LOCATION DARMSTADT ILEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Aquic Natrudalfs
TYPICAL PEDON: Darmstadt silt loam--on a nearly level summit in a cultivated field at an elevation of about 470 feet above mean sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; dark grayish brown (10YR 4/2) silt loam, light brownish gray (10YR 6/2) dry; weak thick platy structure parting to weak very fine granular; friable; many very fine roots; few fine continuous tubular pores; few fine rounded black (10YR 2/1) iron-manganese nodules with sharp boundaries throughout; 1 percent exchangeable sodium; neutral; abrupt smooth boundary. (5 to 9 inches thick)
E--8 to 11 inches; light brownish gray (10YR 6/2) and grayish brown (10YR 5/2) silt loam, light gray (10YR 7/2) dry; weak thick platy structure parting to weak fine subangular blocky; friable; common very fine roots; few fine constricted tubular pores; many fine and medium rounded black (10YR 2/1) iron-manganese nodules with sharp boundaries throughout; 4 percent exchangeable sodium; neutral; abrupt smooth boundary. (3 to 10 inches thick)
Btn1--11 to 16 inches; brown (10YR 5/3) silty clay loam; weak medium prismatic structure parting to moderate fine and medium angular blocky; firm; many very fine roots; few faint grayish brown (10YR 5/2) clay films on faces of peds; common medium faint grayish brown (10YR 5/2) iron depletions and common medium prominent yellowish brown (10YR 5/8) masses of iron accumulation in the matrix; few fine irregular strong brown (7.5YR 5/6) masses of iron-manganese accumulation; and few medium rounded black (7.5YR 2.5/1) iron-manganese nodules with clear strong brown (7.5YR 4/6) boundaries ; 7 percent exchangeable sodium; very strongly acid; gradual smooth boundary.
Btn2--16 to 21 inches; pale brown (10YR 6/3) silty clay loam; moderate medium prismatic structure parting to strong medium angular blocky; firm; common very fine roots; common distinct gray (10YR 5/1) clay films on faces of peds; many fine faint grayish brown (10YR 5/2) iron depletions, and many fine distinct brownish yellow (10YR 6/6) and many fine prominent yellowish brown (10YR 5/8) masses of iron accumulation in the matrix; few fine irregular strong brown (7.5YR 5/6) masses of iron-manganese accumulation and few medium rounded black (7.5YR 2.5/1) iron-manganese nodules with clear boundaries and strong brown (7.5YR 4/6) surfaces throughout; 12 percent exchangeable sodium; moderately acid; gradual smooth boundary.
Btn3--21 to 27 inches; pale brown (10YR 6/3) and light brownish gray (10YR 6/2) silty clay loam; moderate coarse prismatic structure; firm; few very fine roots; few distinct gray (10YR 5/1) clay films on faces of peds; many coarse prominent strong brown (7.5YR 5/8) masses of iron accumulation in the matrix; few medium irregular very dark brown (7.5YR 2.5/2) masses of iron-manganese accumulation with diffuse boundaries and strong brown (7.5YR 5/6) surfaces throughout; 17 percent exchangeable sodium; slightly acid; gradual smooth boundary.
Btng1--27 to 35 inches; light brownish gray (10YR 6/2) silty clay loam; weak coarse prismatic structure; firm; few very fine roots; common fine vesicular pores; few distinct gray (10YR 5/1) clay films on vertical faces of peds and few distinct black (10YR 2/1) and very dark gray (10YR 3/1) organo-clay films lining root channels and pores; few medium faint dark gray (10YR 4/1) iron depletions and few medium distinct dark yellowish brown (10YR 4/4) and light yellowish brown (10YR 6/4) masses of iron accumulation in the matrix; common coarse irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation with diffuse strong brown (7.5YR 4/6) boundaries; 20 percent exchangeable sodium; neutral; clear smooth boundary.
