LOCATION SEYMOUR IA+MO
Established Series
Rev. JDH-JES-TWN
04/2011
SEYMOUR SERIES
The Seymour series consists of very deep, somewhat poorly drained soils formed in loess. These soils are on convex ridgetops and side slopes on dissected till plains and on treads on stream terraces in river valleys. Slope ranges from 2 to 9 percent. Mean annual temperature is about 11 degrees C. Mean annual precipitation is about 950 millimeters.
TAXONOMIC CLASS: Fine, smectitic, mesic Aquertic Argiudolls
TYPICAL PEDON: Seymour silt loam, on a convex, north-facing slope of 2 percent, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 centimeters; very dark gray (10YR 3/1) silt loam, gray (10YR 5/1) dry; weak fine subangular blocky structure parting to weak fine granular; friable; many fine roots; very few very fine dark brown (10YR 3/3) accumulations (oxides); slightly acid; abrupt smooth boundary.
A1--20 to 28 centimeters; very dark gray (10YR 3/1) and some very dark grayish brown (10YR 3/2) silt loam, gray (10YR 5/1) dry; weak very fine subangular blocky and weak fine granular structure; friable; many fine roots; few krotovinas; common very fine dark brown (10YR 3/3) and black (10YR 2/1) concretions (oxides); moderately acid; clear smooth boundary.
A2--28 to 38 centimeters; very dark gray (10YR 3/1) and about 20 percent very dark grayish brown (10YR 3/2) silty clay loam, grayish brown (10YR 5/2) dry; moderate very fine subangular blocky structure; friable; many fine roots; few very fine dark brown (10YR 3/3) and black (10YR 2/1) accumulations (oxides); moderately acid; clear smooth boundary.
BAg--38 to 48 centimeters; dark grayish brown (2.5Y 4/2) silty clay loam, light brownish gray (10YR 6/2) dry; moderate very fine subangular blocky structure; firm; common fine roots; fine dark brown (10YR 3/3) and black (10YR 2/1) spherical iron-manganese concretions; few fine distinct light olive brown (2.5Y 5/4) masses of oxidized iron; moderately acid; clear smooth boundary.
Btg1--48 to 58 centimeters; dark grayish brown (10YR 4/2) silty clay; strong very fine subangular blocky structure; firm; few fine roots; common distinct dark gray (10YR 4/1) clay films on all faces of peds; common very fine dark brown (10YR 3/3) and black (10YR 2/1) spherical iron-manganese concretions; common fine distinct dark yellowish brown (10YR 4/4) and many fine distinct yellowish brown (10YR 5/4) masses of oxidized iron; krotovina filled with very dark gray (10YR 3/1) silty clay loam; moderately acid; clear smooth boundary.
Btg2--58 to 71 centimeters; dark grayish brown (10YR 4/2) silty clay; strong very fine angular and subangular blocky structure; firm; few fine roots; common distinct very dark gray (10YR 3/1) clay films on all faces of peds; common fine black (10YR 2/1) spherical iron-manganese concretions; few fine faint brown (10YR 4/3) masses of oxidized iron; many fine prominent yellowish brown (10YR 5/6) masses of oxidized iron; slightly acid; clear smooth boundary.
Btg3--71 to 91 centimeters; dark grayish brown (10YR 4/2) and grayish brown (2.5Y 5/2) silty clay; moderate fine and medium subangular blocky structure; firm; few distinct dark gray (10YR 4/1) clay films on all faces of peds; common fine distinct yellowish brown (10YR 5/4) masses of oxidized iron; slightly acid; clear irregular boundary.
Btg4--91 to 137 centimeters; olive gray (5Y 5/2) and some dark gray (2.5Y 4/1) silty clay loam; moderate medium subangular blocky structure; firm; common distinct dark gray (10YR 4/1) clay films on all faces of peds; common fine black (10YR 2/1) spherical iron-manganese concretions in matrix; common medium and fine prominent yellowish brown (10YR 5/6) masses of oxidized iron; neutral; gradual smooth boundary.
Btg5--137 to 163 centimeters; olive gray (5Y 5/2) and dark gray (2.5Y 4/1) silty clay loam; very weak coarse prismatic structure parting to very weak coarse angular blocky; friable; few dark gray (10YR 4/1) clay films on surfaces along pores; few fine prominent yellowish brown (10YR 5/6) and strong brown (7.5YR 5/6) masses of oxidized iron; neutral; clear smooth boundary.
BCg--163 to 174 centimeters; olive gray (5Y 5/2) and some dark gray (2.5Y 4/1) silty clay loam; weak coarse prismatic structure; friable; few fine prominent yellowish brown (10YR 5/6) and strong brown (7.5YR 5/6) masses of oxidized iron; neutral; clear smooth boundary.
Cg--174 to 200 centimeters; olive gray (5Y 5/2) silty clay loam; massive; friable; common fine prominent yellowish brown (10YR 5/6) and strong brown (7.5YR 5/6) masses of oxidized iron; neutral.
