LOCATION ST. CHARLES IL+IN WIEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Hapludalfs
TYPICAL PEDON: St. Charles silt loam - on an north-facing slope of 3 percent in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 cm (0 to 8 inches); brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; moderate medium granular structure; friable; few fine roots; moderately acid; abrupt smooth boundary. [8 to 25 cm (3 to 10 inches) thick]
Bt1--20 to 38 cm (8 to 15 inches); yellowish brown (10YR 5/4) silty clay loam; moderate fine subangular blocky structure; friable; few fine roots; many faint dark brown (10YR 3/3) organic coatings and dark yellowish brown (10YR 4/4) clay films on faces of peds; moderately acid; clear smooth boundary.
Bt2--38 to 53 cm (15 to 21 inches); yellowish brown (10YR 5/4) silty clay loam; moderate medium subangular blocky structure; friable; few fine roots; many faint dark yellowish brown (10YR 4/4) clay films on faces of peds; moderately acid; clear smooth boundary.
Bt3--53 to 86 cm (21 to 34 inches); yellowish brown (10YR 5/4) silty clay loam; weak medium prismatic structure parting to moderate medium subangular blocky; friable; few fine roots; many faint dark yellowish brown (10YR 4/4) clay films on faces of peds; few fine rounded dark extremely weakly cemented iron-manganese accumulations throughout; moderately acid; clear smooth boundary.
Bt4--86 to 112 cm (34 to 44 inches); yellowish brown (10YR 5/4) silt loam; moderate medium prismatic structure parting to moderate medium subangular blocky; friable; many faint dark yellowish brown (10YR 4/4) clay films and many distinct light gray (10YR 7/2) (dry) silt coatings on faces of peds; common medium distinct brown (7.5YR 4/4) extremely weakly cemented iron-manganese accumulations in the matrix; moderately acid; clear smooth boundary.
Bt5--112 to 127 cm (44 to 50 inches); yellowish brown (10YR 5/4) silt loam; moderate medium subangular blocky structure; friable; many distinct dark yellowish brown (10YR 4/4) clay films and light gray (10YR 7/2) (dry) silt coatings on faces of peds; few fine distinct strong brown (7.5YR 5/6) masses of oxidized iron in the matrix; moderately acid; clear smooth boundary. [Combined thickness of the Bt horizons is 51 to 114 cm (20 to 45 inches).]
2Bt6--127 to 145 cm (50 to 57 inches); yellowish brown (10YR 5/6) stratified loam, sandy loam, and silt loam; weak medium subangular blocky structure; friable; common distinct dark yellowish brown (10YR 4/4) clay films on faces of peds; moderately acid; clear smooth boundary. [10 to 25 cm (4 to 10 inches) thick]
2C--145 to 152 cm (57 to 60 inches); yellowish brown (10YR 5/4) stratified loam and silt loam; massive; friable; moderately acid.
TYPE LOCATION: Bureau County, Illinois; about 2 miles south and 2 1/2 miles east of Wyanet; 80 feet north and 2,170 feet west of the southeast corner of sec. 26, T. 16 N., R. 8 E.; USGS, Wyanet, Illinois, topographic quadrangle: lat. 41 degrees 20 minutes 9 seconds N., and long. 89 degress 32 minutes 12 seconds W., NAD 27; UTM Zone 16T, 0287740 easting, 4579143 northing, NAD 83:
RANGE IN CHARACTERISTICS: The depth to the base of soil development is 112 to 178 cm (44 to 70 inches). The depth to free carbonates is greater than 112 cm (44 inches). The depth to the base of the argillic horizon is greater than 89 cm (35 inches). The depth to horizons with more than 10 percent sand is 102 to 152 cm (40 to 60 inches). The particle-size control section averages between 27 to 35 percent clay and less than 10 percent fine sand or coarser. The dominant clay mineral in the upper silty layers is smectite and in the lower loamy layers is illite.
