LOCATION ARMSTRONG               IA+MO

Established Series
Rev. JAL-MRL-DJP
08/2017

ARMSTRONG SERIES

The Armstrong series consists of very deep, somewhat poorly drained soils formed in 25 to 50 centimeters of hillslope sediments or loess and in the underlying paleosol weathered from till. These soils are on side slopes and summits of interfluves on till plains. Slope ranges from 2 to 25 percent. Mean annual air temperature is about 11 degrees C. Mean annual precipitation is about 940 millimeters.

TAXONOMIC CLASS: Fine, smectitic, mesic Aquertic Hapludalfs

TYPICAL PEDON: Armstrong loam, on a west-facing, convex slope of 6 percent in a meadow. (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; moderate fine granular structure; friable; many fine roots; slightly acid; abrupt smooth boundary. (15 to 23 centimeters thick)

E--18 to 28 centimeters; grayish brown (10YR 5/2) loam; moderate thin platy structure; friable; common fine roots; few very dark grayish brown (10YR 3/2) organic stains on horizontal faces of peds; moderately 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; few fine roots; common distinct very dark grayish brown (10YR 3/2) organic stains on faces of peds; 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; friable; few fine roots; common faint brown (7.5YR 4/3) clay films on faces of peds; few distinct very dark grayish brown (10YR 3/2) organic stains on faces of peds; common prominent gray (10YR 6/1) dry silt coats on faces of peds; common fine and medium faint reddish brown (5YR 4/4) and few fine distinct yellowish red (5YR 4/6) redoximorphic concentrations; few fine distinct dark grayish brown (10YR 4/2) redoximorphic depletions; stone line at base of horizon; strongly acid; gradual smooth boundary. (0 to 20 centimeters thick)

2Bt2--46 to 66 centimeters; brown (7.5YR 4/4) clay; moderate fine subangular blocky structure; very firm; few fine roots; many distinct brown (10YR 4/3) clay films on faces of peds; many prominent gray (10YR 6/1) dry silt coats on faces of peds; few fine prominent red (2.5YR 4/6) redoximorphic concentrations; common medium distinct dark grayish brown (10YR 4/2) redoximorphic depletions; about 3 percent rock fragments; very strongly acid; gradual smooth boundary.

2Bt3--66 to 79 centimeters; strong brown (7.5YR 5/6) clay; moderate fine subangular blocky structure; very firm; few fine roots; common distinct brown (7.5YR 5/3) 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; common medium prominent light brownish gray (10YR 6/2) redoximorphic depletions; about 3 percent rock fragments; strongly acid; gradual smooth boundary.

2Bt4--79 to 122 centimeters; strong brown (7.5YR 5/6) clay loam; weak fine prismatic structure parting to moderate medium subangular blocky; very firm; few fine roots; common distinct brown (7.5YR 5/3) clay films on faces of peds and on surfaces along root channels; black (N 2.5/) organic stains on vertical faces of peds; common fine black (N 2.5/) iron-manganese concretions (oxides); common faint yellowish red (5YR 4/6) redoximorphic concentrations; common fine prominent light brownish gray (10YR 6/2) redoximorphic depletions; about 3 percent rock fragments; strongly acid; gradual smooth boundary.

2Bt5--122 to 152 centimeters; yellowish brown (10YR 5/6) and grayish brown (10YR 5/2) clay loam; weak medium prismatic structure parting to moderate medium subangular blocky; firm; few fine roots; common distinct brown (10YR 5/3) clay films on faces of peds and on surfaces along root channels; common fine black (N 2.5/) concretions (oxides); few fine prominent gray (10YR 6/1) redoximorphic depletions; about 3 percent rock fragments; moderately acid; gradual smooth boundary. (Combined thickness of the 2Bt horizon is 45 to 130 centimeters.)

2BC--152 to 175 centimeters; yellowish brown (10YR 5/6) and light brownish gray (10YR 6/2) clay loam; weak medium prismatic structure; firm; common fine black (N 2.5/) iron-manganese concretions (oxides); common fine and medium prominent gray (10YR 6/1) redoximorphic depletions; about 5 percent rock fragments; slightly acid; gradual smooth boundary.

2C--175 to 200 centimeters; yellowish brown (10YR 5/4) clay loam; massive; firm; common fine black (N 2.5/) iron-manganese concretions (oxides); few fine white (2.5Y 8/1) carbonate concretions; few fine distinct strong brown (7.5YR 5/6) redoximorphic concentrations; about 5 percent rock fragments; slightly alkaline.

