LOCATION WALNUT GROVE MNEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Aquic Hapludolls
TYPICAL PEDON: Walnut Grove clay loam, on a linear slope of about 2 percent, on a ground moraine, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 centimeters; black (10YR 2/1) clay loam, very dark gray (10YR 3/1) dry; weak very fine and fine subangular blocky structure; friable; about 4 percent gravel; moderately acid; abrupt smooth boundary.
A--20 to 36 centimeters; black (10YR 2/1) clay loam, very dark gray (10YR 3/1) dry; weak fine subangular blocky structure; friable; about 3 gravel; slightly acid; clear wavy boundary.
Bw1--36 to 46 centimeters; dark grayish brown (2.5Y 4/2) clay loam; very dark grayish brown (2.5Y 3/2) crushed; moderate very fine subangular blocky structure; friable; very dark gray (10YR 3/1) worm casts; about 3 percent gravel; neutral; clear wavy boundary.
Bw2--46 to 71 centimeters; olive brown (2.5Y 4/4) clay loam; very dark grayish brown (2.5Y 3/2) crushed; moderate fine and medium subangular blocky structure; friable; few fine faint grayish brown (2.5Y 5/2) iron depletions; about 3 percent gravel; neutral; clear smooth boundary.
Bk--71 to 99 centimeters; light olive brown (2.5Y 5/4) clay loam; weak fine and very fine subangular blocky structure; firm; about 15 percent disseminated calcium carbonates; many fine faint grayish brown (2.5Y 5/2) iron depletions; about 4 percent gravel; strongly effervescent; moderately alkaline; gradual smooth boundary.
BC1--99 to 152 centimeters; light yellowish brown (2.5Y 6/4) clay loam; moderate coarse prismatic structure parting to moderate medium angular blocky; firm; few concentrations of iron and manganese; many coarse distinct grayish brown (2.5Y 5/2) iron depletions; about 8 percent gravel; strongly effervescent; moderately alkaline; gradual wavy boundary.
BC2--152 to 203 centimeters; light olive brown (2.5Y 5/4) clay loam; moderate coarse prismatic structure parting to moderate medium angular blocky; firm; few concentrations of iron and manganese; many coarse distinct gray (2.5Y 6/1) iron depletions; about 8 percent gravel; strongly effervescent; moderately alkaline.
TYPE LOCATION: Major Land Resource Area (MLRA) 103-Central Iowa and Minnesota Till Prairies, Redwood County, Minnesota subset; about 1.4 miles south of Walnut Grove; about 1,870 feet south and 350 feet east of the northwest corner of section 31, T. 109 N., R. 38 W.; USGS Walnut Grove topographic quadrangle, lat. 44 degrees 12 minutes 20 seconds N. and long. 95 degrees 28 minutes 21 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness--35 to 60 centimeters
Depth to carbonates--50 to 100 centimeters
Clay content of the particle-size control section (weighted average)--24 to 35 percent
Sand content in particle-size control section (weighted average)--18 to 40 percent
Rock fragment content--1 to 8 percent, mixed lithology
The moist consistency is friable or firm in the upper third of the series control section
Ap or A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--clay loam, silty clay loam, or loam
Clay content--24 to 35 percent
Sand content--18 to 40 percent
Reaction--pH 6.1 to 7.3
Moist bulk density--1.35 to 1.55 g/cc
Thickness--15 to 60 centimeters
AB or BA horizon (when present):
Hue--10YR
Value--2 or 3
Chroma--1 to 3
Texture--clay loam or loam
Clay content--24 to 35 percent
Sand content--20 to 40 percent
Reaction--pH 6.1 to 7.3
Moist bulk density--1.35 to 1.55 g/cc
Thickness--0 to 20 centimeters
Bw horizon:
Hue--10YR or 2.5Y
Value--3 to 5
Chroma--2 to 4
Texture--clay loam, loam, or sandy clay loam
Clay content--24 to 35 percent
Sand content--20 to 50 percent
Reaction--pH 6.1 to 7.8
Moist bulk density--1.35 to 1.55 g/cc
Thickness--15 to 60 centimeters
Some pedons have Bt horizons with clay films present on ped faces, however these horizons do not meet the clay increase of 1.2 percent from the eluvial horizon requirement for an argillic horizon
Bk horizon:
Hue--10YR or 2.5Y
Value--5 or 6
Chroma--2 to 4
Texture--clay loam or loam
Clay content--24 to 35 percent
Sand content--20 to 40 percent
Reaction--pH 7.4 to 8.4
Calcium carbonate equivalent--15 to 30 percent; 5 percent or more higher than the underlying horizon(s)
Moist bulk density--1.45 to 1.65 g/cc
Thickness--8 to 40 centimeters
BC or C horizon:
Hue--10YR or 2.5Y
Value--5 or 6
Chroma--2 to 4
Texture--clay loam or loam
Clay content--24 to 35 percent
Sand content--20 to 40 percent
Reaction--pH 7.4 to 8.4
Calcium carbonate equivalent--10 to 20 percent
Moist bulk density--1.45 to 1.65 g/cc
The moist consistency of the BC or C horizons is typically firm
COMPETING SERIES: These are the
Arkton,
Crippin,
Fostoria,
Kensett,
Merton,
Nicollet,
Normania,
Ottosen,
Readlyn,
Snider,
Stone, and
Wilmonton series.
