poorly drained Adaton and Henry soils, which are in depressions and broad drainageways, have dominant low chroma color below the A horizon; in addition, the Henry soils have a fragipan. The somewhat poorly drained Bude soils, which are near heads of drainageways and in broad depressions, have low chroma mottles within 16 inches of the surface and have a fragipan. The moderately well drained Ora soils, which are on ridgetops, have a fragipan and a fine-loamy particle-size class. The well drained Ruston soils, which have a bisequum and are in a fine-loamy particle-class, are on ridgetops. The well drained Smithdale soils, which have a fine-loamy particle-size class, are on hillsides.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderate permeability.
USE AND VEGETATION: Most areas of this soil are cleared and used for cotton, soybeans, corn, and peach orchards. Some areas of the soil are used for hay and pasture. The natural vegetation is a mixed forests of hardwoods and pines. Common trees are cherrybark oak, white oak, sweetgum, loblolly pine.
DISTRIBUTION AND EXTENT: Mississippi. This soil is of moderate extent.
MLRA OFFICE RESPONSIBLE: Little Rock, Arkansas
SERIES ESTABLISHED: Franklin County, Alabama; 1927.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface of the soil to a depth
of approximately 6 inches (Ap horizon).
Argillic horizon - the zone from approximately 6 to 79 inches
(Bt1, Bt2, Bt3, Bt4, 2Bt).