Btng2--35 to 39 inches; light gray (10YR 7/1) silty clay loam; weak coarse prismatic structure; friable; few very fine roots; few very fine vesicular pores; few distinct gray (10YR 5/1) clay films on vertical faces of peds; few coarse prominent yellowish brown (10YR 5/6) masses of iron accumulation in the matrix; few medium irregular black (7.5YR 2.5/1) and common coarse irregular strong brown (7.5YR 5/6) masses of iron-manganese accumulation in the matrix; 25 percent exchangeable sodium; slightly alkaline; abrupt smooth boundary. (The combined thickness of the Bt horizons is 18 to 40 inches.)
Cng1--39 to 44 inches; light gray (10YR 7/1) silt loam; massive; friable; few very fine roots; few very fine vesicular pores; many coarse prominent yellowish brown (10YR 5/6 and 10YR 5/8), and strong brown (7.5YR 5/6) masses of iron accumulation in the matrix; common medium and coarse irregular black (7.5YR 2.5/1) and strong brown (7.5YR 5/6) masses of iron-manganese accumulation; few medium irregular white (10YR 8/1) carbonate nodules throughout; 25 percent exchangeable sodium; slightly effervescent; slightly alkaline; abrupt smooth boundary.
Cng2--44 to 62 inches; light gray (10YR 7/1) silt loam; massive; friable; few fine tubular and vesicular pores; few distinct very dark grayish brown (10YR 3/2) clay films lining root channels and pores; many coarse prominent yellowish brown (10YR 5/6 and 10YR 5/8) masses of iron accumulation in the matrix; few medium irregular black (7.5YR 2.5/1) medium and coarse irregular strong brown (7.5YR 5/6) masses of iron-manganese accumulation; about 25 percent exchangeable sodium; slightly effervescent; moderately alkaline; gradual smooth boundary.
Cg--62 to 80 inches; light gray (10YR 7/1) silt loam; massive; friable; few distinct very dark grayish brown (10YR 3/2) organo-clay films lining root channels; many coarse prominent yellowish brown (10YR 5/6) masses of iron accumulation in the matrix; few fine irregular black (7.5YR 2.5/1) and common medium irregular strong brown (7.5YR 5/6) masses of iron-manganese accumulation; moderately alkaline.
TYPE LOCATION: St. Clair County, Illinois; about 2 miles south of Smithton; 1,202 feet west and 84 feet south of the northeast corner of section 9, T. 2 S., R. 8 W.; USGS Freeburg, IL topographic quadrangle; lat. 38 degrees, 22 minutes, 52 seconds North and long. 89 degrees, 59 minutes, 7 seconds West. NAD 27.
RANGE IN CHARACTERISTICS: The depth to the base of the natric horizon is typically 35 to 50 inches and ranges from 30 to 60 inches. Loess thickness typically is greater than 60 inches, but in some pedons, is as thin as 45 inches. The particle-size control section averages between 27 and 35 percent clay and less than 10 percent sand. The maximum clay content in any subhorizon is 42 percent. Carbonates commonly are in the natric horizon, but are not everywhere present.
The Ap horizon has hue of 10YR, value of 3 to 5 (5 or 6 dry), and chroma of 2 or 3. Clay content averages 18 to 27 percent and ranges from 12 to 35 percent. Sand content is less than 7 percent. Reaction is strongly acid to neutral. Severely eroded pedons have textures of silt loam or silty clay loam, and range in reaction from very strongly acid to neutral.
The E horizon has hue of 10YR, value of 5 or 6, and chroma of 2. Clay content ranges from 12 to 27 percent and sand content is less than 7 percent. Reaction is strongly acid to neutral. In some eroded areas the E horizon has been mixed with the Ap horizon.
