LOCATION CAIRO IL+MO

Established Series
Rev. JBF-WDP-JWS-DRW
03/2011

CAIRO SERIES

The Cairo series consists of deep, poorly drained soils on low terraces and high bottomlands of broad flood plains. They formed in 20 to 39 inches of clayey slackwater sediments and are underlain by sandy alluvium. Slopes range from 0 to 4 percent. Mean annual precipitation is about 1143 millimeters (45 inches), and mean annual temperature is about 15 degrees C (59 degrees F).

TAXONOMIC CLASS: Clayey over sandy or sandy-skeletal, smectitic over mixed, thermic Vertic Endoaquolls

TYPICAL PEDON: Cairo silty clay - near the crest of a low terrace ridge in a cultivated field at an elevation of about 101 meters (333 feet) above mean sea level. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 15 centimeters (0 to 6 inches); black (10YR 2/1) silty clay, very dark gray (10YR 3/1) dry; weak fine angular blocky structure; very firm; neutral; clear smooth boundary.

A--15 to 43 centimeters (6 to 17 inches); very dark gray (10YR 3/1) silty clay, dark gray (10YR 4/1) dry; moderate coarse prismatic structure parting to strong medium angular blocky; very firm; many distinct very dark brown (10YR 2/2) organic coatings on faces of peds; common fine prominent yellowish brown (10YR 5/6) and common medium prominent strong brown (7.5YR 5/6) masses of oxidized iron and common medium faint black (10YR 2/1) manganese masses; neutral; clear smooth boundary. (Combined thickness of the A horizon is 10 to 20 inches.)

Bg1--43 to 76 centimeters (17 to 30 inches); dark gray (10YR 4/1) silty clay; weak medium prismatic structure parting to moderate medium angular blocky; very firm; many distinct very dark grayish brown (10YR 3/2) organic coatings on faces of peds; few fine prominent yellowish brown (10YR 5/6) and yellowish red (5YR 5/8) masses of oxidized iron; neutral; clear smooth boundary. (8 to 20 inches thick)

2Bg2--76 to 81 centimeters (30 to 32 inches); dark gray (10YR 4/1) sandy loam; weak medium angular blocky structure; firm; few small pockets of yellowish brown (10YR 5/6) loamy fine sand; many fine prominent strong brown (7.5YR 5/6) and yellowish red (5YR 5/8) masses of oxidized iron; slightly acid; clear smooth boundary. (0 to 5 inches thick)

2C1--81 to 89 centimeters (32 to 35 inches); mottled yellowish brown (10YR 5/4), strong brown (7.5YR 5/6) and yellowish red (5YR 5/8) loamy fine sand; single grain; loose; slightly acid; gradual smooth boundary.

2C2--89 to 203 centimeters (35 to 80 inches); mottled yellowish brown (10YR 5/4) and pale brown (10YR 6/3) loamy fine sand; single grain; loose; thin horizontal bands of strong brown (7.5YR 5/8); slightly acid.

TYPE LOCATION: Alexander County, Illinois; about 2 miles southeast of East Cape Girardeau; 1,365 feet north and 620 feet west of the southeast corner of sec. 18, T. 14 S., R. 3 W.; USGS McClure, IL - MO topographic quadrangle; lat. 37 degrees 17 minutes 46 seconds N. and long. 89 degrees 28 minutes 24 seconds W.; UTM Easting: 280772, Northing: 4130579, NAD 83.

RANGE IN CHARACTERISTICS:
Thickness of solum and the depth to the sandy 2C horizon: 20 to 39 inches
Thickness of the mollic epipedon: 10 to 20 inches thick and extends into the B horizon in some pedons
Depth to strongly contrasting particle size classes in the control section: 20 to 39 inches
Particle-size control section: averages more than 40 percent clay in the A and Bg1 horizons; the 2C horizons averages less than 20 percent clay.
Reaction: slightly acid to slightly alkaline
Depth to carbonates: typically greater than 60 inches

