LOCATION MARTINSBURG IAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Hapludalfs
TYPICAL PEDON: Martinsburg silt loam on a northeast-facing foot slope of 3 percent gradient - cultivated. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 6 inches; dark grayish brown (10YR 4/2) silt loam (21 percent clay), pale brown (10YR 6/3) dry; weak medium platy structure parting to weak fine granular; friable; few faint light gray (10YR 7/2) dry silt coatings on faces of peds; moderately acid; abrupt smooth boundary. (6 to 9 inches thick)
E1--6 to 13 inches; brown (10YR 4/3) and yellowish brown (10YR 5/4) silt loam (21 percent clay); weak medium platy and weak fine subangular blocky structure; friable; many distinct white (10YR 8/1) dry silt coatings on faces of peds; few dark concretions (iron and manganese oxides); moderately acid; gradual smooth boundary.
E2--13 to 20 inches; brown (10YR 4/3) silt loam (23 percent clay); weak fine subangular blocky structure; friable; many distinct white (10YR 8/1) dry silt coatings on faces of peds; moderately acid; gradual smooth boundary. (Combined thickness of the E horizons is 12 to 20 inches.)
Bt1--20 to 27 inches; dark yellowish brown (10YR 4/4) silty clay loam (28 percent clay); brown (10YR 4/3) coatings on faces of peds; weak medium prismatic structure parting to weak fine subangular blocky; friable; few faint dark brown (10YR 3/3) clay films and few distinct white (10YR 8/1) dry silt coatings on faces of peds; strongly acid; clear smooth boundary.
Bt3--27 to 34 inches; yellowish brown (10YR 5/4) silty clay loam (31 percent clay); brown (10YR 4/3) coatings on faces of peds; weak medium prismatic structure parting to weak fine subangular blocky; friable; few faint dark brown (10YR 3/3) and few distinct light gray (10YR 7/2) dry silt coatings on faces of peds; strongly acid; gradual smooth boundary.
Bt3--34 to 41 inches; yellowish brown (10YR 5/4) silty clay loam (34 percent clay); dark yellowish brown (10YR 4/4) coatings on faces of peds; few fine faint yellowish brown (10YR 5/8) and few fine distinct light brownish gray (2.5Y 6/2) mottles; weak medium prismatic structure parting to weak fine subangular blocky; friable; few faint dark brown (10YR 3/3) clay films and light gray (10YR 7/2) silt coatings on faces of peds; few dark concretions (iron and manganese oxides); strongly acid; gradual smooth boundary.
Bt4--41 to 57 inches; yellowish brown (10YR 5/4) silty clay loam (32 percent clay); dark yellowish brown (10YR 4/4) coatings on faces of peds; few fine distinct strong brown (7.5YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak medium prismatic structure parting to weak fine subangular blocky; friable; few faint dark brown (10YR 3/3) clay films on prisms and in old pores; few dark concretions (iron and manganese oxides); strongly acid; gradual smooth boundary. (Combined thickness of the Bt horizons is 30 to 48 inches.)
BC--57 to 60 inches; yellowish brown (10YR 5/4) and brown (10YR 5/3) silty clay loam (30 percent clay); few fine faint yellowish brown (10YR 5/8) and common fine distinct light brownish gray (2.5Y 6/2) mottles; weak coarse prismatic structure; friable; few faint dark brown (10YR 3/3) clay films and light gray (10YR 7/2) silt coatings on faces of prisms; common dark concretions (iron and manganese oxides); strongly acid.
TYPE LOCATION: Keokuk County, Iowa; about 1 mile south and 3 miles west of Delta; 1300 feet east and 2550 feet north of the southwest corner of sec. 8, T. 75 N., R. 13 W.
RANGE IN CHARACTERISTICS: The solum typically is more than 60 inches thick but ranges from about 48 to 90 inches in thickness. Carbonates are absent in the solum. The solum is medium acid or strongly acid in the most acid part.