TYPE LOCATION: Major Land Resource Area (MLRA) 109-Iowa and Missouri Heavy Till Plain, Appanoose County, Iowa; 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 sec. 13, T. 67 N., R. 16 W.; USGS Coatsville topographic quadrangle; lat. 40 degrees 36 minutes 05 seconds N. and long. 92 degrees 38 minutes 35 seconds W., NAD 83.

RANGE IN CHARACTERISTICS:
Depth to carbonates--100 to more than 200 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 pebble band, 2 to 13 centimeters thick that is often present at the upper boundary of the subhorizon with the highest clay content

Ap or A horizon:
Hue--10YR
Value--3
Chroma--1 or 2
Texture--loam, clay loam, silty clay loam, or silt loam
Clay content--15 to 35 percent
Sand content--10 to 45 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 26 percent
Sand content--10 to 45 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, clay loam or silty clay loam
Clay content--20 to 35 percent
Sand content--10 to 45 percent
Reaction--strongly acid to neutral

Bt horizon (when present):
Hue--7.5YR or 10YR
Value--4 or 5
Chroma--2 to 6
Texture--silty clay loam, clay loam, or loam
Clay content--25 to 40 percent
Sand content--15 to 45 percent
Coarse fragment content--0 to 10 percent
Reaction--strongly acid to slightly acid

A stone line is common at the lower boundary of the Bt horizon.

2Bt horizon:
Hue--5YR to 2.5Y
Value--4 to 6
Chroma--2 to 6
Texture--clay loam or clay
Clay content--28 to 60 percent
Sand content--25 to 45 percent
Rock fragment content--2 to 14 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--loam or clay loam
Clay content--20 to 35 percent
Sand content--30 to 45 percent
Rock fragment content--2 to 14 percent
Reaction--moderately acid to slightly alkaline

COMPETING SERIES:
These are the Clafork, Malmo, Mystic, Otoe, Pering, and Rathbun 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 average less than 30 percent sand in the particle-size control section.
Otoe--average less than 30 percent sand in the particle-size control section.
Pering--average less than 30 percent sand in the particle-size control section.
Rathbun--average less than 30 percent sand in the particle-size control section.

GEOGRAPHIC SETTING:
Parent material--25 to 50 centimeters of sediments or loess and the underlying paleosol weathered from till
Landform--side slopes and summits of interfluves on till plains
Slope--2 to 25 percent
Elevation--100 to 475 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 on lower landscape positions, have a clay content that averages 30 to 35 percent in the particle-size control section, and do not have a frequently saturated zone within a depth of 1.0 meter
Kniffin--are on slightly higher landscape positions and have a sand content of less than 10 percent in the series control section
Ladoga--are on slightly higher landscape positions and have a sand content that averages less than 5 percent in the particle-size control section
Lindley--are on 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 between depths of 0.3 and 1.0 meter during the wettest periods of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation, and this saturation is considered perched
Saturated hydraulic conductivity--0.01 to 10.00 micrometers per second

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, or 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 and LRUs--Iowa and Missouri Deep Loess Hills (107B); Illinois and Iowa Deep Loess and Drift, West-Central part (108C); Illinois and Iowa Deep Loess and Drift, Western part (108D); Iowa and Missouri Heavy Till Plain (109); Central Claypan Areas (113); Central Mississippi Valley Wooded Slopes, Western part (115B); and Central Mississippi Valley Wooded Slopes, Northern part (115C).
LRR M; southern Iowa and northern Missouri.
Extent--large

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana.

SERIES ESTABLISHED:
Appanoose County, Iowa, 1970.

REMARKS:
Diagnostic horizons and features recognized in this pedon include:
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 (Ap, E, BE, Bt1, 2Bt2, 2Bt3, 2Bt4, and 2Bt5horizons).
Ochric epipedon--the zone from the surface to a depth of 36 centimeters (Ap, E, and BE horizons);
Argillic horizon--the zone from a depth of 36 to 152 centimeters (Bt1, 2Bt2, 2Bt3, 2Bt4, and 2Bt5 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.

This series is considered a benchmark soil in MLRA 109 - Iowa and Missouri Heavy Till Plain.

Taxonomy version--Keys to Soil Taxonomy, Twelfth Edition, 2014.

ADDITIONAL DATA:
Laboratory data--Kellogg Soil Survey Laboratory, Lincoln, Nebraska pedon S87MO-121-031.

---

National Cooperative Soil Survey
U.S.A.