LOCATION MAHASKA IA
Established Series
Rev. FFR-JAL-RPD
12/2013
MAHASKA SERIES
The Mahaska series consists of very deep, somewhat poorly drained soils formed in loess. These soils are on summits of interfluves on dissected till plains and on treads and risers on stream terraces. Slopes range from 0 to 5 percent. Mean annual air temperature is about 11 degrees C (51 degrees F). Mean annual precipitation is about 81 centimeters (32 inches).
TAXONOMIC CLASS: Fine, smectitic, mesic Aquertic Argiudolls
TYPICAL PEDON: Mahaska silty clay loam, on a southeast-facing, convex ridgetop with a slope of about 1 percent, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 18 centimeters (0 to 7 inches); black (10YR 2/1) silty clay loam, dark gray (10YR 4/1) dry; moderate fine subangular blocky and moderate fine angular blocky structure; friable; few fine roots; few fine tubular pores; slightly acid; abrupt smooth boundary.
A1--18 to 33 centimeters (7 to 13 inches); black (10YR 2/1) silty clay loam, dark gray (10YR 4/1) dry; moderate fine subangular blocky structure parting to moderate fine granular; friable; few fine roots; few fine tubular pores; slightly acid; clear smooth boundary.
A2--33 to 46 centimeters (13 to 18 inches); very dark gray (10YR 3/1) silty clay loam, dark gray (10YR 4/1) dry; moderate fine subangular blocky structure; friable; few fine roots; few fine tubular pores; few fine irregular masses of iron-manganese; slightly acid; gradual smooth boundary. [Combined thickness of the A horizon is 36 to 50 centimeters (14 to 20 inches).]
BA--46 to 61 centimeters (18 to 24 inches); dark grayish brown (2.5Y 4/2) and olive brown (2.5Y 4/4) silty clay loam, very dark grayish brown (10YR 3/2) kneaded, gray (10YR 5/1) dry; weak medium prismatic structure parting to moderate very fine and fine subangular blocky; friable; few fine roots; few fine tubular pores; many distinct very dark gray (10YR 3/1) organic coats on faces of peds; few fine irregular masses of iron-manganese; moderately acid; gradual smooth boundary. [10 to 15 centimeters (4 to 6 inches) thick]
Bt--61 to 76 centimeters (24 to 30 inches); light olive brown (2.5Y 5/3) silty clay; weak fine prismatic structure parting to moderate fine subangular blocky; firm; few fine roots; few fine tubular pores; common distinct dark gray (10YR 4/1) and dark grayish brown (10YR 4/2) clay films on faces of peds; very few distinct very dark gray (10YR 3/1) organic coats on faces of peds; common fine prominent yellowish brown (10YR 5/8) redoximorphic concentrations; common fine faint grayish brown (2.5Y 5/2) redoximorphic depletions; few fine irregular masses of iron-manganese; moderately acid; gradual smooth boundary.
Btg1--76 to 102 centimeters (30 to 40 inches); grayish brown (2.5Y 5/2) silty clay loam; moderate medium prismatic structure parting to moderate medium subangular blocky; firm; few fine roots; few fine tubular pores; many distinct dark grayish brown (10YR 4/2) clay films on faces of peds; common fine prominent yellowish brown (10YR 5/6) and brown (7.5YR 4/4) redoximorphic concentrations; few fine irregular masses of iron-manganese; moderately acid; gradual smooth boundary.
Btg2--102 to 130 centimeters (40 to 51 inches); light olive gray (5Y 6/2) silty clay loam; weak medium prismatic structure; friable; few fine roots; few fine tubular pores; many distinct olive gray (5Y 5/2) clay films on faces of peds and few faint dark gray (10YR 4/1) clay films on surfaces along root channels; few distinct black (10YR 2/1) organic coats on vertical faces of peds; common fine and medium prominent yellowish brown (10YR 5/6) and few fine prominent strong brown (7.5YR 5/8) redoximorphic concentrations; few fine irregular masses of iron-manganese; neutral; gradual smooth boundary.
Btg3--130 to 155 centimeters (51 to 61 inches); olive gray (5Y 5/2) silty clay loam; weak coarse prismatic structure; friable; few fine roots; few fine tubular pores; few faint gray (5Y 5/1) clay films on surfaces along root channels; very few distinct black (10YR 2/1) organic coats on vertical faces of peds; common fine prominent yellowish brown (10YR 5/6) and few coarse prominent strong brown (7.5YR 5/8) redoximorphic concentrations; few fine irregular masses of iron-manganese; neutral; gradual smooth boundary. [Combined thickness of the Bt and Btg horizon is 76 to 127 centimeters (30 to 50 inches).]
BCg--155 to 203 centimeters (61 to 80 inches); gray (5Y 6/1) silty clay loam; extremely coarse prismatic structure dissected by few oblique fractures; friable; few fine tubular pores; very few distinct black (10YR 2/1) organic coats on vertical faces of peds; common fine prominent yellowish brown (10YR 5/6) redoximorphic concentrations; few fine irregular masses of iron-manganese; neutral.
