LOCATION EXIRA              IA
Established Series
Rev. JRN-RAL-TWN
05/2004

EXIRA SERIES


The Exira series consists of very deep, well drained soils formed in loess. These soils are on side slopes and head slopes on dissected till plains and risers on stream terraces. Slopes range from 5 to 30 percent. Mean annual air temperature is about 9 degrees C (49 degrees F). Mean annual precipitation is about 74 centimeters (29 inches).

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Hapludolls

TYPICAL PEDON: Exira silty clay loam, on a west-facing, convex slope of 7 percent, in a cultivated field, at an elevation of 350 meters (1,148 feet) above sea level. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 20 centimeters (0 to 8 inches); very dark brown (10YR 2/2) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine granular structure; friable; moderately acid; abrupt smooth boundary.

A--20 to 28 centimeters (8 to 11 inches); very dark grayish brown (10YR 3/2) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure parting to weak fine granular; friable; moderately acid; gradual smooth boundary. [Combined thickness of the A horizon is 25 to 41 centimeters (10 to 16 inches) thick.]

Bw1--28 to 46 centimeters (11 to 18 inches); brown (10YR 4/3) silty clay loam; weak fine subangular blocky structure; friable; dark brown (10YR 3/3) coatings on faces of peds and very dark grayish brown (10YR 3/2) coatings on root channels; moderately acid; gradual smooth boundary.

Bw2--46 to 56 centimeters (18 to 22 inches); brown (10YR 4/3) silty clay loam; weak fine subangular blocky structure; friable; slightly acid; gradual smooth boundary.

Bw3--56 to 76 centimeters (22 to 30 inches); brown (10YR 4/3) silty clay loam; weak medium prismatic structure parting to weak fine subangular blocky; friable; few fine dark iron-manganese concretions; few strong brown (7.5YR 5/6) iron masses; common fine faint grayish brown (10YR 5/2) relict redoximorphic depletions and few fine faint dark yellowish brown (10YR 4/4) relict redoximorphic concentrations; slightly acid; gradual smooth boundary. [Combined thickness of the Bw horizon is 30 to 56 centimeters (12 to 22 inches).]

BC--76 to 107 centimeters (30 to 42 inches); yellowish brown (10YR 5/4) silt loam; weak medium prismatic structure parting to weak fine subangular blocky; friable; few fine dark iron-manganese concretions; few yellowish red (5YR 5/8) iron masses; common fine distinct light brownish gray (2.5Y 6/2) relict redoximorphic depletions and common fine prominent strong brown (7.5YR 5/8) relict redoximorphic concentrations; slightly acid; gradual smooth boundary. [20 to 30 centimeters (8 to 12 inches) thick]

C--107 to 152 centimeters (42 to 60 inches); mottled light brownish gray (2.5Y 6/2) and brown (7.5YR 4/4) silt loam; massive; friable; many very fine dark iron-manganese concretions; neutral.

TYPE LOCATION: Major Land Resource Area (MLRA) 107; Mills County, Iowa; about 1/2 mile south of the town of Strahan; about 787 meters (2,580 feet) south and 72 meters (235 feet) west of the northeast corner of section 24, T. 71 N., R. 41 W.; USGS Tabor NE quadrangle; lat. 40 degrees 56 minutes 20 seconds N. and long. 95 degrees 30 minutes 2 seconds W., NAD 83.

RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon--25 to 41 centimeters (10 to 16 inches)
Depth to relict redoximorphic features--41 to 76 centimeters (16 to 30 inches)
Depth to carbonates--greater than 102 centimeters (40 inches)
Content of clay in the particle-size control section (weighted average)--27 to 35 percent
Content of sand in the particle-size control section (weighted average)--less than 10 percent

Ap or A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 to 3
Texture--silty clay loam
Clay content--28 to 34 percent
Sand content--less than 10 percent
Reaction--moderately acid to neutral

Some pedons have a BA horizon

Bw horizon:
Hue--10YR
Value--3 to 5
Chroma--3
Texture--silty clay loam or silt loam
Clay content--25 to 35 percent
Sand content--less than 10 percent
Reaction--moderately acid or slightly acid
Special features--common to many relict redoximorphic features are in the lower part of the Bw horizon

BC horizon:
Hue--10YR or 2.5Y
Value--5 or 6
Chroma--2 to 4
Texture--silty clay loam or silt loam
Clay content--25 to 35 percent
Sand content--less than 10 percent
Reaction--moderately acid to neutral

C horizon:
Hue--7.5YR to 2.5Y
Value--4 to 6
Chroma--2 to 6
Texture--silt loam or silty clay loam
Clay content--20 to 30 percent
Sand content--less than 10 percent
Reaction--slightly acid or neutral