The Btn and Btng horizon has hue of 10YR or 2.5Y; value of 4 to 7; and chroma of 1 to 6. It typically has chroma of 3 or higher in the upper part and becomes gleyed in the lower part. Redox features have hue of 10YR, 7.5YR, or 5YR; value of 2.5 to 6; and chroma of 1 to 8. Clay depletions, where present, have a hue of 10YR, value of 6 to 8, and chroma of 1 or 2. The Bt horizon is dominantly silty clay loam but may have thin subhorizons of silty clay and grades to silt loam in the lower part in some pedons. Clay content averages 27 to 35 percent in the upper part and averages 20 to 35 percent in the lower part. Some pedons have thin subhorizons that range to 42 percent clay. Sand content is less than 7 percent. Reaction is very strongly acid to slightly alkaline in the upper part, and is neutral to strongly alkaline in the lower part. The exchangeable sodium percentage is less than 15 percent throughout the upper 6 inches of the natric horizon or in all horizons within 16 inches of the soil surface, whichever is deeper.
Some pedons have a Bg, BC, 2Bt, 2Bg, or 2BC horizon in the lower part of the solum.
The Cng and/or Cg horizons have hue of 10YR, 2.5Y, or 5Y; value of 5 to 7; and chroma of 1 or 2. It is silt loam, loam, or silty clay loam. Reaction is slightly alkaline to strongly alkaline. Some pedons contain carbonates. Clay content is 15 to 30 percent and sand content is less than 7 percent.
Some pedons have a 2Cg, or buried horizons of older soils below a depth of 45 inches. These horizons typically are silt loam, loam, silty clay loam, or clay loam.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Darmstadt soils are on nearly level interfluves, convex summits, and in upland drainageways on till plains. Slope ranges from 0 to 10 percent. These soils contain a concentration of exchangeable sodium in the subsoil. These soils typically formed in loess, or in loess and the underlying silty pedisediment. The material beneath the loess is Illinoisan till or the silty erosional sediments that lie above the till and contains a component of sand. The loess is late Wisconsinan Peoria Silt and the underlying silty material is early Wisconsinan Roxana Silt. The till commonly contains a strongly developed paleosol. Mean annual temperature is 53 to 57 degrees F., mean annual precipitation is 36 to 42 inches, frost-free period is 175 to 200 days, and elevation is 400 to 750 feet above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cisne, Cowden, Coulterville, Grantfork, Herrick, Hoyleton, Huey, Oconee, Piasa, and Tamalco soils. The poorly drained Cisne, Cowden, Huey, and Piasa soils are on broad, nearly level interfluves. Cisne and Cowden soils are in fine-textured families and do not have a natric horizon. The somewhat poorly drained Coulterville soils contain a concentration of exchangeable sodium in the subsoil, but do not have a natric horizon, and they are on similar landforms nearby. The somewhat poorly drained Grantfork soils contain a concentration of exchangeable sodium in the subsoil, and are on side slopes below the Darmstadt soils. The somewhat poorly drained Herrick, Hoyleton, and Oconee soils are in fine-textured families and do not have a natric horizon. Hoyleton and Oconee soils are in a complex pattern with Darmstadt soils on the landscape in most places. The moderately well drained Tamalco soils are in a fine-textured family, have a natric horizon, and are on positions slightly higher on the landform.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained. Permeability is very slow. The potential for surface runoff is negligible to very high. In drained areas, depth to the top of an intermittent perched high water table is 0.5 foot to 2.0 feet from December to April in normal years.
USE AND VEGETATION: Most areas of Darmstadt soils are used for cultivated crops such as corn, small grains, and soybeans. Native vegetation is mixed hardwood forest or prairie grasses.
DISTRIBUTION AND EXTENT: Southern Illinois. The extent is moderate, mainly in MLRA(s) 113 and 114.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: St. Clair County, Illinois, 1975.
REMARKS: This update (11/2004) changes the classification from Albic Natraqualfs to Aquic Natrudalfs.
Diagnostic horizons and features in this pedon include:
..Ochric epipedon - from the surface of the soil to a depth of 11 inches (Ap and E horizons);
..Albic horizon - from a depth of 8 to 11 inches (E horizon);
..Natric horizon - from a depth of approximately 11 to 39 inches (Btn1, Btn2, Btn3, Btng1, and Btng2 horizons);
..Aquic conditions - periodic saturation and reduction indicated by redoximorphic features throughout the soil;