TYPE LOCATION: Major Land Resource Area (MLRA) 108C-Illinois and Iowa Deep Loess and Drift, West Central Part; Keokuk County, Iowa subset; about 1 mile south of Kinross; about 351 meters (1,150 feet) south and 724 meters (2,375 feet) west of the northeast corner of section 34, T. 77 N., R. 10 W.; USGS Kinross quadrangle; lat. 41 degrees 26 minutes 9 seconds N. and long. 91 degrees 59 minutes 38 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Thickness of mollic epipedon--36 to 61 centimeters (14 to 24 inches)
Depth to carbonates--greater than 152 centimeters (60 inches)
Clay content of the particle-size control section (weighted average)--35 to 42 percent
Sand content of the particle-size control section (weighted average)--less than 5 percent
Rock fragment content--0 percent
Ap or A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--silty clay loam or silt loam
Clay content--20 to 32 percent
Sand content--less than 10 percent
Reaction--very strongly acid to neutral
BA horizon:
Hue--10YR or 2.5Y
Value--3 or 4
Chroma--2 to 4
Texture--silty clay loam
Clay content--27 to 37 percent
Sand content--less than 5 percent
Reaction--very strongly acid to slightly acid
Where chroma is 3 or 4, redoximorphic depletions are present
Bt and Btg horizon (upper part):
Hue--10YR or 2.5Y
Value--4 or 5
Chroma--2 or 3
Texture--silty clay or silty clay loam
Clay content--35 to 42 percent
Sand content--less than 5 percent
Reaction--very strongly acid to slightly acid
Btg (lower part) and BCg horizon:
Hue--2.5Y or 5Y
Value--4 to 6
Chroma--2 or 3
Texture--silty clay or silty clay loam
Clay content--35 to 42 percent
Sand content--less than 5 percent
Reaction--very strongly acid to neutral
Cg horizon (when present):
Hue--2.5Y or 5Y
Value--5 or 6
Chroma--1 or 2
Texture--silty clay loam or silt loam
Clay content--24 to 32 percent
Sand content--less than 5 percent
Reaction:--moderately acid to slightly alkaline
COMPETING SERIES: These are the
Arisburg,
Arispe,
Chase,
Good Thunder,
Greenton,
Grundy,
Lagonda,
Lamoni,
Martin,
Mayberry,
Seymour,
Shorewood,
Tina, and
Wymore series.
Arisburg--are in areas with a mean annual air temperature range of 12 to 14 degrees C (53 to 57 degrees F)
Arispe--have mollic epipedons 25 to 38 centimeters (10 to 15 inches) thick
Chase--have mollic epipedons greater than 91 centimeters (36 inches) thick
Good Thunder--have carbonates within depths of 71 to 127 centimeters (28 to 50 inches)
Greenton--have shale rock fragments in the lower half of the series control section
Grundy--have a clay content of 42 to 48 percent in the particle-size control section
Lagonda--have a sand content of more than 5 percent in the lower half of the series control section
Lamoni--have a sand content of more than 15 percent throughout the series control section
Martin--have mollic epipedons 61 to 91 centimeters (24 to 36 inches) thick
Mayberry--have matrix hue of 5YR or 7.5YR in the particle-size control section
Seymour--have subhorizons with a clay content of more than 42 percent in the particle-size control section
Shorewood--have carbonates within depths of 71 to 127 centimeters (28 to 50 inches) and have a rock fragment content of 2 to 8 percent sand in the lower third of the series control section
Tina--have a sand content of more than 20 percent sand in the lower third of the series control section
Wymore--have a clay content of 42 to 55 percent in the particle-size control section
GEOGRAPHIC SETTING:
Parent material--loess
Landform--summits of interfluves on dissected till plains and on treads and risers on stream terraces
Slopes--0 to 5 percent
Elevation--160 to 305 meters (525 to 1,000 feet) above sea level
Mean annual air temperature--9 to 11 degrees C (49 to 52 degrees F)
Mean annual precipitation--91 to 97 centimeters (35 to 38 inches)
Frost-free period--170 to 204 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Nira,
Otley,
Sperry, and
Taintor soils.
Nira--are at slightly lower elevations on nose slopes, have a cambic horizon, and have a clay content of less than 35 percent in the particle-size control section
Otley--are at slightly lower elevations on side slopes and have a frequently saturated zone within depths of 1.2 to 1.8 meters (4 to 6 feet) in normal years
Sperry--are in shallow depressions on interfluves, have a albic horizon, and have a frequently saturated zone within 0.3 meter (1 foot) in normal years
Taintor--are on the flatter parts of summits and have a frequently saturated zone within 0.3 meter (1 foot) in normal years
DRAINAGE AND PERMEABILITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs within depths of 0.3 to 1.1 meter (1 to 3.5 feet) sometime during April to June in normal years
Saturated hydraulic conductivity--moderately high
Surface runoff potential--negligible to low
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, and legume hay. 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--Dissected till plains
MLRA(s)--Illinois and Iowa Deep Loess and Drift (108) and Iowa and Missouri Heavy Till Plain (109)
LRR M; southeastern Iowa
Extent--large
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Jefferson County, Iowa, 1957
REMARKS:
Particle-size control section--the zone from a depth of 61 to 111 centimeters (24 to 44 inches) (Bt, Btg1, and Btg2 horizons);
series control section--the zone from the surface to a depth of 155 centimeters (0 to 61 inches) (Ap, A1, A2, BA, Bt, Btg1, Btg2, Btg3 and BCg horizons).
Diagnostic horizons and features recognized in this pedon:
mollic epipedon--from the surface to a depth of 46 centimeters (18 inches) (Ap, A1, and A2 horizons);
argillic horizon--the zone from a depth of 61 to 155 centimeters (24 to 61 inches) (Bt, Btg1, Btg2, and Btg3 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 (39 inches).
Taxonomy version--Keys to Soil Taxonomy, eleventh edition, 2010.
ADDITIONAL DATA:
Pedon data from soil characterization lab at Iowa State University and the KSSL was evaluated in December 2013 in revising the Range in Characteristics.
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska-pedon ID 61IA-107-001, 61IA183002, and 84IA0870013.
(http://ssldata.sc.egov.usda.gov/).
Laboratory data--Soil Survey Investigations Report No. 3.
National Cooperative Soil Survey
U.S.A.