LOCATION AFTON IA

Established Series
Rev. CSF-JRH-RJB
06/2015

AFTON SERIES

The Afton series consists of very deep, poorly drained soils formed in 100 to more than 200 centimeters of loess and local alluvium and the underlying till. These soils are in upland drainageways on dissected till plains. Slope ranges from 0 to 2 percent. Mean annual precipitation is about 638 millimeters, and mean annual air temperature is about 7 degrees C.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Cumulic Endoaquolls

TYPICAL PEDON: Afton silty clay loam, on a 1 percent slopes in a cultivated field on an upland drainageway. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 15 centimeters; black (N 2/0) silty clay loam, very dark gray (N 3/0) dry; moderate fine granular structure; friable; slightly acid; abrupt wavy boundary.

A1--15 to 41 centimeters; black (N 2/0) silty clay loam, very dark gray (N 3/0) dry; moderate fine subangular blocky structure parting to moderate fine granular; friable; slightly acid; gradual smooth boundary.

A2--41 to 64 centimeters; black (10YR 2/1) silty clay loam, very dark gray (10YR 3/1) dry; moderate fine subangular blocky structure parting to moderate fine granular; friable; slightly acid; gradual smooth boundary.

A3--64 to 81 centimeters; very dark gray (10YR 3/1) silty clay loam, dark gray (10YR 4/1) dry; moderate fine subangular blocky structure parting to moderate fine granular; friable; neutral; clear smooth boundary. (Combined thickness of the A horizon is 60 to 90 centimeters.)

Bg1--81 to 94 centimeters; dark gray (5Y 4/1) silty clay loam; moderate fine subangular blocky structure; friable; many distinct very dark gray (10YR 3/1) organic coats on faces of peds; few fine prominent yellowish brown (10YR 5/6) redoximorphic concentrations; neutral; clear smooth boundary.

Bg2--94 to 109 centimeters; dark gray (5Y 4/1) silty clay loam; moderate fine subangular blocky structure; friable; many fine dark manganese concretions; common fine prominent strong brown (7.5YR 5/6) redoximorphic concentrations; neutral; abrupt wavy boundary. (Combined thickness of the Bg horizon is 20 to 50 centimeters.)

2Cg1--109 to 137 centimeters; gray (5Y 5/1) clay loam; massive; friable; many fine dark manganese concretions; common to many medium prominent strong brown (7.5YR 5/6), few fine prominent strong brown (7.5YR 5/8), and few fine and medium prominent yellowish red (5YR 4/6) redoximorphic concentrations; slightly effervescent; slightly alkaline; abrupt wavy boundary.

2Cg2--137 to 165 centimeters; gray (5Y 5/1) loam with thin strata of sandy loam and silty clay loam; massive; friable; thin strata (about 5 centimeters) of strong brown (7.5YR 5/8) medium and coarse sand at 160 to 165 centimeters (lag line); few medium prominent strong brown (7.5YR 5/6) redoximorphic concentrations; slightly effervescent; moderately alkaline; abrupt wavy boundary.

2Cg3--165 to 183 centimeters; olive gray (5Y 5/2) loam; massive; friable; few fine dark manganese concretions; few medium prominent strong brown (7.5YR 5/8) redoximorphic concentrations; about 3 percent gravel and about 2 percent fine shale fragments; slightly effervescent; moderately alkaline; abrupt wavy boundary.

2Cg4--183 to 200 centimeters; olive gray (5Y 5/2) loam; massive; firm; many fine and medium prominent strong brown (7.5YR 5/8) redoximorphic concentrations; about 3 percent gravel and about 2 percent fine shale fragments; slightly effervescent; slightly alkaline.

TYPE LOCATION: Major Land Resource Area (MLRA) 107A-Iowa and Minnesota Loess Hills; Clay County, Iowa subset; about 3 miles north of Royal; located about 500 feet north and 75 feet east of the southwest corner of section 24, T. 96 N., R. 38 W; USGS Royal topographic quadrangle; lat. 43 degrees 06 minutes 50 seconds N. and long. 95 degrees 17 minutes 21 seconds W., NAD 83.

RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon--60 to 90 centimeters
Depth to carbonates--90 to 140 centimeters
Depth to till--100 to more than 200 centimeters
Clay content in the particle-size control section (weighted average)--27 to 35 percent
Sand content in the particle-size control section (weighted average)--less than 10 percent

Ap or A horizon:
Hue--10YR or is neutral
Value--2 or 3
Chroma--0 or 1
Texture--silty clay loam
Clay content--27 to 38 percent
Sand content--less than 15 percent
Reaction--moderately acid to slightly alkaline
Calcium carbonate equivalent-0 to 10 percent

Some pedons have overwash material on the surface that includes chroma of 2

Some pedons have an AB horizon

Bg horizon:
Hue--2.5Y or 5Y
Value--3 to 5
Chroma--0 to 2
Texture--silty clay loam or silt loam
Clay content--25 to 38 percent
Sand content--less than 20 percent
Reaction--neutral to moderately alkaline
Calcium carbonate equivalent-0 to 30 percent

BCg and/ or Cg horizon (if present):
Hue--2.5Y or 5Y
Value--4 or 5
Chroma--1 to 4
Texture--silty clay loam or silt loam
Clay content--25 to 35 percent
Sand content--less than 20 percent
Reaction--neutral to moderately alkaline
Calcium carbonate equivalent-0 to 30 percent