TYPE LOCATION: Major Land Resource Area (MLRA) 109-Iowa and Missouri Heavy Till Plain, Wayne County, Iowa subset; about 2 miles south of Promise City; located about 2,040 feet north and 2,172 feet east of the southwest corner of section 3, T. 68 N., R. 20 W.; USGS Seymour West topographic quadrangle; lat. 40 degrees 42 minutes 58 seconds N. and long. 93 degrees 8 minutes 47 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon--25 to 49 centimeters
Depth to carbonates--more than 200 centimeters
Clay content in the particle-size control section (weighted average)--42 to 48 percent
Sand content in the particle-size control section (weighted average)--less than 3 percent
Rock fragment content--0 percent
Ap or A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--22 to 35 percent
Sand content--less than 3 percent
Reaction--pH 5.6 to 7.3
Thickness--25 to 49 centimeters
BAg or BA (when present) horizon:
Hue--10YR or 2.5Y
Value--4
Chroma--2
Texture--silty clay loam or silty clay
Clay content--35 to 47 percent
Sand content--less than 3 percent
Reaction--pH 5.6 to 7.3
Thickness--0 to 15 centimeters
Btg horizon (upper part):
Hue--10YR or 2.5Y
Value--4 or 5
Chroma--2
Texture--silty clay or silty clay loam
Clay content--35 to 54 percent
Sand content--less than 3 percent
Reaction--pH 5.1 to 7.3
Btg horizon (lower part):
Hue--10YR to 5Y
Value--4 to 6
Chroma--1 or 2
Texture--silty clay or silty clay loam
Clay content--32 to 42 percent
Sand content--less than 3 percent
Reaction--pH 5.1 to 7.3
Thickness (entire Btg horizon)--100 to 170 centimeters
Special feature--the Btg horizon has a subhorizon with a clay content of 48 to 54 percent
BCg horizon:
Hue--2.5Y or 5Y
Value--5 or 6
Chroma--1 or 2
Texture--silty clay loam or silt loam
Clay content--22 to 35 percent
Sand content-less than 3 percent
Reaction--pH 5.6 to 7.3
Thickness--10 to 25 centimeters
Cg horizon:
Hue--2.5Y or 5Y
Value--5 or 6
Chroma--1 or 2
Texture--silty clay loam or silt loam
Clay content--22 to 35 percent
Sand content-less than 3 percent
Reaction--pH 5.6 to 7.3
COMPETING SERIES: These are the
Adair,
Arisburg,
Arispe,
Chase, Good Thunder,
Greenton,
Grundy,
Lagonda,
Lamoni,
Macksburg,
Mahaska,
Martin,
Mayberry,
Shorewood,
Tina, and
Wymore series.
Adair--have a sand content that averages 15 to 35 percent in the particle-size control section
Arisburg--does not have a subhorizon that has a clay content of 48 to 54 percent clay
Arispe--have a clay content that averages 35 to 42 percent in the particle-size control section
Chase--have a mollic epipedon greater than 90 centimeters thick
Good Thunder--have carbonates within a depth of 127 centimeters
Greenton--have shale fragments in the series control section
Grundy--does not have a subhorizon that has a clay content of 48 to 54 percent clay
Lagonda--have a sand content that averages more than 5 percent in the particle-size control section
Lamoni--have a sand content of more than 5 percent in the series control section
Macksburg--does not have a subhorizon that has a clay content of 48 to 54 percent clay
Mahaska--have a clay content that averages 35 to 42 percent in the particle-size control section
Martin--have a depth to shale or clay beds between 100 to 200 centimeters and have mollic epipedons 60 to 90 centimeters thick
Mayberry--have a sand content of more than 5 percent in the series control section
Shorewood--have carbonates within a depth of 127 centimeters
Tina--have more than 5 percent sand in the upper part of the series control section and has more than 15 percent sand in the whole soil profile
Wymore--criteria to differentiate the Wymore series are unclear and need additional study
GEOGRAPHIC SETTING:
Parent material--loess
Landform--convex ridgetops and side slopes on dissected till plains and on treads on stream terraces in river valleys
Slope--2 to 9 percent
Elevation--200 to 300 meters above sea level
Mean annual air temperature--9 to 12 degrees C
Mean annual precipitation--865 to 1,040 millimeters
Frost-free period--175 to 210 days
GEOGRAPHICALLY ASSOCIATED SOILS: Near the type location, these are
Adair,
Clarinda,
Edina,
Lagonda, and
Lamoni soils.
Adair--are at lower landscape positions and have a sand content that averages 15 to 35 percent in the particle-size control section
Clarinda--are at lower landscape positions and have a sand content that averages more than 15 percent in the particle-size control section
Edina--are at lower elevations in small depressions on interfluves, have albic horizons and have an abrupt increase in clay from the albic to the argillic horizons
Lagonda--are at lower landscape positions on side slopes and have a sand content of more than 5 percent in the lower half of the series control section
Lamoni--are on lower landscape positions and have a sand content that averages more than 15 percent in the particle-size control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs within depths of 0.3 to 1.0 meter during the wettest periods in years when precipitation is within one standard deviation of the 30 year mean of annual precipitation, this saturation is considered perched
Saturated hydraulic conductivity--0.01 to 0.10 micrometers per second
USE AND VEGETATION: Most areas are cultivated. The principal crops are corn, soybeans, and small grains. The native vegetation is big bluestem, little bluestem, indiangrass, switchgrass, and other grasses of the tall grass prairie.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Dissected till plain
MLRA--Iowa and Missouri Heavy Till Plain (109)
LRR M; southern Iowa and northern Missouri
Extent--moderate
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Wayne County, Iowa, 1952.
REMARKS:
Particle-size control section--the zone from 48 to 98 centimeters;
series control section--the zone from the surface to a depth of 163 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, A1, and A2 horizons);
argillic horizon--the zone from a depth of 48 to 163 centimeters (Btg1, Btg2, Btg3, Btg4, and Btg5 horizons);
udic moisture regime.
Aquertic subgroup based on colors within the BAg horizon and linear extensibility greater than 6.0 centimeters between the surface and a depth of 100 centimeters.
Depth to clay maximum decreases as gradient increases on convex slopes.
Differentia between the Seymour and Wymore series needs further study.
4/2011 - Update to correct Latitude .
Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.
ADDITIONAL DATA:
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska many pedons (http://ssldata.sc.egov.usda.gov/)
National Cooperative Soil Survey
U.S.A.