LOCATION SMITHLAND IAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Aquic Cumulic Hapludolls
TYPICAL PEDON: Smithland silty clay loam, on a slope of less than 1 percent, in a cultivated field, at an elevation of 1,085 feet above sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 7 inches; very dark gray (10YR 3/1) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine granular structure; friable; few very fine roots; few very fine tubular pores; neutral; abrupt smooth boundary.
A1--7 to 16 inches; black (10YR 2/1) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure parting to weak fine granular; friable; few fine roots; few fine tubular pores; neutral; clear smooth boundary.
A2--16 to 24 inches; black (10YR 2/1) and very dark gray (10YR 3/1) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure parting to weak fine granular; friable; few fine roots; few fine tubular pores; neutral; clear smooth boundary.
A3--24 to 34 inches; very dark gray (10YR 3/1) silty clay loam; weak very fine and fine subangular blocky structure; friable; few fine roots; few fine tubular pores; few fine prominent brown (7.5YR 4/4) redoximorphic concentrations; neutral; clear wavy boundary. (Combined thickness of A horizon is 24 to 36 inches.)
Bg--34 to 40 inches; very dark gray (10YR 3/1) silty clay loam; weak very fine and fine subangular blocky structure; friable; few fine roots; few very fine tubular pores; few fine prominent yellowish brown (10YR 5/4) redoximorphic concentrations; neutral; gradual smooth boundary. (12 to 40 inches thick)
BCg--40 to 50 inches; very dark grayish brown (10YR 3/2) and dark grayish brown (10YR 4/2) silty clay loam; weak fine and medium subangular blocky structure; friable; few fine tubular pores; few fine distinct yellowish brown (10YR 5/4) and brown (7.5YR 5/4) redoximorphic concentrations; neutral; gradual smooth boundary. (0 to 12 inches thick)
Cg--50 to 60 inches; dark grayish brown (10YR 4/2) silty clay loam; massive, with weak, thin alluvial stratification; friable; few very fine tubular pores; few fine distinct yellowish brown (10YR 5/4) and common brown (7.5YR 4/4) redoximorphic concentrations; neutral.
TYPE LOCATION: Monona County, Iowa; about 95 feet west and 95 feet north of the southeast corner of sec. 5, T. 84 N., R. 43 W.; USGS Mapleton SE quadrangle; lat. 42 degrees 6 minutes 39 seconds N. and long. 95 degrees 52 minutes 1 second W., NAD 27
RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon--greater than 36 inches
Depth to carbonates--greater than 60 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 15 percent fine sand and sand coarser than fine sand
Ap and A horizons:
Hue--10YR or is neutral
Value--2 or 3
Chroma--0 to 2
Texture--silty clay loam
Clay content--27 to 40 percent
Sand content--1 to 15 percent sand
Reaction--moderately acid to neutral
Overwash phase (if it occurs):
Hue--10YR or is neutral
Value--2 or 3
Chroma--0 to 2
Texture--silt loam
Clay content--15 to 27 percent
Sand content--15 to 30 percent
Reaction--moderately acid to neutral
Thickness--6 to 15 inches
Some pedons have an AC horizon
Bg horizon:
Hue--10YR
Value--2 to 4
Chroma--1 or 2
Texture--silty clay loam
Clay content--30 to 35 percent
Sand content--1 to 15 percent
Reaction--moderately acid to neutral
BCg horizon:
Hue--10YR or 2.5Y
Value--3 or 4
Chroma--1 or 2
Texture--silty clay loam
Clay content--30 to 35 percent
Sand content--1 to 15 percent
Reaction--moderately acid to neutral
Cg horizon:
Hue--10YR or 2.5Y
Value--3 or 4
Chroma--1 or 2
Texture--silty clay loam, silt loam, or clay loam
Clay content--25 to 35 percent
Sand content--1 to 25 percent
Reaction--slightly acid or neutral
COMPETING SERIES: These are the
Ely,
Lawson, and
Littleton series.
Ely--have a mollic epipedon 24 to 36 inches thick and have a clay content of 27 to 35 percent in the particle-size control section
Lawson--do not have a cambic horizon and have a clay content of 18 to 30 percent in the series control section
Littleton--have a mollic epipedon 24 to 36 inches thick and have a clay content of 22 to 27 percent in the particle-size control section
GEOGRAPHIC SETTING:
Parent material--alluvium
Landform--flood plains and upland drainageways
Slopes--0 to 5 percent
Elevation--700 to 1,200 feet above sea level
Mean annual air temperature--46 to 55 degrees F.
Mean annual precipitation--20 to 36 inches
Frost-free period--140 to 160 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Ackmore,
Colo,
Kennebec,
Nodaway, and
Zook soils.
Ackmore--are in landform positions similar to those of the Smithland soils, have an ochric epipedon 5 to 10 inches thick, and have buried horizons
Colo--are in similar landscape positions as Smithland soils, have a clay content of 27 to 35 percent in the particle-size control section, and have a saturated zone within a depth of 1 foot during March to June in most years
Kennebec--are in the slightly higher elevations, have a mollic epipedon more than 40 inches thick, and have a saturated zone between depths of 3 to 6 feet during April to June in most years
Nodaway--are in the slightly higher elevations, have an ochric epipedon 6 to 10 inches thick, and have a saturated zone between depths of 3 to 6 feet during April to June in most years
Zook--are in the lower elevations, have a mollic epipedon more than 36 inches thick, have a clay content of 35 to 44 percent in the particle-size control section, and have a saturated zone within a depth of 1 foot during March to June in most years
DRAINAGE AND PERMEABILITY:
Drainage class--somewhat poorly drained--a saturated zone occurs between depths of 1 to 3 feet during March to June in most years and is considered apparent
Permeability--moderate
Surface runoff potential--low or very low
Flooding--rare to occasional flooding with very brief or brief duration during the months of February to November from precipitation events and snowmelt
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains and hay. A few areas are in permanent pasture with widely spaced willow and cottonwood trees. The native vegetation is big bluestem, indiangrass, switchgrass, and other grasses of the tall grass prairie.
DISTRIBUTION AND EXTENT:
LRR M, MLRAs 102B and 107; western Iowa and possibly eastern Nebraska and northwestern Missouri. This series is of moderate extent.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Monona County, Iowa, 1995.
REMARKS:
Particle-size control section--the zone from a depth of 10 to 40 inches (A1, A2, A3, and Bg horizons);
series control section--the zone from the surface to a depth of 60 inches (Ap, A1, A2, A3, Bg, BCg, and Cg horizons).
Diagnostic horizons and features recognized in this pedon:
mollic epipedon--the zone from the surface to a depth of 50 inches (Ap, A1, A2, A3, Bg, and BCg horizons);
cambic horizonthe zone from a depth of 34 to 50 inches (Bg and BCg horizons);
udic moisture regime.
Few to common, high chroma redoximorphic concentrations are at depths below 24 inches.
Cation-exchange class is inferred from lab data for similar soils in the surrounding area.
Taxonomy version--second edition, 1999.
These soils have been placed in the Colo series in previous surveys.
ADDITIONAL DATA:
Laboratory data--Iowa State University Experiment Station, Ames Iowa, File No. 56335-56342 and pedon number 00-IA193-012A
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska pedon S98IA-047-001L (http://ssldata.sc.egov.usda.gov/)