LOCATION ARMSTRONG IA+MOEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aquertic Hapludalfs
TYPICAL PEDON: Armstrong loam, on a west-facing, convex slope of 6 percent, in a meadow, at an elevation of about 290 meters above sea level. (Colors are for moist soil unless otherwise stated).
Ap--0 to 18 centimeters; very dark grayish brown (10YR 3/2) loam, grayish brown (10YR 5/2) dry; mixing of brown (10YR 4/3); weak fine granular structure; friable; slightly acid; abrupt smooth boundary. (15 to 25 centimeters thick)
E--18 to 28 centimeters; grayish brown (10YR 5/2) loam; about 10 percent of the peds are very dark grayish brown (10YR 3/2); moderate thin platy structure; friable; strongly acid; clear smooth boundary. (0 to 15 centimeters thick)
BE--28 to 36 centimeters; dark yellowish brown (10YR 4/4) clay loam; weak fine subangular blocky structure; friable; common distinct gray (10YR 6/1) dry silt coats on faces of peds; strongly acid; clear smooth boundary. (0 to 20 centimeters thick)
Bt1--36 to 46 centimeters; brown (7.5YR 4/4) clay loam; moderate fine subangular blocky structure; firm; few distinct clay films; common distinct gray (10YR 6/1) dry silt coats on faces of peds; few fine faint reddish brown (5YR 4/4) and few fine distinct yellowish red (5YR 4/6) redoximorphic concentrations; stone line at base of horizon; strongly acid; gradual smooth boundary. (0 to 20 centimeters thick)
2Bt2--46 to 66 centimeters; mottled brown (7.5YR 4/4) and dark grayish brown (10YR 4/2) clay; moderate fine subangular blocky structure; very firm; many distinct clay films on faces of peds; many distinct gray (10YR 6/1) dry silt coats on faces of peds; few fine prominent red (2.5YR 4/6) redoximorphic concentrations; some pebbles; very strongly acid; gradual smooth boundary.
2Bt3--66 to 79 centimeters; mottled strong brown (7.5YR 5/6) and light brownish gray (10YR 6/2) clay; moderate fine subangular blocky structure; very firm; common distinct clay films on faces of peds; few fine prominent dark red (2.5YR 3/6) and common medium faint yellowish red (5YR 4/6) redoximorphic concentrations; some pebbles; strongly acid; gradual smooth boundary.
2Bt4--79 to 104 centimeters; strong brown (7.5YR 5/6) clay loam; moderate fine prismatic structure parting to weak medium subangular blocky; very firm; few distinct clay films on faces of peds and on surfaces along root channels; black (N 2/0) organic material on vertical ped faces; common fine black concretions (oxides); common fine prominent light brownish gray (10YR 6/2) and yellowish red (5YR 4/6) redoximorphic concentrations; common pebbles; strongly acid; gradual smooth boundary. (Combined thickness of the 2Bt horizon is 45 to 102 centimeters.)
2BC--104 to 152 centimeters; yellowish brown (10YR 5/6) clay loam; weak medium prismatic structure parting to weak medium subangular blocky; firm; few dark brown clay flows on surfaces along root channels; common fine black concretions (oxide); common fine and medium prominent gray (10YR 6/1) redoximorphic concentrations; moderately acid.