Arkton--have carbonates within a depth of 50 centimeters
Crippin--have carbonates within a depth of 25 centimeters
Fostoria--do not rock fragments in the series control section
Kensett--have a lithic contact with limestone within a depth of 100 centimeters
Merton--have a sand content of 45 to 70 percent in the lower third of the series control section
Nicollet--have a moist bulk density range of 1.35 to 1.55 g/cc in the lower third of the series control section and have a clay content of 12 to 30 percent in the lower third of the series control section
Normania--have a moist bulk density range of 1.40 to 1.50 g/cc in the lower third of the series control section and have a clay content of 18 to 32 percent in the lower half of the series control section
Ottosen--have a clay content that averages 30 to 35 percent in the particle-size control section
Readlyn--do have carbonates within a depth 100 centimeters and have a moist bulk density range of 1.75 to 1.90 g/cc in the lower third of the series control section
Snider--do not have rock fragments in the series control section
Stone--have a lithic contact with limestone within a depth of 100 centimeters
Wilmonton--have a moist bulk density of 1.25 to 1.45 g/cc in the upper third of the series control section, see remarks
GEOGRAPHIC SETTING:
Parent material--calcareous, loamy till
Landform--slightly concave to slightly convex slopes on ground moraines and till plains (Coteau Slope)
Slope--0 to 3 percent
Elevation--300 to 400 meters above sea level, see remarks
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
Annton,
Belview,
North Twin,
Pell Creek,
Romnell, and
Storden soils.
Annton--are on higher landscape positions on convex slopes and do not have a frequently saturated zone within a depth of 1 meter during the wettest periods of years when precipitation is within one standard deviation of 30 year mean of annual precipitation
Belview and Storden--are on higher landscape positions on convex slopes and have carbonates throughout the series control section
North Twin--are on slightly higher landscape positions and have a frequently saturated zone between depths of 0.6 to 1.0 meter during the wettest periods of years when precipitation is within one standard deviation of 30 year mean of annual precipitation
Pell Creek--are on slightly lower landscape positions and have a frequently saturated zone between depths of 0.15 and 0.45 meter during the wettest periods of years when precipitation is within one standard deviation of 30 year mean of annual precipitation
Romnell--are on lower landscape positions in depressions, swales, and drainageways and are frequently saturated at the soil surface to a depth of 0.15 meter during the wettest periods of years when precipitation is within one standard deviation of 30 year mean of annual precipitation
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs between depths of 0.45 and 0.6 meters during the wettest periods of years when precipitation is within one standard deviation of 30 year mean of annual precipitation, this saturation is both perched and apparent
Saturated hydraulic conductivity--1.00 to 10.00 micrometers per second
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, legume hay, small grains, and soybeans. The native vegetation is big bluestem, little bluestem, switchgrass, and other grasses of the tall grass prairie.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic Section--Western lake section
Local physiographic area--Coteau des Prairies bench" geomorphic surface
MLRA--Central Iowa and Minnesota Till Prairies (103)
LRR--M; south-central and southwestern Minnesota
Extent--moderate
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota; MLRA SSO 10-5 (Albert Lea, Minnesota).
SERIES ESTABLISHED: Cottonwood County, Minnesota, 2009.
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 properties recognized in this pedon are:
mollic epipedon--the zone from the surface to a depth of 36 centimeters (Ap and A horizons);
cambic horizon--the zone from a depth of 36 to 71 and the zone from a depth of 99 to 203 centimeters (Bw1, Bw2, BC1, and BC2 horizons);
calcic horizon--the zone from 71 to 99 centimeters (Bk horizon);
udic moisture regime.
Some pedons have a sandy or coarse-loamy lag line about 10 centimeters thick with or without gravel at the base of the solum.
These soils were previously identified as Wilmonton soils on the Coteau des Prairies "bench" geomorphic landform.
The differentia between Walnut Grove and Wilmonton series needs further study.
The BC horizon is defined by having prismatic primary structure parting to angular or subangular blocky. This structure is evident in pits and cutbanks and rarely observed by by smaller scale investigations. The change in moist bulk density of 1.45 to 1.65 g/cc was based on some lab data of similar soils and field investigations by soil scientists on this geomorphic landform.
Based on current investigations, elevation ranges in MLRA 103 is about 270 to 480 meters above sea level. However, the elevation data in the 2006 issue of USDA Handbook 296, has not been changed to agree with this elevation data.
Cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.