LOCATION CALCOUSTA IA+MN

Established Series
Rev. RDF-JAM-TWN
01/2011

CALCOUSTA SERIES

The Calcousta series consists of very deep, very poorly drained soils formed in silty lacustrine sediments more than 1 meter thick in lake basins on till plains. Slope ranges from 0 to 1 percent. Mean annual air temperature is about 8 degrees C. Mean annual precipitation is about 740 millimeters.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, calcareous, mesic Typic Endoaquolls

TYPICAL PEDON: Calcousta silty clay loam, on a slope of less than 1 percent, on a lake plain, in a cultivated field. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 23 centimeters; black (N 2/0) silty clay loam, very dark gray (N 3/0) dry; weak medium subangular blocky structure; friable; few small snail shell fragments; strongly effervescent; moderately alkaline; abrupt smooth boundary.

A--23 to 38 centimeters; black (10YR 2/1) silty clay loam, dark gray (10YR 4/1) dry; weak medium subangular blocky structure; friable; krotovina mixing of olive gray (5Y 4/2) in the lower part; some dark gray (5Y 4/1) clay depletions in root channels; slightly effervescent; slightly alkaline; abrupt smooth boundary. (Combined thickness of the A horizon is 20 to 46 centimeters.)

Bg--38 to 53 centimeters; olive gray (5Y 4/2) silty clay loam; weak fine subangular blocky structure; friable; very dark gray (5Y 3/1) organic coats on faces of peds; common fine faint olive (5Y 5/4) redoximorphic concentrations; strongly effervescent; moderately alkaline; clear smooth boundary. (5 to 15 centimeters thick)

Cg--53 to 152 centimeters; olive gray (5Y 5/2) and light olive gray (5Y 6/2) silty clay loam; massive; friable; few white (5Y 8/1) lime concretions; common fine prominent yellowish red (5YR 4/6) and common medium prominent strong brown (7.5YR 5/8) redoximorphic concentrations; strongly effervescent; moderately alkaline.

TYPE LOCATION: Major Land Resource Are (MLRA) 103-Central Iowa and Minnesota Till Prairies, Pocahontas County, Iowa subset; about 3 1/2 miles south of Rolfe; located about 1,860 feet north and 290 feet west of the southeast corner of section 29, T. 92 N., R. 31 W; USGS Rolfe topographic quadrangle; lat 42 degrees 45 minutes 09 seconds N. and long 94 degrees 31 minutes 21 seconds W; NAD83.

RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon--20 to 46 centimeters
Depth to carbonates--at the surface and throughout the profile
Content of clay in the particle-size control section (weighted average)--24 to 35 percent
Content of sand in the particle-size control section (weighted average)--less than 15 percent
Calcium carbonate equivalent--5 to 20 percent

Ap or A horizons:
Hue--10YR, 2.5Y or is neutral
Value--2
Chroma--0 or 1
Texture--silty clay loam, silt loam, or mucky silt loam
Clay content--24 to 35 percent
Sand content--less than 15 percent
Reaction--slightly alkaline or moderately alkaline

Bg horizon:
Hue--5Y
Value--4 to 6
Chroma--1 or 2
Texture--silty clay loam or silt loam
Clay content--24 to 35 percent
Sand content--less than 15 percent
Reaction--slightly alkaline or moderately alkaline

Cg horizon:
Hue--5Y
Value--5 or 6
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--22 to 30 percent
Sand content--10 to 20 percent
Reaction--slightly alkaline or moderately alkaline

Some pedons have Cg horizons that have stratified materials with textures of loam, very fine sandy loam or clay loam

COMPETING SERIES: These are the Prinsburg and Spicer series.
Prinsburg--have a sand content of 20 to 40 percent in the lower third of the series control section
Spicer--presently there is an overlap with the Calcousta series and there is no clear differentiation

GEOGRAPHIC SETTING:
Parent material--lacustrine sediments more than 1 meter thick
Landform--lake basins on till plains, Late Wisconsin age
Slope--0 to 1 percent
Elevation--300 to 400 meters above sea level
Mean annual air temperature--6 to 10 degrees C
Mean annual precipitation--585 to 890 millimeters
Frost-free period--155 to 200 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Canisteo, Harps, and Wacousta soils.
Canisteo--are at slightly higher landscape positions on plane slopes or on rims of depressions and have a sand content that averages more than 20 percent in the particle-size control section
Harps--are at slightly higher landscape positions on plane slopes or on rims of depressions and have a sand content that averages more than 20 percent in the particle-size control section
Wacousta--are on landscape positions similar to the Calcousta soils and do not have carbonates within a depth of 30 centimeters

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--very poorly drained--these soils are frequently saturated at the surface of the soil during wettest periods of normal years
Saturated hydraulic conductivity--1.00 to 10.00 micrometers per second
Surface runoff potential--negligible
Ponding--common in undrained areas

USE AND VEGETATION:
Where drained, these soils are cultivated. The principal crops are corn and soybeans with some oats and legume hays. The natural vegetation is grasses and sedges tolerant of wetness.

DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic section--Western lake section
MLRA--Central Iowa and Minnesota Till Prairies (103)
LRR M; central and north-central Iowa and south-central Minnesota
Extent--small

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota

SERIES ESTABLISHED: Pocahontas County, Iowa, 1982.

REMARKS:
Particle-size control section--the zone from a depth of 25 to 100 centimeters
series control section--the zone from the surface to a depth of 150 centimeters.

Diagnostic horizons and features recognized in this pedon include:
mollic epipedon--the zone from the surface of the soil to a depth of 38 centimeters (Ap and A horizons);
cambic horizon--the zone from a depth of 38 to 53 centimeters (Bg horizon);
aquic moisture regime. 1/31/2011-TYPE LOCATION error was corrected.

These soils were formerly included with Wacousta soils and were correlated as Wacousta Variant in Calhoun County, Iowa.

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

Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.

National Cooperative Soil Survey
U.S.A.