COMPETING SERIES: These are the Annieville, Biggsville, Dinsmore, Galva, Keg, Marshall, Monona, Northboro, Ponca, Port Byron, Raddle, Salix, and Truman series.
Annieville--have a sand content of more than 10 percent in the lower third of the series control section and a moist bulk density range of 1.6 to 1.8 g/cc in the lower third of the series control section
Biggsville--have a clay content of less than 27 percent in the particle-size control section
Dinsmore--have a sand content of 35 to 50 percent in the lower third of the series control section and a moist bulk density range of 1.75 to 1.9 gm/cc in the lower third of the series control section
Galva--do not have redoximorphic features within a depth of 76 centimeters (30 inches)
Keg--have a clay content of 18 to 26 percent in the particle-size control section
Marshall--do not have redoximorphic features within a depth of 76 centimeters (30 inches)
Monona--do not have redoximorphic features within a depth of 76 centimeters (30 inches) and have a clay content of 20 to 30 percent in the particle-size control section
Northboro--have a sand content of more than 20 percent in the lower third of the series control section
Ponca--have carbonates within depths of 36 to 61 centimeters (14 to 24 inches)
Port Byron--have a clay content of 18 to 27 percent in the particle-size control section
Raddle--have a clay content of 18 to 24 percent in the particle-size control section
Salix--have carbonates within depths of 51 to 91 centimeters (20 to 36 inches)
Truman--have carbonates within depths of 46 to 142 centimeters (18 to 56 inches), have a clay content of 18 to 32 percent in the particle-size control section, and have a calcium carbonate equivalent range of 5 to 15 percent in the lower third of the series control section

GEOGRAPHIC SETTING:
Parent material--loess
Landform--side slopes and head slopes on dissected till plains and risers on stream terraces
Slopes--5 to 30 percent
Elevation--320 to 472 meters (1050 to 1550 feet) above sea level
Mean annual air temperature--8 to 11 degrees C (47 to 52 degrees F)
Mean annual precipitation--66 to 81 centimeters (26 to 32 inches)
Frost-free period--145 to 175 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dow, Judson, Marshall, and Strahan soils.
Dow--are in similar landscape positions to those of the Exira soils, do not have a cambic horizon, and have carbonates within a depth of 25 centimeters (10 inches)
Judson--are at lower elevations on base slopes and have a mollic epipedon 81 to 132 centimeters (32 to 52 inches) thick
Marshall--are at higher elevations on side slopes and interfluves and do not have redoximorphic features within a depth of 76 centimeters (30 inches)
Strahan--are in similar landscape positions to those of the Exira soils, do not have a cambic horizon, have a clay content of 18 to 25 percent in the particle-size control section, and have carbonates within depths of 76 to 152 centimeters (30 to 60 inches)

DRAINAGE AND PERMEABILITY:
Drainage class--well drained--saturation does not occur within a depth of 1.8 meters (6 feet) during the wettest periods of most years
Saturated hydraulic conductivity--moderately high
Surface runoff potential--medium or high

USE AND VEGETATION:
The more gently sloping areas are cultivated. The principal crops are corn, small grains, soybeans, and legume hay. The more steeply sloping areas are used for hay production or are pastured. 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(s)--Dissected till plains
MLRA--Iowa and Missouri Deep Loess Hills (107)
LRR M; west-central and southwestern Iowa
Extent--moderate

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

SERIES ESTABLISHED: Mills County, Iowa, 1979.

REMARKS:
Particle-size control section--the zone from a depth of 25 to 100 centimeters (10 to 40 inches) (A, Bw1, Bw2, Bw3, and BC horizons);
series control section--the zone from the surface to a depth of 150 centimeters (59 inches) (Ap, A, Bw1, Bw2, Bw3, BC, and C horizons).

Diagnostic horizons and features recognized in this pedon:
mollic epipedon--the zone from the surface to a depth of 28 centimeters (0 to 11 inches) (Ap, and A horizons);
cambic horizon--the zone from a depth of 28 to 107 centimeters (11 to 42 inches) (Bw1, Bw2, Bw3, and BC horizons);
udic moisture regime.

The gray colors and redoximorphic features are relict features related to a previous deoxidized and leached geological weathering zone. These colors are not indicative of present drainage conditions. These features were not considered in the classification of these soils.

Depth to relict gray colors decrease with increasing gradient on convex slopes.

Cation-exchange activity class is supported by lab data number 96IA047001, NSSL.

Taxonomy version--second edition, 1999.

ADDITIONAL DATA:
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska pedon 96IA047001 (http://ssldata.sc.egov.usda.gov/).


National Cooperative Soil Survey
U.S.A.