The Ap or A horizon is dark grayish brown (10YR 4/2) or brown (10YR 4/3). Some pedons have very dark grayish brown (10YR 3/2) or dark brown (10YR 3/3) coatings on faces of peds. The A horizon is silt loam with about 20 to 24 percent clay.
The E horizon has hue of 10YR, value of 4 or 5, and chroma of 3 or 4. It is silt loam with about 18 to 24 percent clay.
A BE horizon is in some pedons.
The Bt horizon has hue of 10YR, value of 4 or 5, and chroma of 3, 4, or 6. It is silty clay loam with a clay content of 27 to 35 percent. The depth to the layer of maximum clay content is between 30 and 36 inches in most pedons. Few or common mottles of low and high chroma are in the lower part of the Bt horizon and BC horizon in most pedons.
COMPETING SERIES: These are the Alford, Baraboo, Bertrand, Birkbeck, Black-hammer, Cadiz, Camden, Dodge, Dubuque, Elco, Eleroy, Fayette, Flagg, Hackers, Inton, Iona, Jackson, Knowles, LaFarge, Lomira, Marseilles, Mayville, Menfro, Mentor, Middletown, Minnith, Palsgrove, Rozetta, Rush, Russell, Seaton, St. Charles, Sylvan, Uniontown, Weingarten, Westmore, Winfield, and Zurich series in the same family. Alford, Birkbeck, Fayette, Inton, Iona, Menfro, Rozetta, Seaton, St. Charles, and Winfield soils all formed in loess, have thinner E horizons, and are not so deep to the clay maximum. Baraboo, Blackhammer, Dubuque, Knowles, La Farge, and Marseilles soils have bedrock within depths of 40 inches. Bertrand, Jackson, and Middletown soils have more sand and less clay in the lower parts of the sola. Blackhammer, Cadiz, Camden, Dodge, Elco, Lomira, Mayville, Minnith, Rush, Russell, and Zurich soils have 2Bt horizons and more sand in the lower part of the solum. Eleroy, Palsgrove, and Weingarten soils have finer textures in the lower part of the solum. Flagg and Hackers soils have redder hue in the lower part of the solum. Mentor soils have stratification in the lower parts of the solum. Sylvan and Uniontown soils have thinner solum. Westmore soils have shale and sandstone fragments at depths of less than 40 inches.
GEOGRAPHIC SETTING: Martinsburg soils are on plane or slightly concave foot slopes of 2 to 9 percent gradient. They formed in oxidized and leached silty colluvium from adjacent loess uplands. Total sand content typically is less than 15 percent, and most is fine and very fine in size. Mean annual temperature ranges from about 48 to 52 degrees F, and mean annual precipitation ranges from about 32 to 36 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Fayette soils and the Clinton, Coppock, Lindley, and Vesser soils. Fayette and Clinton soils are on ridges and side slopes upslope. Clinton soils have a thinner E horizon and higher clay content in the Bt horizon. Coppock and Vesser soils are on similar landscape positions but have a grayer B horizon. Vesser soils also have mollic epipedons. Lindley soils are on side slopes upslope and have more sand and coarse fragments in the Bt horizon.
DRAINAGE AND PERMEABILITY: Well or moderately well drained. Surface runoff is medium. Permeability is moderate.
USE AND VEGETATION: Commonly cropped to corn, soybeans, small grain, and legume hays. Native vegetation was deciduous trees (oak hickory).
DISTRIBUTION AND EXTENT: South central and southeastern Iowa and possibly northeastern Missouri. Martinsburg soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Keokuk County, Iowa, 1974.
REMARKS: Diagnostic horizons and features recognized in this pedon are: ochric epipedon--the zone from the surface to a depth of approximately 20 inches (A and E horizons); argillic horizon--the zone from approximately 20 to 57 inches (Bt1, Bt2, Bt3, and Bt4 horizons); a udic soil moisture regime.