LOCATION TAMALCO ILEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Natrudalfs
TYPICAL PEDON: Tamalco silt loam - on a north-facing slope of about 3 percent in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 6 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; moderate fine granular structure; friable; very strongly acid; abrupt smooth boundary. (6 to 9 inches thick)
E--6 to 9 inches; brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; few fine prominent reddish brown (2.5YR 4/4) mottles; weak thin platy structure; friable; very strongly acid; abrupt smooth boundary. (3 to 6 inches thick)
B/E--9 to 11 inches; brown (10YR 5/3) silty clay loam (B), and many prominent gray (10YR 6/1) silt coatings on faces of peds and as fillings between peds, light gray (10YR 7/1) dry (E); common prominent reddish brown (2.5YR 4/4) mottles; moderate medium subangular blocky structure; firm; very strongly acid; abrupt smooth boundary. (0 to 3 inches thick)
Bt1--11 to 17 inches; reddish brown (5YR 4/4) silty clay; moderate medium prismatic structure parting to moderate fine angular blocky; firm; common distinct dark brown (7.5YR 3/2) clay films on faces of peds; strongly acid; clear smooth boundary.
Bt2--17 to 28 inches; pale brown (10YR 6/3) silty clay loam; few fine faint light brownish gray (10YR 6/2), many fine faint brown (10YR 5/3), and few fine distinct yellowish brown (10YR 5/6) mottles; weak fine and medium angular blocky structure; firm; common distinct very dark grayish brown (10YR 3/2) clay films on faces of peds and fillings in root channels; common medium white concretions (calcium carbonates) strong effervescence of the concretions; mildly alkaline; clear smooth boundary.
Bt3--28 to 35 inches; gray (10YR 6/1) silt loam; many medium distinct yellowish brown (10YR 5/6) mottles; weak coarse angular blocky structure; firm; few distinct grayish brown (10YR 5/2) clay films on faces of peds; few fine black accumulations (iron and manganese oxides); few medium white concretions (calcium carbonate); strong effervescence of the concretions; moderately alkaline; clear smooth boundary. (Combined thickness of the Bt horizons is 15 to 40 inches.
BC--35 to 42 inches; light brownish gray (10YR 6/2) silt loam; many fine prominent strong brown (7.5YR 5/6) mottles; weak coarse subangular blocky structure; friable; few fine black accumulations (iron and manganese oxides) about 5 percent sand; moderately alkaline; gradual smooth boundary. (0 to 18 inches thick)
2C1--42 to 54 inches; grayish brown (10YR 5/2) silt loam; many medium distinct dark brown (7.5YR 4/4) mottles; massive; friable; few fine black accumulations (iron and manganese oxides) about 15 to 20 percent sand; moderately alkaline; gradual smooth boundary. (0 to 20 inches thick)
2C2--54 to 60 inches; dark brown (7.5YR 4/4) silt loam; common medium distinct dark grayish brown (10YR 4/2) mottles; massive, firm; few fine black accumulations (iron and manganese oxides) about 25 percent sand; moderately alkaline.
TYPE LOCATION: Montgomery County, Illinois; about 3 miles north and 0.5 mile west of Hillsboro; 2300 feet west and 78 feet south of the northeast corner of sec 26, T. 9 N., R. 4 W.
RANGE IN CHARACTERISTICS: The solum is 36 to 60 inches in thickness. A concentration of exchangeable sodium of 15 percent or more typically is at depths of 12 to 24 inches, but in some pedons it is as deep as 30 inches below the soil surface. The control section averages between 35 and 42 percent clay, but individual subhorizons contain as much as 45 percent.
The Ap or A horizon typically has hue of 10YR, value of 3 through 5, and chroma of 2 or 3. Some pedons that are eroded have hue of 7.5YR, value of 4 or 5, and chroma of 2 through 6. Eroded pedons are silt loam or silty clay loam. The Ap or A horizon is very strongly acid to slightly acid, but is neutral or mildly alkaline in some pedons that have been limed.
The E horizon has hue of 10YR, value of 4 through 6, and chroma of 2 or 3. It is very strongly acid to neutral. Some pedons that are eroded or have been plowed deep lack an E horizon.