Ap or A horizon
Hue: 10YR or neutral
Value: 2 or 3 (3 to 5 dry)
Chroma: 0 to 2
Redoximorphic features are present in the A horizon
Fine-earth texture: silty clay or clay

Bg horizon
Hue: 10YR, 2.5Y, 5Y or neutral
Value: 3 to 5 (5 to 7 dry)
Chroma: 0 or 1
Redoximorphic features are present
Fine-earth texture: silty clay or clay

2Bg horizon
Hue: 10YR, 2.5Y, 5Y or neutral
Value: 3 to 6
Chroma: 0 to 2
Redoximorphic features are present
Fine-earth texture: silty clay loam, clay loam, sandy clay loam, sandy loam or loam

2C horizons
Hue: 10YR or 7.5YR; less commonly 5YR, 2.5Y or neutral
Value: 4 or 5
Chroma: 0 to 6
Redoximorphic features are present
Fine-earth texture: dominantly loamy fine sand, loamy sand, or fine sand, but some pedons contain thin discontinuous bands of sandy loam, loam, silt loam, or silty clay loam

COMPETING SERIES: This is the only series in this family. Other series in closely related families are Darwin, Fults, Griffith and Osage soils. The Darwin, Fults, Griffith, and Osage soils lack contrasting textures within a depth of 40 inches. In addition Darwin and Fults soils are mesic.

GEOGRAPHIC SETTING: Cairo soils are on broad flood plains. Typically they are on low terraces and high flood plains. A wet phase has been recognized. Slope gradients range from 0 to 4 percent. These soils formed in 51 to 99 centimeters (20 to 39 inches) of slackwater sediments and are underlain by sandy alluvium. Mean annual temperature ranges from 12 to 17 degrees C. (54 to 64 degrees F)., mean annual precipitation ranges from 1016 to 1270 millimeters (40 to 50 inches), frost free period ranges from 190 to 220 days, and elevation ranges from 85 to 152 meters (280 to 500 feet) above mean sea level.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bowdre, Cooter, Darwin, and Riley soils. Bowdre and Cooter soils have sand at less than 20 and 24 inches respectively. Darwin soils typically are lower lying on the topography. Riley soils are fine-loamy over sandy or sandy-skeletal. Bowdre and Riley soils are on similar low terraces as the Cairo soils. Cooter soils are both on low ridges and in old channels and bayous.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Poorly drained. The potential for surface runoff is low. Saturated hydraulic conductivity is low or moderately low (0.07 to 0.42 micrometers/sec) in the clayey sediments and high or very high 42.34 to 141.14 micrometers/sec) in the underlying sandy alluvium.Permeability is very slow in the clayey sediments and rapid in the underlying sandy alluvium.

USE AND VEGETATION: Most areas are used for cultivated crops. Corn and soybeans are the common crops. Areas too wet to cultivate are used for pasture or are in bottomland hardwoods.

DISTRIBUTION AND EXTENT: Southern Illinois and southern Missouri along the flood plain of the Mississippi River. The extent is moderate. The type location is in MLRA 115B and the series extent includes MLRA 131.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana

SERIES ESTABLISHED: Alexander County, Illinois, 1968.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 43 centimeters (17 inches), (Ap and A horizons)
Cambic horizon - 25 to 114 centimeters (10 to 45 inches), (Bg1 and 2Bg2 horizons)
Redoximorphic features in the mollic epipedon and throughout the pedon.
Aquic conditions inferred from dominant chroma of 1 in all layers below the surface layer and above the sandy 2C horizon
Aquic moisture regime and endosaturation are inferred based on the position on the landform
Strongly contrasting particle-size class within the control section

Cairo soils were previously classified as:
1. Vertic Haplaquolls, clayey over sandy or sandy-skeletal, smectitic, thermic, changed 7/94.
2. Vertic Haplaquolls, clayey over sandy or sandy-skeletal, montmorillonitic, thermic, changed 5/76.
3. Typic Haplaquolls, clayey over sandy or sandy-skeletal, montmorillonitic, thermic, 1968.
4. Low Humic Gley soil in the 1938 classification by great group system.

National Cooperative Soil Survey
U.S.A.