LOCATION COLO                    IA+IL KS MN MO NE SD

Established Series
Rev. ROD-LDC
09/2016

COLO SERIES

The Colo series consists of very deep, poorly drained soils formed in alluvium. These soils are on floodplains, low stream terraces, alluvial fans, and upland drainageways. Slope ranges from 0 to 5 percent. Mean annual air temperature is about 10 degrees C. Mean annual precipitation is about 775 millimeters.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Cumulic Endoaquolls

TYPICAL PEDON: Colo silty clay loam, on a slope of less than 1 percent, in a cultivated field, at an elevation of about 275 meters above sea level. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 20 centimeters; black (N 2.5/) silty clay loam, black (10YR 2/1) dry; weak fine subangular blocky structure parting to weak fine granular; friable; moderately acid; abrupt smooth boundary.

A1--20 to 36 centimeters; black (N 2.5/) silty clay loam, black (10YR 2/1) dry; weak fine subangular blocky structure parting to moderate fine granular; friable; moderately acid; diffuse smooth boundary.

A2--36 to 58 centimeters; black (N 2.5/) silty clay loam, very dark gray (10YR 3/1) dry; weak medium subangular blocky structure parting to weak fine granular; friable; slightly acid; gradual smooth boundary.

A3--58 to 86 centimeters; black (10YR 2/1) silty clay loam, very dark gray (10YR 3/1) dry; weak medium subangular blocky structure; friable; slightly acid; gradual smooth boundary. (Combined thickness of the A horizon is 75 to 102 centimeters.)

BA--86 to 102 centimeters; very dark gray (10YR 3/1) silty clay loam, dark gray (10YR 4/1) dry; weak medium subangular blocky structure; friable; slightly acid; gradual smooth boundary. (0 to 25 centimeters thick)

Bg--102 to 117 centimeters; very dark gray (10YR 3/1) silty clay loam, dark gray (10YR 4/1) and gray (10YR 5/1) dry; weak medium prismatic structure parting to weak medium subangular blocky; friable; slightly acid; gradual smooth boundary. (0 to 80 centimeters thick)

BCg--117 to 132 centimeters; dark gray (10YR 4/1) silty clay loam; weak coarse prismatic structure parting to weak medium subangular blocky; friable; slightly acid; gradual smooth boundary. (0 to 25 centimeters thick)

Cg--132 to 152 centimeters; dark gray (10YR 4/1) silt loam; massive; friable; few fine prominent brown (7.5YR 5/4) redoximorphic concentrations; slightly acid.

TYPE LOCATION: Major Land Resource Area (MLRA) 104-Eastern Iowa and Minnesota Till Prairies, Tama County, Iowa subset; about 3 1/2 miles west of Traer; located about 350 feet west and 1,800 feet north of the southeast corner of section 12, T. 85 N., R. 15 W.; USGS Gladbrook NE topographic quadrangle; lat. 42 degrees 11 minutes 11 seconds N. and long. 92 degrees 32 minutes 3 seconds W., NAD 83.

RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon--more than 90 centimeters
Depth to carbonates--more than 150 centimeters
Clay content in the particle-size control section (weighted average)--27 to 35 percent
Sand content in the particle-size control section (weighted average)--less than 15 percent fine sand and sand coarser than fine sand

Ap or A horizon:
Hue--10YR to 5Y, or is neutral
Value--2, 2.5, or 3
Chroma--0 to 2
Texture--silty clay loam or silt loam
Clay content--24 to 35 percent
Sand content--1 to 20 percent
Reaction--moderately acid to neutral (5.6 to 7.3)

Overwash phase:
Thickness--15 to 46 centimeters
Hue--10YR
Value--3 to 5
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--20 to 30 percent
Reaction--slightly acid to moderately alkaline (6.1 to 8.4)

Some pedons have an AC horizon

BA horizon:
Hue--10YR to 5Y
Value--2, 2.5, or 3
Chroma--1 or 2
Texture--silty clay loam
Clay content--30 to 35 percent
Sand content--less than 15 percent
Reaction--moderately acid to neutral (5.6 to 7.3)

Bg horizon:
Hue--10YR or 5Y
Value--2 to 4
Chroma--1
Texture--silty clay loam
Clay content--30 to 35 percent
Sand content--less than 15 percent
Reaction--moderately acid to neutral (5.6 to 7.3)

BCg horizon:
Hue--10YR to 5Y
Value--3 to 6
Chroma--1 or 2
Texture--silty clay loam
Clay content--30 to 35 percent
Sand content--less than 15 percent
Reaction--moderately acid to neutral (5.6 to 7.3)

Cg horizon:
Hue--10YR to 5Y
Value--3 to 6
Chroma--1 or 2
Texture--silty clay loam, silt loam, or clay loam
Clay content--25 to 35 percent
Sand content--1 to 30 percent
Reaction--moderately acid to neutral (5.6 to 7.3)