The upper part of the Bt horizon has hue of 7.5YR or 5YR, value of 4 or 5, and chroma typically of 4 but ranging from 3 through 8. Some pedons contain high chroma mottles. The upper part of the Bt horizon is silty clay or silty clay loam. It is very strongly acid to neutral.
The lower part of the Bt horizon has hue of 10YR or 2.5Y, value of 5 or 6, and chroma of 1 through 4. It is silty clay loam in the upper part and typically has decreasing clay content with increasing depth. It typically is moderately alkaline to neutral but ranges to strongly acid in the upper part in some pedons.
The BC horizon has hue of 7.5YR, 10YR, or 2.5Y; value of 4 through 6; and chroma of 2 through 6, and is mottled. It is silt loam or silty clay loam. It is mildly alkaline through strongly alkaline. Some pedons contain free carbonates or calcium carbonate concretions.
Some pedons have a 2BC horizon below a depth of 40 inches. It is silty clay loam, silt loam, loam or clay loam. It is moderately alkaline or strongly alkaline. Some pedons contain free carbonates or calcium carbonate concretions.
The C or 2C horizon has hue of 7.5YR, 10YR, or 2.5Y; value of 4 through 6; and chroma of 2 through 6. It is silt loam, loam, silty clay loam or clay loam. It is mildly alkaline through strongly alkaline.
COMPETING SERIES: This is the only series in the family. Series in closely related families are the Coulterville, Darmstadt, Grantfork, Piasa and Stuttgart. Coulterville and Grantfork soils contain less than 15 percent exchangeable sodium in all parts between depths of 10 and 40 inches. Darmstadt soils are fine-silty and have an aquic soil moisture regime. Piasa soils have color value of 2 or 3 in the Ap or A horizon and have an aquic moisture regime. Stuttgart soils are thermic.
GEOGRAPHIC SETTING: Tamalco soils are on convex crests and sideslopes of ridges and on sideslopes of drainageways on the loess covered Illinoian till plain. Slope gradients are 1 to 7 percent. Tamalco soils typically formed in loess, but some pedons formed in loess and the underlying loamy or silty deposits. The loamy or silty deposits are early Wisconsinan Roxana silt. Tamalco soils are underlain, at a depth of 4 to 6 feet, by a strongly developed paleosol in Illinoian till. The buried soil may or may not have been truncated by erosion prior to loess deposition. Mean annual temperature varies from 53 to 56 degrees F, and mean annual precipitation varies from 36 to 42 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Darmstadt and Piasa soils and the Cisne, Cowden, Hoyleton, Huey, Oconee, and Richview soils. The somewhat poorly drained Darmstadt soils are on broader or lower convex ridges or on similar sideslopes nearby. The poorly drained Piasa soils are on broad plains nearby and generally farther from the drainageways. Cisne, Cowden, and Huey soils are all poorly drained and are on broad, nearly level plains. In addition Cisne and Cowden soils have very low concentrations of exchangeable sodium in their subsoil. The somewhat poorly drained Hoyleton and Oconee soils are on lower convex ridges or broader interstream areas, and do not have natric horizons. The moderately well drained and well drained Richview soils do not have a natric horizon and are on slightly higher convex ridges nearby.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is medium. Permeability is very slow.
USE AND VEGETATION: Most areas of Tamalco soils are cultivated. Corn, soybeans, and small grain are the principal crops. Native vegetation was hardwood trees.
DISTRIBUTION AND EXTENT: Southern Illinois. Tamalco soils are moderately extensive.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Montgomery County, Illinois, 1968.
REMARKS: This pedon is used to represent the central concept of Typic Natrudalfs in Soil Taxonomy.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - zone from the surface of the soil to a depth of 9 inches (Ap and E horizons); argillic horizon - the zone from about 9 to 28 inches (B/E, Bt1, and Bt2 horizons); natric horizon.
The B/E horizon meets the criteria of more than 1.2 increase in clay content, but has no translocated clay described; the Bt3 horizon may not be part of the argillic horizon because it decreases to less than 1.2 ratio of clay content, although it has translocated clay described.
ADDITIONAL DATA: Data for the typical pedon was published in the Soil Survey of Montgomery County, Illinois.