LOCATION KNOKE                   IA+MN

Established Series
Rev. MPK-RJK-AGG
02/2015

KNOKE SERIES

The Knoke series consists of very deep, very poorly drained soils formed in glacial sediments in depressions or in old glacial lakes. These soils have moderately slow permeability. Slopes range from 0 to 1 percent. Mean annual precipitation is about 30 inches, and mean annual air temperature is about 49 degrees F.

TAXONOMIC CLASS: Fine, smectitic, calcareous, mesic Cumulic Vertic Endoaquolls

TYPICAL PEDON: Knoke mucky silt loam - on a plane slope of less than 1 percent in a cultivated field in the bottom of a former glacial lake. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 8 inches; black (5Y 2/1) mucky silt loam, dark gray (10YR 4/1) dry; weak medium platy structure parting to weak fine subangular blocky; friable; many snail shells, violently effervescent; moderately alkaline; abrupt smooth boundary.

Al--8 to 13 inches; very dark gray (5Y 3/1) mucky silty clay loam, gray (10YR 5/1) dry; weak medium platy structure; friable; thin brown (7.5YR 5/4) coats in fine continuous vertical tubular pores, many snail shells, violently effervescent; moderately alkaline; abrupt smooth boundary.

A2--13 to 18 inches; black (5Y 2/1) mucky silty clay loam, dark gray (10YR 4/1) dry; weak medium platy structure; friable; many snail shells, thin brown (7.5YR 5/4) coats in fine continuous vertical tubular pores, violently effervescent; moderately alkaline; clear smooth boundary.

A3--18 to 33 inches; black (N 2/0) silty clay loam, dark gray (10YR 4/1) dry; weak very fine and fine subangular blocky structure; friable; few olive brown (2.5Y 4/4) dry coats in fine continuous vertical tubular pores, slightly effervescent; slightly alkaline; gradual smooth boundary.

A4--33 to 40 inches; black (N 2/0) silty clay loam, dark gray (10YR 4/1) dry; weak fine angular and subangular blocky structure; friable; few olive brown (2.5Y 4/4) dry coats in fine discontinuous vertical tubular pores; strongly effervescent; slightly alkaline; clear smooth boundary.

A5--40 to 46 inches; black (N 2/0) silty clay loam, gray (10YR 5/1) dry; weak fine prismatic structure parting to weak fine subangular blocky; friable; common medium prominent olive brown (2.5Y 4/4) Fe concentrations; strongly effervescent; slightly alkaline; clear smooth boundary. (Combined thickness of A horizons is 24 to 48 inches)

BCg--46 to 54 inches; gray (5Y 5/1), very dark gray (5Y 3/1) and dark gray (2.5Y 4/1) silty clay loam; weak fine prismatic structure; friable; strongly effervescent; moderately alkaline; gradual smooth boundary. (0 to 8 inches thick)

Cg--54 to 63 inches; gray (5Y 5/1) silty clay loam; massive; friable; common soft lime accumulations, many medium prominent dark yellowish brown (10YR 4/4) Fe concentrations;strongly effervescent; moderately alkaline.

TYPE LOCATION: Calhoun County, Iowa; about 1/2 mile west of South Twin Lake; 1,440 feet north and 50 feet west of the southeast corner of sec. 3, T. 88 N., R. 33 W.

RANGE IN CHARACTERISTICS:
Thickness of mollic epipedon: 24 to over 60 inches
Particle size control section (weighted average):
Clay content: 35 to 40 percent
Sand content: 15 to 30 percent, most of which is fine and very fine
Most pedons contain fragments of snail or clam shells.
These soils do not have stratification above depths of 4 feet.

Ap and A horizons:
Hue: 10YR, 2.5Y, 5Y, or is Neutral
Value: 2 or 3
Chroma: 0 to 2
Texture: mucky silt loam, mucky silty clay loam, or silty clay loam. Below 20 inches, the A horizon is silty clay loam, clay loam, or silty clay.
Clay content: 22 to 45 percent
Sand content: 15 to 30 percent
Reaction: slightly alkaline or moderately alkaline

Bg horizon (if present):
Hue: 10YR, 2.5Y, 5Y, or is Neutral
Value: 2 or 3
Chroma: 0 or 1
Texture: silty clay loam, clay loam, or silty clay
Clay content: 35 to 45 percent
Sand content: 15 to 30 percent
Reaction: slightly alkaline or moderately alkaline

BCg horizon:
Hue: 2.5Y, 5Y, or is Neutral
Value: 2 to 5
Chroma: 0 or 1
Texture: silty clay loam, clay loam, or silty clay
Clay content: 35 to 45 percent
Sand content: 15 to 30 percent
Reaction: slightly alkaline or moderately alkaline

Cg horizon:
Hue: 2.5Y, 5Y, or 5G
Value: 3 to 6
Chroma: 1 or 2
Texture: silty clay loam but some pedons have thin strata of loam, silt loam, or clay loam
Clay content: 20 to 35 percent
Sand content: 20 to 40 percent
Reaction: slightly alkaline or moderately alkaline

COMPETING SERIES: These are the Baltic, Delvada, Holly Springs James and Nishna soils.
Baltic soils contain accumulations of gypsum within the partilcle size control section.
Delvada soils are dry in the soil moisture control section during the growing season.
Holly Springs soils contain more than 45 percent clay in the lower one third of the series control section.
James soils contain accumulations of salts in the series control section.
Nishna soils have a sand content of 5 to 15 percent or less in the particle size control section.

GEOGRAPHIC SETTING:
Parent material: calcareous local alluvium derived from glacial till
Landform: depressions
Slopes: less than 1 percent
Elevation: 800 to 1500 feet above sea level
Mean annual air temperature: 45 to 53 degrees F
Mean annual precipitation: 26 to 32 inches
Frost-free period: 145 to 170 days

GEOGRAPHICALLY ASSOCIATED SOILS: Canisteo and Harps soils are the most commonly associated soils. They have mollic epipedons less than 24 inches thick. In many places Canisteo and Harps soils form a convex shoreline rim around the Knoke soils.

DRAINAGE AND PERMEABILITY:
Drainage class: very poorly drained - in undrained conditions, soil saturation occurs at the surface in normal years.
Permeability: moderately slow
Surface runoff: negligible
This soil is subject to ponding.

USE AND VEGETATION: Where drained, these areas are cultivated. The principal crops are corn, soybeans, and small grain. Reed canarygrass commonly dominates partially drained pasture. The native vegetation is herbaceous marsh species tolerant of excessive wetness such as, cattails, bulrushes, giant burreed, giant reed grass and hydrophytic sedges

DISTRIBUTION AND EXTENT: MLRA-103. Central and north-central Iowa and Southern Minnesota. Moderate extent.

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

SERIES ESTABLISHED: Calhoun County, Iowa, 1979.

REMARKS: Most of these soils were included with Okoboji soils in previous surveys.

---

National Cooperative Soil Survey
U.S.A.