LOCATION HEDRICK IAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Mollic Oxyaquic Hapludalfs
TYPICAL PEDON: Hedrick silt loam, on convex slope of 7 percent, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 centimeters; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; weak fine granular structure; friable; common fine roots; common gray (10YR 5/1) patches and gray (10YR 6/1) dry silt coats on faces of peds in the lower 8 centimeters; neutral; clear smooth boundary. (13 to 20 centimeters thick)
Bt1--20 to 38 centimeters; brown (10YR 4/3) silty clay loam; moderate very fine angular blocky structure; friable; common fine roots; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; few distinct light gray (10YR 7/1) silt coats on faces of peds; common distinct very dark grayish brown (10YR 3/2) and dark brown (10YR 3/3) organic coats on faces of peds; neutral; clear smooth boundary.
Bt2--38 to 58 centimeters; brown (10YR 5/3), gray (10YR 6/1), and strong brown (7.5YR 5/6) silty clay loam; moderate fine angular blocky structure; friable; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; common distinct light gray (10YR 7/1) silt coats on faces of peds; moderately acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 25 to 50 centimeters.)
Btg1--58 to 81 centimeters; light brownish gray (2.5Y 6/2) silty clay loam; moderate medium subangular blocky structure; firm; common distinct brown (10YR 4/3) clay films on faces of peds; common prominent black (10YR 2/1) organic stains on surfaces along root channels; common medium prominent strong brown (7.5YR 5/6) redoximorphic concentrations; moderately acid; gradual smooth boundary.
Btg2--81 to 135 centimeters; light olive gray (5Y 6/2) silty clay loam; weak coarse prismatic structure parting to weak coarse angular blocky; firm; many prominent dark grayish brown (10YR 4/2) clay films on faces of peds; few prominent black (10YR 2/1) clay flows on surfaces along root channels; many coarse prominent strong brown (7.5YR 5/6) redoximorphic concentrations; slightly acid; gradual smooth boundary. (Combined thickness of the Btg horizon is 35 to 90 centimeters.)
BCg--135 to 160 centimeters; light olive gray (5Y 6/2) silty clay loam; weak coarse prismatic structure; firm; common dark clay flows and organic flows on surfaces along root channels; common medium prominent strong brown (7.5YR 5/6) redoximorphic concentrations; neutral; diffuse smooth boundary. (20 to 40 centimeters thick)
Cg--160 to 203 centimeters; light brownish gray (2.5Y 6/2) silt loam; massive; friable; few dark organic flows on surfaces along root channels; common coarse prominent strong brown (7.5YR 5/8) redoximorphic concentrations; moderately alkaline.
TYPE LOCATION: Major Land Resource Area (MLRA) 108C-Illinois and Iowa Deep Loess and Drift, West Central Part; Mahaska County, Iowa subset; about 2 miles south and 10 miles west of New Sharon; located about 570 feet north and 2,200 feet east of southwest corner of section 30, T. 77 N., R. 17 W.; USGS Peoria quadrangle; lat. 41 degrees 26 minutes 16 seconds N. and long. 92 degrees 51 minutes 48 seconds W., NAD83.
RANGE IN CHARACTERISTICS:
Depth to carbonates--more than 150 centimeters
Depth to redoximorphic depletions--30 to 50 centimeters
Clay content in the particle-size control section (weighted average)--30 to 35 percent
Sand content in 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--silt loam or silty clay loam
Clay content--20 to 30 percent
Sand content--less than 5 percent
Reaction--moderately acid to neutral
E horizon (where present):
Hue--10YR
Value--4 or 5
Chroma--2
Texture--silt loam or silty clay loam
Clay content--20 to 30 percent
Sand content--less than 5 percent
Reaction--strongly acid to neutral
Thickness--0 to 15 centimeters
In cultivated areas the E horizon is partially or completely mixed into the Ap horizon
Bt horizon:
Hue--10YR
Value--4 to 6
Chroma--1 to 6
Texture--silty clay loam
Clay content--32 to 37 percent
Sand content--less than 5 percent
Reaction--strongly acid to neutral
Btg horizon:
Hue--10YR to 5Y
Value--5 or 6
Chroma--1 or 2
Texture--silty clay loam
Clay content--30 to 35 percent
Sand content--less than 5 percent
Reaction--strongly acid to slightly acid
BCg or Cg horizon:
Hue--10YR to 5Y
Value--5 or 6
Chroma--1 or 2
Texture--silty clay loam or silt loam
Clay content--25 to 34 percent
Sand content--5 to 10 percent
Reaction--slightly acid to moderately alkaline
In some areas, especially on the lower parts of the landscape, a gray or grayish, loamy or clayey paleosol may be present at depths of 1.6 to 2.4 meters or more
COMPETING SERIES: These are the
Barony,
Downsouth,
Grays,
Juda,
Kaneville,
Newvienna,
Richview,
Throckmorton,
Vasa,
Windere, and
Wingate series.