The upper part of the control section (Ap, A, E) has properties as follows. The Ap or A horizon has value of 3 to 5 and chroma of 1 to 3. It is silt loam except plow layers that contain subsoil material may be silty clay loam. The E horizon, where present, has value of 4 to 6 and chroma typically of 3 and less commonly of 2 or 4.The E horizon is incorporated into the Ap horizon in most cultivated pedons. Clay content ranges from 20 to 35 percent. Reaction is strongly acid to slightly alkaline.
The second part of the control section (BE, Bt) has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 3 to 6. It dominantly is silty clay loam, but some subhorizons are silt loam. Clay content ranges from 24 to 35 percent. Reaction is moderately acid or strongly acid in at least one subhorizon, and ranges from very strongly acid to neutral.
The third part of the control section (2Bt, 2BC) has hue of 10YR or 7.5YR, value of 4 to 6, and chroma of 3 to 6. It commonly is stratified; textures include loam, sandy loam, fine sandy loam, sandy clay loam, clay loam, or silt loam. Clay content ranges from 15 to 30 percent and sand content ranges from 20 to 55 percent with some subhorizons having up to 60 percent sand and up to 15 percent gravel. Reaction is strongly acid to neutral. Some pedons have a 2BC horizon.
The lower part of the control section (2C) has colors in the same range as the 2Bt or 2BC horizon. It commonly is silt loam, loam, sandy loam, gravelly loam, or gravelly sandy loam, and is often stratified. Clay content ranges from 10 to 25 percent and sand content ranges from 20 to 60 percent. The content of fine sand plus very fine sand is less than 50 percent of total sand content. Some subhorizons have up to 95 percent sand or up to 80 percent gravel. Volume of rock fragments is less than 20 percent. Some pedons have subhorizons that are loamy sand and a sandy substratum phase is recognized. Some pedons are sand and gravel in the 2C horizon and a gravelly substratum phase is recognized. Reaction is moderately acid to moderately alkaline.
COMPETING SERIES: These are the Baraboo, Bertrand, Blackhammer, Cadiz, Camden, Dodge, Dubuque, Fayette, Flagg, Hackers, Jackson, Jemerson, Knowles, La Farge, Lomira, Marseilles, Martinsburg, Menfro, Minnith, Navlys, Palermo, Palsgrove, Pepin, Piscasaw, Ridgway, Rozetta, Ruma, Rush, Sandview, Seaton, Stookey, Sylvan, Uniontown, Weingarten, Westbend, Westmore, and Yellowriver series. Baraboo, Dubuque, Knowles, La Farge and Marseilles soils are moderately deep to a lithic or paralithic contact. Bertrand, Jackson, Jemerson, Pepin, Seaton and Stookey soils average less than 27 percent clay in the particle-size control section. Blackhammer soils have rock fragments in the lower part of the series control section that are dominantly chert and sandstone. Cadiz soils have more than 25 percent clay in the lower part of the series control section. Camden, Minnith, Piscasaw, Ridgway and Yellowriver soils have horizons with more than 10 percent sand above a depth of 102 cm (40 inches). Dodge, Lomira, Navlys, and Sylvan soils contain carbonates above a depth of 102 cm (40 inches). Fayette, Menfro, Palermo, Rozetta, Ruma and Stookey soils have less than 10 percent sand throughout the series control section. Flagg soils have at least one subhorizon of the 2Bt horizon that has hue of 5YR or redder on faces of peds or in the matrix. Hackers soils have hues of 2.5YR or 5YR dominant in the solum and throughout the substratum. Martinsburg soils have E horizons that are at least 31 cm (12 inches) thick and have the layer of maximum clay content at a depth of 76 to 91 cm (30 to 36 inches). Palsgrove soils formed in loess and residuum weathered from limestone and have a lithic contact at depths of 102 to 152 cm (40 to 60 inches). Rush soils have less than 10 percent clay and average more than 20 percent rock fragments in the lower part of the series control section. Sandview and Weingarten soils formed in loess or other silty material and residuum weathered from limestone and have more than 27 percent clay in the lower part of the series control section. Uniontown soils have redox features in the lower part of the series control section. Westbend soils formed in residuum weathered from interbedded soft siltstone and shale bedrock and have a paralithic contact at depths of 102 to 152 cm (40 to 60 inches). Westmore soils formed in silty material and residuum weathered from interbedded siltstone, shale, sandstone, and limestone and have more than 35 percent clay in the lower part of the series control section.
