LOCATION ZOOK IA+IL KS MN MO NEEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Cumulic Vertic Endoaquolls
TYPICAL PEDON: Zook silty clay loam, on a slope of less than 1 percent, in a cultivated field, at an elevation of about 351 meters above sea level. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 18 centimeters; black (10YR 2/1) silty clay loam, very dark gray (10YR 3/1) dry; weak fine subangular blocky structure parting to weak fine granular; friable; slightly acid; abrupt smooth boundary.
A1--18 to 36 centimeters; black (10YR 2/1) silty clay loam, very dark gray (10YR 3/1) dry; weak fine subangular blocky structure parting to weak fine granular; friable; slightly acid; gradual smooth boundary.
A2--36 to 51 centimeters; black (10YR 2/1) silty clay loam, very dark gray (10YR 3/1) dry; moderate fine prismatic structure parting to moderate fine subangular blocky; firm; neutral; gradual smooth boundary.
A3--51 to 79 centimeters; very dark gray (10YR 3/1) silty clay, dark gray (10YR 4/1) dry; moderate medium prismatic structure parting to moderate fine subangular blocky; firm; neutral; gradual smooth boundary.
A4--79 to 97 centimeters; very dark gray (10YR 3/1) silty clay, dark gray (10YR 4/1) dry; moderate medium prismatic structure parting to moderate medium subangular blocky; firm; common fine distinct olive gray (5Y 4/2) redoximorphic depletions; neutral; gradual smooth boundary. (Combined thickness of the A horizon is 65 to 125 centimeters.)
Bg--97 to 132 centimeters; dark gray (5Y 4/1) silty clay loam; moderate medium prismatic structure parting to moderate medium subangular blocky; firm; few fine prominent strong brown (7.5YR 5/6) redoximorphic concentrations; neutral; gradual smooth boundary. (25 to 90 centimeters thick)
BCg--132 to 155 centimeters; about 70 percent dark gray (5Y 4/1) and about 30 percent gray (5Y 5/1) silty clay loam; moderate coarse prismatic structure; firm; common fine faint grayish brown (2.5Y 5/2) redoximorphic depletions; neutral; clear smooth boundary. (0 to 50 centimeters thick)
Cg--155 to 200 centimeters; olive gray (5Y 5/2) silty clay loam; massive; friable; common fine prominent very dark brown (10YR 2/2) manganese masses; common fine prominent yellowish brown (10YR 5/6) redoximorphic concentrations; neutral.
TYPE LOCATION: Major Land Resource Area (MLRA) 107B-Iowa and Missouri Deep Loess Hills, Cass County, Iowa subset; about 5 miles west of Atlantic; located about 1,800 feet east and 210 feet north of the southwest corner of section 5, T. 76 N., R. 37 W.; USGS Walnut topographic quadrangle; lat. 41 degrees 24 minutes 17 seconds N. and long. 95 degrees 7 minutes 52 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon--90 to more than 150 centimeters
Depth to redoximorphic concentrations--60 to 150 centimeters
Depth to carbonates--150 to more than 200 centimeters
Clay content in the particle-size control section (weighted average)--35 to 45 percent
Sand content in the particle-size control section (weighted average)--0 to 15 percent fine sand and sand coarser than fine sand
Sodium adsorption ratio--0
Rock fragment content--0 percent
These soils are not stratified in the zone from the surface of the soil to a depth of 1.2 meters
Ap and A horizons:
Hue--10YR or is neutral
Value--2 or 3
Chroma--0 or 1
Texture--silty clay loam or silty clay
Clay content--32 to 45 percent
Sand content--less than 15 percent
Reaction--moderately acid to slightly alkaline
Matrix value of 3 or less extends to depths of more than 90 centimeters
Overwash phase (when present):
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--silt loam
Clay content--20 to 26 percent
Sand content--5 to 20 percent
Reaction--moderately acid to slightly alkaline
Thickness--15 to 50 centimeters
Bg horizon:
Hue--10YR to 5Y
Value--2 to 5
Chroma--1
Texture--silty clay loam or silty clay
Clay content--35 to 45 percent
Sand content--less than 15 percent
Reaction--slightly acid or neutral
BCg (when present) or Cg horizon:
Hue--10YR to 5Y
Value--2 to 5
Chroma--1 or 2
Texture--silty clay loam, silty clay, or silt loam
Clay content--20 to 45 percent
Sand content--less than 15 percent
Reaction--slightly acid or neutral
COMPETING SERIES: These are the
Chehalem,
Clamo,
Derrynane,
Okoboji,
Peotone,
Rantoul,
Shiloh,
Southbrook,
Wabash, and
Zoe series.