Some pedons have sandy or gravelly sediments below a depth of 150 centimeters

COMPETING SERIES: These are the Afton, Catherine, Clementine, Humansville, Otter, Pastolla, Sawmill, and Whitewood series.
Afton--have a mollic epipedon 61 to 81 centimeters thick
Catherine--are in areas that have a mean annual precipitation of less than 640 millimeters
Clementine--are in areas that have a mean annual precipitation of less than 64 millimeters and have carbonates within a depth of 102 centimeters
Humansville--have a mollic epipedon 61 to 91 centimeters thick and are in areas that have a mean annual precipitation range of 960 to 1140 millimeters
Otter--have a clay content of 18 to 27 percent in the particle-size control section
Pastolla--are in areas that have a mean annual precipitation range of 300 to 520 millimeters
Sawmill--have a mollic epipedon 61 to 91 centimeters thick
Whitewood--have carbonates within a depth of 132 centimeters

GEOGRAPHIC SETTING:
Parent material--alluvium
Landform--floodplains, low stream terraces, alluvial fans, and upland drainageways
Slope--0 to 5 percent
Elevation--150 to 450 meters above sea level
Mean annual air temperature--8 to 12 degrees C
Mean annual precipitation--600 to 950 millimeters
Frost-free period--145 to 175 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bremer, Ely, Nevin, Nodaway, and Wiota soils.
Bremer--are at the slightly higher elevations and have a mollic epipedon that ranges from 61 to 91 centimeters thick
Ely--are at the slightly higher elevations on low foot slopes and alluvial fans and have a frequently saturated zone within a depth of 0.3 meter during the wettest periods of normal years
Nevin--are at the higher elevations and have a frequently saturated zone within a depth of 0.3 meter during the wettest periods of normal years
Nodaway--are at slightly higher elevations and do not have a mollic epipedon
Wiota--are at the higher elevations on stream terraces and have a mollic epipedon that ranges from 50 to 81 centimeters thick

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--poorly drained--these soils are frequently saturated at the soil surface during the wettest portions of normal years and is considered apparent
Saturated hydraulic conductivity--1.00 to 10.00 micrometers per second (moderately high)
Surface runoff potential--negligible to low
Flooding--rarely flooded to frequently flooded for very brief to long periods during the months of February to November from precipitation events and snowmelt

USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, and hay. A few areas are in permanent pasture. The native vegetation is big bluestem, indiangrass, switchgrass, and other grasses of the tall grass prairie. See Additional Data section for native vegetative cover in Iowa and Minnesota.

DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Western lake section, Wisconsin driftless section, Till plains, and Dissected till plains
MLRAs--Wisconsin and Minnesota Sandy Outwash (91),
Rolling Till Prairie (102A),
Central Iowa and Minnesota Till Prairies (103),
Eastern Iowa and Minnesota Till Prairies (104),
Northern Mississippi Valley Loess Hills (105),
Iowa and Missouri Deep Loess Hills (107),
Illinois and Iowa Deep Loess and Drift (108),
Iowa and Missouri Heavy Till Plain (109),
Northern Illinois and Indiana Heavy Till Plain (110),
Central Claypan Areas (113),
Southern Illinois and Indiana Thin Loess and Till Plain (114), and
Central Mississippi Valley Wooded Slopes (115)
LRR M; Iowa, southern Minnesota, Nebraska, Missouri, Kansas, and Illinois
Extent--large

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

SERIES ESTABLISHED: Monona County, Iowa, 1956.

REMARKS:
Particle-size control section--the zone from a depth of 25 to 100 centimeters (A1, A2, and BA horizons);
series control section--the zone from the surface to a depth of 150 centimeters (Ap, A1, A2, A3, BA, Bg, BCg and Cg horizons).

Diagnostic horizons and features recognized in this pedon include:
mollic epipedon--the zone from the surface to a depth of 117 centimeters (Ap, A1, A2, A3, BA, and Bg horizons);
cambic horizon--the zone from a depth of 117 to 132 centimeters (BCg horizon);
aquic moisture regime.

Cation-exchange class is inferred from lab data for similar soils in the surrounding area.

Taxonomy version--Keys to Soil Taxonomy, twelfth edition, 2014.

ADDITIONAL DATA:
Complete physical and chemical data on Colo soils is available in Dr. M. E. Collins' Ph.D. dissertation, Iowa State University Library, Ames, Iowa. Forty-seven profiles from Iowa, Illinois, Missouri, and Nebraska were sampled and described. This pedon from Tama County is identified in the study as Soil 86.

In Iowa and Minnesota, the native vegetative cover is a herbaceous wetland community commonly inhabited with Bluejoint Grasses, Fowl Bluegrasses, Green Muhlies, Fox Sedges, Field Sedges, Dudleys Rushes, Torreys Rushes, Swamp Milkweeds, False Sneezeweeds, False Asters, New England Asters, White Panicled Asters, and Wild Mints. Source: Iowa State Office, Natural Resources Conservation Service, Des Moines, IA.

OSD Typical Pedon: Pedon number 2006IA171999.

---

National Cooperative Soil Survey
U.S.A.