GEOGRAPHIC SETTING: St. Charles soils are on summits and side slopes of loess covered outwash plains, till plains, and stream terraces. Slopes commonly are 0 to 15 percent, but some are as steep as 30 percent. St. Charles soils formed in 102 to 152 cm (40 to 60 inches) of loess and in the underlying loamy stratified outwash or sandy loam till thought to be of Wisconsin Age. The substratum commonly is stratified loamy outwash, but in some pedons is gravelly or sandy outwash or sandy loam till. Mean annual temperature ranges from 8 to 12 degrees C (46 to 54 degrees F), mean annual precipitation ranges from 762 to 1067 mm (30 to 42 inches), frost-free period ranges from 160 to 180 days, and elevation ranges from 207 to 311 meters (680 to 1020 feet) above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Batavia, Camden, Kendall, Kidder, McHenry, Sexton, Starks, and Thorp soils. Batavia soils have a dark-colored surface layer and commonly are upslope from St. Charles soils and farther from the drainageways. Camden soils are nearby on similar landscapes that have a mantle of loess 20 to 40 inches in thickness. Kendall soils are the somewhat poorly drained member of a hydro-sequence with St. Charles soils. Kidder and McHenry soils formed in sandy loam till on similar topographic positions as some St. Charles soils, but average more than 15 percent fine sand and coarser in the control section. The poorly drained Sexton and somewhat poorly drained Starks soils are on outwash plains and stream terraces nearby, and have chroma of 2 in the upper part of the sola. The nearly level, poorly drained Thorp soils have a thinner mantle of loess and are Argiaquic Argialbolls.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained. An apparent water table is at a depth of 107 to 183 cm (3.5 to 6 feet) at some time between February and June, or at depths greater than 183 cm (6 feet). The potential for surface runoff is very low on areas of less than 5 percent slopes and low on areas of 5 to 20 percent slopes. Saturated hydraulic conductivity is moderately high to high (4.23 to 14.11 micrometer per second). The areas of St. Charles series mapped as sandy and gravelly substratum phases have saturated hydraulic conductivity in the substratum as high to very high (42.34 or more micrometers per second). Permeability is moderate in the solum. The permeability is moderate in the 2C horizon of soils with loamy substratum, rapid in the 2C horizon of soils in the sandy substratum phase, and very rapid in the 2C horizon of soils in the gravelly substratum phase.
USE AND VEGETATION: Many areas are cultivated. The principal crops are corn, soybeans, small grain, and meadow. Some areas are in pasture or woodland. The soils formed under forest vegetation.
DISTRIBUTION AND EXTENT: Illinois, Indiana, and Wisconsin. The extent is large.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Kendall County, Illinois, 1941.
REMARKS: The areas of St. Charles soils mapped as sandy substratum phase and gravelly substratum phase are being evaluated during MLRA update activities to determine if new series are needed. A moderately wet phase with a 3.5 to 6.0 foot seasonal water table may also be identified in future MLRA updates.
Also, those areas of St. Charles soils that formed in loess and sandy loam till are being evaluated as part of the MLRA 95B update. A new series will be proposed for those soils.
The areas of these soils mapped in "cool mesic" and in "warm mesic" will be evaluated for possible new series.
Diagnostic horizons recognized in this pedon are: ochric epipedon - the zone from the surface to a depth of 20 cm (8 inches) (Ap horizons); argillic horizon - the zone from approximately 20 to 112 cm (8 to 44 inches) (Bt1, Bt2, and Bt3 horizons).