Chehalem--have matrix chroma of 2 or 3 in the particle-size control section and have a rock fragment content of 0 to 5 percent gravel and 0 to 35 percent paragravel in the lower third of the series control section
Clamo--have carbonates within a depth of 75 centimeters
Derrynane--have a sand content of more than 30 percent in the lower one fourth of the series control section and have a rock fragment content of 2 to 8 percent in the lower third of the series control section
Okoboji--have carbonates within a depth of 150 centimeters
Peotone--have a mollic epipedon 60 to 90 centimeters thick
Rantoul--have a mollic epipedon 60 to 90 centimeters thick, have carbonates within a depth of 150 centimeters, and have a clay content that averages 45 to 60 percent in the particle-size control section
Shiloh--are in areas that have a mean annual precipitation range of 91 to 109 centimeters and have a mollic epipedon 60 to 90 centimeters thick
Southbrook--have a sand content of more than 70 percent in the lower third of the series control section
Wabash--have a clay content that averages 45 to 60 percent in the particle-size control section
Zoe--have carbonates within a depth of 60 centimeters, do not have a cambic horizon and have a sodium adsorption ratio of 4 to 10 within a depth of 30 centimeters
GEOGRAPHIC SETTING:
Parent material--alluvium
Landform--flood plains and stream terraces in river valleys and in drainageways on uplands
Slope--0 to 5 percent
Elevation--100 to 575 meters above sea level
Mean annual air temperature--6 to 17 degrees C
Mean annual precipitation--585 to 1,220 millimeters
Frost-free period--145 to 255 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Bremer,
Judson,
Nodaway, and
Wabash soils.
Bremer--are at slightly higher elevations, have a mollic epipedon 60 to 90 centimeters thick, and have an argillic horizon
Judson--are at higher elevations on footslopes, have a clay content of 30 to 35 percent in the particle-size control section, and do not have a saturated zone within a depth of 1.8 meters during in the wettest period of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Nodaway--are at slightly higher elevations and do not have a mollic epipedon
Wabash--are in landscape positions similar to those of the Zook soils and have a clay content that averages 45 to 60 percent in the particle-size control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--poorly drained--these soils are frequently saturated from the soil surface to a depth of 0.3 meter during the wettest periods of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Saturated hydraulic conductivity--0.10 to 1.00 micrometers per second
Flooding--rare to frequent flooding for brief to long periods on floodplains or on stream terraces, and none to very frequent flooding in drainageways on uplands for brief to very brief duration
USE AND VEGETATION:
Where drained, most areas are cultivated. The principal crops are corn and soybeans. The native vegetation is big bluestem, western wheatgrass, sedges, blue grama and other species of the tall grass prairie that are tolerant of excessive wetness.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Western lake section, Wisconsin driftless section, Till plains, Dissected till plains, Osage plain
MLRAs--Till Plains (102B),
Central Iowa and Minnesota Till Prairies (103),
Eastern Iowa and Minnesota Till Prairies (104),
Northern Mississippi Valley Loess Hills (105),
Nebraska and Kansas Loess-Drift Hills (106),
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),
Cherokee Prairies (112),
Central Claypan Areas (113),
Southern Illinois and Indiana Thin Loess and Till Plain (114), and
Central Mississippi Valley Wooded Slopes (115)
Local physiographic location--commonly some distance from the main stream channel adjacent to foot slopes or terrace escarpments, in places, Zook soils are dissected by tributary channels that dissect the flood plains
LRR M; Iowa, central Illinois, northern Missouri, eastern Nebraska, south central Minnesota, and eastern Kansas
Extent--large
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Monona County, Iowa, 1956.
REMARKS:
Particle-size control section--the zone from a depth 25 to 100 centimeters;
series control section--the zone from the surface to a depth of 155 centimeters.
Diagnostic horizons and features recognized in this pedon include:
mollic epipedon--the zone from the surface to a depth 97 centimeters (Ap, A1, A2, A3, and A4 horizons);
cambic horizon--the zone from a depth of 97 to 155 centimeters (Bg and BCg horizons);
aquic moisture regime.
Vertic subgroup based on linear extensibility greater than 6.0 centimeters between the surface and a depth of 100 centimeters.
Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.
ADDITIONAL DATA:
Laboratory data--Iowa State University, Ames, Iowa
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska-user pedon ids S71IA-185-001, S96IA-193-021, and S97-047-006L (http://ssldata.sc.egov.usda.gov/).