LOCATION KOSZTA IAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Udollic Endoaqualfs
TYPICAL PEDON: Koszta silt loam, on a slope of about 1 percent, in a timbered pasture. (Colors are for moist soil unless otherwise stated.)
A--0 to 20 centimeters; very dark grayish brown (10YR 3/2) silt loam; dark grayish brown (10YR 4/2) dry; weak fine granular structure; friable; common distinct very dark brown (10YR 2/2) organic stains on faces of peds; slightly acid; abrupt smooth boundary. (13 to 23 centimeters thick)
E--20 to 33 centimeters; dark grayish brown (10YR 4/2) silt loam; weak medium platy structure parting to weak fine granular; friable; few fine distinct black (10YR 2/1) iron-manganese concretions; common fine distinct strong brown (7.5YR 4/6) iron-manganese masses; common fine faint grayish brown (10YR 5/2) redoximorphic depletions; strongly acid; clear smooth boundary. (10 to 18 centimeters thick)
BE--33 to 53 centimeters; brown (10YR 4/3) silty clay loam; moderate fine subangular blocky structure; friable; few distinct light gray (10YR 7/2) dry, silt coats on all faces of peds; few fine distinct black (10YR 2/1) iron-manganese concretions; common fine distinct strong brown (7.5YR 5/6) iron-manganese masses; common fine distinct yellowish brown (10YR 5/6) redoximorphic concentrations; common fine faint grayish brown (10YR 5/2) redoximorphic depletions; strongly acid; gradual smooth boundary. (0 to 23 centimeters thick)
Btg1--53 to 86 centimeters; grayish brown (10YR 5/2) silty clay loam; moderate medium subangular blocky structure; firm; common distinct dark grayish brown (10YR 4/2) clay films on faces of peds; few distinct light gray (10YR 7/2) dry, silt coats on faces of peds; few fine prominent black (10YR 2/1) iron-manganese concretions; common fine distinct strong brown (7.5YR 5/6) and strong brown (7.5YR 5/8) iron-manganese masses; strongly acid; gradual smooth boundary.
Btg2--86 to 122 centimeters; light brownish gray (10YR 6/2) and grayish brown (10YR 5/2) silty clay loam; weak medium subangular blocky structure; firm; common fine pores; common distinct dark grayish brown (10YR 4/2) clay films on faces of peds; common medium prominent black (10YR 2/1) iron-manganese concretions; common fine prominent strong brown (7.5YR 5/6) and strong brown (7.5YR 5/8) iron-manganese masses; moderately acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 50 to 92 centimeters.)
BCg--122 to 145 centimeters; light brownish gray (2.5Y 6/2) silty clay loam; weak medium prismatic structure; friable; common fine pores; common medium prominent black (10YR 2/1) iron-manganese concretions; common medium prominent strong brown (7.5YR 5/6) iron-manganese masses; neutral; gradual smooth boundary. (0 to 50 centimeters thick)
Cg--145 to 203 centimeters; light brownish gray (2.5Y 6/2) silt loam; massive; friable; common fine pores; common medium prominent black (10YR 2/1) iron-manganese concretions; common fine and medium prominent strong brown (7.5YR 4/6) and strong brown (7.5YR 5/6) iron-manganese masses; neutral.
TYPE LOCATION: Major Land Resource Area (MLRA) 108C-Illinois and Iowa Deep Loess and Drift, West Central Part; Johnson County, Iowa subset; about 5 miles southwest of Iowa City; located about 2,580 feet south and 200 feet west of the northeast corner of section 34, T. 79 N., R. 7 W; USGS Williamstown topographic quadrangle; lat. 41 degrees 36 minutes 24 seconds N. and long. 91 degrees 38 minutes 21 seconds W, NAD 83.