TYPE LOCATION: Major Land Resource Area (MLRA) 109-Iowa and Missouri Heavy Till Plain, Appanoose County, Iowa subset; about 6 miles south and 1 mile east of Moulton; located about 2,250 feet north and 1,370 feet west of the southeast corner of section 13, T. 67 N., R. 16 W.; USGS Coatsville topographic quadrangle; lat. 40 degrees 36 minutes 06 seconds N. and long. 92 degrees 38 minutes 34 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Depth to carbonates--100 to 203 centimeters
Clay content in the particle-size control section (weighted average)--35 to 60 percent
Sand content in the particle-size control section (weighted average)--30 to 45 percent
Special feature--some pedons have a stone line or thin layer, 2 to 13 centimeters thick, of gravelly and sandy materials at the base of the silty or loamy sediments
Ap or A horizon:
Hue--10YR
Value--3
Chroma--1 or 2
Texture--loam, clay loam, silty clay loam, or silt loam
Clay content--20 to 35 percent
Sand content--10 to 50 percent
Reaction--moderately acid to neutral
E horizon (when present):
Hue--10YR
Value--4 or 5
Chroma--2 or 3
Texture--loam or silt loam
Clay content--18 to 27 percent
Sand content--15 to 50 percent
Reaction--moderately acid to neutral
Some pedons have an EB horizon
BE horizon (when present):
Hue--10YR
Value--4 or 5
Chroma--2 to 4
Texture--loam or clay loam
Clay content--20 to 35 percent
Sand content--25 to 45 percent
Reaction--moderately acid to neutral
Bt horizon (when present):
Hue--7.5YR or 10YR
Value--4 or 5
Chroma--2 to 6
Texture--loam or clay loam
Clay content--25 to 35 percent
Sand content--25 to 45 percent
Rock fragment content--1 to 10 percent - a stone line is commonly at the lower boundary of this horizon
Reaction--moderately acid to neutral
2Bt horizon:
Hue--5YR, 7.5YR, 10YR, or 2.5Y
Value--4 or 5
Chroma--2 to 6
Texture--clay loam or clay
Clay content--35 to 60 percent
Sand content--30 to 45 percent
Rock fragment content--2 to 15 percent
Reaction--very strongly acid to slightly acid
2BC or 2C horizon:
Hue--10YR or 2.5Y
Value--4 to 6
Chroma--2 to 6
Texture--clay loam
Clay content--27 to 35 percent
Sand content--30 to 45 percent
Rock fragment content--2 to 15 percent
Reaction--moderately acid to slightly alkaline
COMPETING SERIES: These are the
Clafork,
Malmo,
Mystic,
Otoe, and
Pering series.
Clafork--have brittle horizons in the lower third of the series control section
Malmo--have carbonates within a depth of 100 centimeters
Mystic--do not have a stone line in the upper part of the series control section and are typically stratified in the lower third of the series control section
Otoe--have a sand content that averages 1 to 10 percent in the particle-size control section and have carbonates within a depth of 127 centimeters
Pering--have a sand content that averages less than 10 percent in the particle-size control section and do not have carbonates in the series control section
GEOGRAPHIC SETTING:
Parent material--25 to 50 centimeters of sediments or loess and the underlying paleosol weathered from till
Landform--summits of interfluves and side slopes on till plains
Slope--2 to 25 percent
Elevation--200 to 400 meters above sea level
Mean annual air temperature--8 to 14 degrees C
Mean annual precipitation--660 to 1,220 millimeters
Frost-free period--155 to 230 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Gara,
Kniffin,
Ladoga, and
Lindley soils.
Gara--are at lower landscape positions and have a clay content that averages 30 to 35 percent in the particle-size control section
Kniffin--are at slightly higher landscape positions and have a sand content of less than 10 percent in the series control section
Ladoga--are at slightly higher landscape positions and have a sand content that averages less than 5 percent in the particle-size control section
Lindley--are at lower landscape positions and have a clay content that averages less than 35 percent in the particle-size control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs at a depth of 0.3 meter during March to June in normal years and is considered perched
Saturated hydraulic conductivity--0.10 to 1.00 micrometers per second
Surface runoff potential--medium to very high
USE AND VEGETATION:
Most areas are pastured. Some areas are cultivated. The principal crops are hay, corn, and small grains. The native vegetation is mixed big bluestem, little bluestem, switchgrass, other grasses of the tall grass prairie and deciduous trees.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Dissected till plains, Till plains
MLRAs--Iowa and Missouri Deep Loess Hills (107),
Illinois and Iowa Deep Loess and Drift (108),
Iowa and Missouri Heavy Till Plain (109),
Central Clay Pan Areas (113), and
Central Mississippi Valley Wooded Slopes (115)
LRR M; southern Iowa and northern Missouri
Extent--large
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Appanoose County, Iowa, 1970.
REMARKS:
Particle-size control section--the zone from a depth of 36 to 86 centimeters (Bt1, 2Bt2, 2Bt3, and 2Bt4 horizons);
series control section--the zone from the surface to a depth of 150 centimeters.
Diagnostic horizons and features recognized in this pedon include:
ochric epipedon--the zone from the surface to a depth of 36 centimeters (A, E, and BE horizons);
argillic horizon--the zone from a depth of 36 to 104 centimeters (Bt1, 2Bt2, 2Bt3, and 2Bt4 horizons);
udic moisture regime.
Aquertic subgroup based on colors within the upper 25 centimeters of the argillic horizon and 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--National Soil Survey Laboratory, Lincoln, Nebraska pedon S87MO-121-031 (http://ssldata.sc.egov.usda.gov/).