2Cg horizon:
Hue--2.5Y or 5Y
Value--4 to 6
Chroma--1 or 2
Texture--loam or clay loam
Clay content--18 to 28 percent
Sand content--25 to 50 percent
Rock fragment content--0 to 10 percent
Reaction--slightly alkaline or moderately alkaline
Calcium carbonate equivalent-5 to 30 percent

COMPETING SERIES: These are the Catherine, Clementine, Colo, Humansville, Otter, Pastolla, Sawmill, and Whitewood series.
Catherine--are in areas with a mean annual precipitation range from 279 to 584 millimeters and are frequently saturated between depths of 0.5 and 1.2 meters when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Clementine--have carbonates at depths between 30 and 100 centimeters and are in areas with a mean annual precipitation range of 200 to 250 millimeters
Colo--have a mollic epipedon more than 90 centimeters thick
Humansville--are in areas with a mean annual air temperature range of 12 to 14 degrees C and have more clay and less sand in the lower third of the series control section (see remarks)
Otter--have a clay content that averages 18 to 27 percent in the particle-size control section
Pastolla--contain between 8 and 30 percent organic matter in the upper third of the series control section
Sawmill--are in areas with a mean annual air temperature range of 7 to 14 degrees C and a mean annual precipitation range of 760 to 1,140 millimeters, are more acid in the middle part and lower part of the series control section and do not have carbonates within a depth of 122 centimeters (see remarks)
Whitewood--are in areas with a mean annual air temperature range of 9 to 11 degrees C and a mean annual precipitation range of 500 to 660 millimeters, have a mollic epipedon 60 to more than 150 centimeters thick and have carbonates within depths of 75 to 130 centimeters or more (see remarks)

GEOGRAPHIC SETTING:
Parent material--100 to more than 200 centimeters of loess and local alluvium and the underlying till
Landform--nearly level upland drainageways on nearly level to moderately sloping, loess-mantled dissected till plains of early Wisconsin age
Slope--0 to 2 percent
Elevation--340 to 575 meters above sea level
Mean annual air temperature--6 to 9 degrees C
Mean annual precipitation--485 to 790 millimeters
Frost-free period--155 to 175 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Annieville, Gillett Grove, McCreath, Ransom, and Sac soils.
Annieville--are on higher convex landscape positions and are moderately well drained
Gillett Grove--are on slightly higher landscape positions and have mollic epipedons that are less than 60 centimeters thick
McCreath--are on slightly higher landscape positions and are frequently saturated at depths between 0.3 and 1 meter when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Ransom--are on slightly higher landscape positions and have carbonates within depths of 50 to 100 centimeters
Sac--are on higher landscape positions on convex side slopes and are frequently saturated at depths between 0.75 and 1 meter when precipitation is within one standard deviation of the 30 year mean of annual precipitation

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--poorly drained--a frequently saturated zone occurs at the surface to within 0.3 meter of the surface when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Saturated hydraulic conductivity--0.1 to 1.0 micrometers per second (moderately low)
Flooding--occasionally flooded for very brief duration from concentrated flow from adjacent higher lying soils

USE AND VEGETATION:
Some areas of these soils are in grassed waterways, but most areas are cultivated. The principal crops are corn, soybeans, small grains, and hay. The native vegetative cover is a herbaceous wetland community commonly inhabited with Bluejoint Grasses, Fowl Bluegrasses, Green Muhlies, Fox Sedges, Field Sedges, Dudleys Rushes, Torreys Rushes, Swamp Milkweeds, False Sneezeweeds, False Asters, New England Asters, White Panicled Asters, and Wild Mints.

DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Western lake section and Dissected till plains
MLRAs--Loess Uplands (102C) and Iowa and Minnesota Loess Hills (107A)
LRR M; northwestern Iowa and southwestern Minnesota
Extent--moderate

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

SERIES ESTABLISHED: Cherokee County, Iowa, 1924.

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 features recognized in this pedon include:
mollic epipedon--the zone from the surface to a depth of 81 centimeters (Ap, A1, A2 and A3 horizons);
cambic horizon--the zone from a depth of 81 to 109 centimeters (Bg1 and Bg2 horizons);
aquic moisture regime.

In MLRA 107A this soil shares limits with the Whitewood series. Additional work is needed to separate.

Differentia from Sawmill and Whitewood series needs further study and refinement.

A new pedon will be needed. The pedon used for this OSD does not fit the series pH ranges or depth to carbonates. The values for pH in the A horizon are slightly higher (8.0) than the slightly alkaline reaction class. Also, laboratory records indicate effervescence tests confirm the presence of carbonates in some parts of the A horizon.

Cation-exchange activity class is supported by lab data from KSSL

Taxonomy version--Keys to Soil Taxonomy, eleventh edition, 2010.

ADDITIONAL DATA:
Lab characterization data-(95P0226) is available from the Kellogg Soil Survey Laboratory, Lincoln Nebraska; Iowa State University: 107AIA1924IA041OSD, 1968IA161001, 1973IA119001, 1977IA141001, 1985IA143001, 1986IA093001, 1987IA035001.

National Cooperative Soil Survey
U.S.A.