RANGE IN CHARACTERISTICS:
Depth to carbonates--more than 178 centimeters
Clay content of the particle-size control section (weighted average)--27 to 35 percent
Sand content of the particle-size control section (weighted average)--less than 15 percent
Ap or A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--silt loam
Clay content--20 to 27 percent
Sand content--less than 15 percent
Reaction--moderately acid to neutral
E horizon:
Hue--10YR
Value--4 or 5
Chroma--2
Texture--silt loam
Clay content--18 to 25 percent
Sand content--less than 15 percent
Reaction--strongly acid to slightly acid
BE horizon (when present):
Hue--10YR
Value--4
Chroma--2 or 3
Texture--silty clay loam
Clay content--27 to 35 percent
Sand content--less than 15 percent
Reaction--strongly acid to slightly acid
Some horizon between the base of the A or Ap horizon and a depth of 75 centimeters has chroma greater than 2 in 40 percent or more of the matrix
Btg horizon:
Hue--10YR
Value--4 or 5
Chroma--2
Texture--silty clay loam
Clay content--28 to 35 percent
Sand content--less than 15 percent
Reaction--strongly acid to slightly acid
BCg horizon (when present):
Hue--10YR or 2.5Y
Value--4 to 6
Chroma--2 to 6
Texture--silty clay loam
Clay content--27 to 33 percent
Sand content--less than 15 percent
Reaction--moderately acid to neutral
C or Cg horizon:
Hue--10YR or 2.5Y
Value--4 to 6
Chroma--2 to 6
Texture--silty clay loam or silt loam, but thin strata of coarser textures are within the range
Clay content--25 to 33 percent
Sand content--less than 15 percent
Reaction--moderately acid to neutral
COMPETING SERIES: These are the
Atterberry,
Bethalto,
Canoe,
Curran,
Emery,
Franklin,
Millbrook,
Mulvey,
Virgil, and
Wauconda series.
Atterberry--have a clay content of less than 27 percent in the lower quarter of the series control section
Bethalto--have a clay content of 18 to 27 percent in the lower third of the series control section
Canoe--have a clay content that averages 20 to 28 percent in the particle-size control section
Curran--have a sand content of more than 70 percent in the lower third of the series control section
Emery--have a clay content of 18 to 35 percent and a sand content of 8 to 25 percent in the lower third of the series control section
Franklin--have a sand content of 35 to 50 percent in the lower third of the series control section
Millbrook--have a sand content of 20 to 70 percent in the lower third of the series control section
Mulvey--have a sand content of 50 to 75 percent in the lower third of the series control section
Virgil--have a sand content of 20 to 80 percent in the lower third of the series control section
Wauconda--have carbonates within a depth of 100 centimeters
GEOGRAPHIC SETTING:
Parent material--silty alluvium
Landform--low stream terraces
Slope--0 to 3 percent
Elevation--183 to 396 meters above sea level
Mean annual temperature--8 to 11 degrees C
Mean annual precipitation--750 to 870 millimeters
Frost-free period--165 to 180 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Amana,
Coppock,
Tuskeego, and
Watkins soils.
Amana--are at lower landscape positions on floodplains and have a mollic epipedon 25 to 60 centimeters thick
Coppock--are at slightly higher landscape positions on stream terraces, foot slopes, and alluvial fans and have albic horizons that are 36 to 61 centimeters thick
Tuskeego--are on landscape positions similar to those of the Koszta soils and have a clay content that averages 35 to 45 percent in the particle-size control section
Watkins--are on landscape positions similar to those of the Koszta soils and do not have a frequently saturated zone within a depth of 1.8 meters during the wettest periods of normal years
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs at a depth of 0.3 meter during the wettest periods of normal years
Saturated hydraulic conductivity--4.23 to 14.11 micrometers per second (moderately high)
Surface runoff potential--negligible to low
Flooding--rarely flooded for brief duration
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, and legume hays. Some areas are forested or pastured. The native vegetation is mixed big bluestem, little bluestem, switchgrass, other grasses of the tall grass prairie and deciduous trees.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic section--Dissected till plains
MLRAs--Illinois and Iowa Deep Loess and Drift (108) and Iowa and Missouri Heavy Till Plain (109)
LRR M--southern and eastern Iowa
Extent--small
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Iowa County, Iowa, 1965.
REMARKS:
Particle-size control section--the zone from a depth of 53 to 103 centimeters;
series control section--the zone from the surface to a depth of 150 centimeters.
Diagnostic horizons and features recognized in this pedon include:
ochric epipedon--the zone from the surface to a depth of 33 centimeters (Ap and E horizons);
albic horizon--the zone from 20 to 33 centimeters (E horizon);
argillic horizon--the zone from a depth of 53 to 122 centimeters (Btg1 and Btg2 horizons);
aquic moisture regime.
Aqualfs suborder based on morphology of typical pedon.
Cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.