Barony--have a sand content of more than 15 percent within a depth of 100 centimeters
Downsouth--are in areas that have a mean annual air temperature range of 12 to 14 degrees C and a mean annual precipitation range of 910 to 1,020 millimeters
Grays--have carbonates within a depth of 100 centimeters
Juda--have carbonates within a depth of 102 centimeters and have a clay content of 29 to 40 percent in the lower third of the series control section
Kaneville--have a sand content of more than 10 percent within a depth of 152 centimeters
Newvienna--have a clay content of 15 to 25 percent in the lower third of the series control section
Richview--have a sand content of more than 15 percent in the lower third of the series control section
Throckmorton--have carbonates within a depth 150 centimeters and have a sand content of more than 30 percent in the lower third of the series control section
Vasa--have a clay content that averages 20 to 28 percent in the particle-size control section
Windere--have a sand content of more than 15 percent within a depth of 100 centimeters, have carbonates within a depth of 150 centimeters, and have a rock fragment content of 2 to 15 percent in the lower two thirds of the series control section
Wingate--have a clay content of 15 to 27 percent, a sand content of 25 to 50 percent, and a rock fragment content of 1 to 10 percent in the lower third of the series control section
GEOGRAPHIC SETTING:
Parent material--loess
Landform--interfluves and side slopes on dissected till plains
Slopes--2 to 18 percent
Elevation--155 to 340 meters above sea level
Mean annual air temperature--8 to 11 degrees C
Mean annual precipitation--840 to 965 millimeters
Frost-free period--170 to 205 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Clinton,
Ladoga, and
Rinda soils.
Clinton--are at lower elevations on side slopes and have a clay content that averages 35 to 42 percent in the particle-size control section
Ladoga--are at higher elevations on interfluves and are at lower elevations on side slopes and have a clay content that averages 35 to 42 percent in the particle-size control section
Rinda--are at lower elevations on side slopes and have a clay content of 40 to 60 percent in the lower two thirds of the series control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--moderately well drained--a frequently saturation zone occurs between depths of 0.6 to 1.0 meter during the wettest period of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation, this saturation is considered apparent
Saturated hydraulic conductivity--1.00 to 10.00 micrometers per second in the loess and 0.10 to 1.00 micrometers per second in the underlying paleosol, when present
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybean, small grain, and grass-legume hay. The native vegetation is mixed big bluestem, little bluestem, switchgrass, other grasses of the tall grass prairie and deciduous trees (oak-hickory).
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic section--Dissected till plains
MLRA--Illinois and Iowa Deep Loess and Drift (108)
LRR M; southern and southeastern Iowa
Extent--moderate
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Mahaska County, Iowa, 1971.
REMARKS:
Particle-size control section--the zone from a depth of 20 to 70 centimeters;
series control section--the zone from the surface to a depth of 160 centimeters.
Diagnostic horizons and features recognized in this pedon include:
ochric epipedon--the zone from the surface to a depth of 20 centimeters (Ap horizon);
argillic horizon--the zone from a depth of 20 to 135 centimeters (Bt1, Bt2, Btg1, and Btg2 horizons);
udic moisture regime.
Cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Oxyaquic subgroup based on a zone of saturation within 100 centimeters for 20 or more consecutive days or 30 or more cumulative days in normal years.
Future investigations are needed on map units of Hedrick soils to determine if a paleosol contact is consistently encountered within the series control section.
Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.