LOCATION IRWIN KS

Established Series
Rev. JMA, CEW, BKN
07/2020

IRWIN SERIES

The Irwin series consists of deep and very deep, moderately well drained that formed in loess over colluvium over residuum weathered from shale. Irwin soils are on hillslopes on uplands in the Central Kansas Sandstone Hills (MLRA 74). Slopes range from 0 to 8 percent. Mean annual precipitation is 840 millimeters (33 inches) and Mean annual air temperature is 12 degrees C (54 degrees F), at the type location.

TAXONOMIC CLASS: Fine, mixed, superactive, mesic Pachic Argiustolls

TYPICAL PEDON: Irwin silty clay loam - on a northwest-facing, convex, 3 percent slope backslope in rangeland at an elevation of 408 meters (1338 feet). (Colors are for dry soil unless otherwise stated.) As described on September 6, 1988.

A--0 to 15 centimeters (0 to 6 inches); very dark gray (10YR 3/1) silty clay loam, very dark brown (10YR 2/2) moist; 3 percent sand; 28 percent clay; moderate fine granular structure; hard, friable, slightly plastic and slightly sticky; many fine and medium roots throughout; few distinct gray (10YR 5/1) discontinuous sand or silt coats on faces of peds; moderately acid; clear smooth boundary (12 to 33 centimeters thick (5 to 13 inches).) Lab sample # KSUSS2480

BA--15 to 33 centimeters (6 to 13 inches); very dark grayish brown (10YR 3/2) silty clay loam, very dark brown (10YR 2/2) moist; 3 percent sand; 30 percent clay; moderate medium subangular blocky structure; hard, firm, plastic and sticky; many fine roots throughout; few distinct gray (10YR 5/1) discontinuous sand or silt coats on faces of peds; moderately acid; abrupt smooth boundary. (0 to 25 centimeters (0 to 10 inches).) Lab sample # KSUSS2481

Bt1--33 to 58 centimeters (13 to 23 inches); dark grayish brown (10YR 4/2) silty clay, very dark brown (10YR 2/2) and very dark grayish brown (10YR 3/2) crushed moist; 2 percent sand; 46 percent clay; strong medium subangular blocky structure; very hard, very firm, very plastic and very sticky; common very fine and fine roots throughout; few faint very dark brown (10YR 2/2) continuous clay films on faces of peds; moderately acid; gradual smooth boundary. Lab sample # KSUSS2482

Bt2--58 to 76 centimeters (23 to 30 inches); brown (10YR 4/3) silty clay, dark brown (10YR 3/3) moist; 2 percent sand; 42 percent clay; moderate medium blocky structure; extremely hard, extremely firm, very plastic and very sticky; common very fine roots between peds; few faint very dark grayish brown (10YR 3/2) discontinuous clay films on faces of peds; slightly acid; gradual smooth boundary (Combined thickness of the Bt horizons is 38 to 100 centimeters (15 to 39 inches).) Lab sample # KSUSS2483

Btk--76 to 104 centimeters (30 to 41 inches); brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; 4 percent sand; 36 percent clay; weak medium blocky structure; very hard, very firm, very plastic and very sticky; few very fine roots throughout; very few faint discontinuous clay films on faces of peds; common fine and medium rounded lime concretions; slightly alkaline; gradual smooth boundary. (0 to 33 centimeters (0 to 13 inches).) Lab sample # KSUSS2484

2Bt1--104 to 137 centimeters (41 to 54 inches); brown (7.5YR 5/4) silty clay loam, brown to brown (7.5YR 4/4) moist; 2 percent sand; 34 percent clay; moderate medium subangular blocky structure; hard, firm, plastic and sticky; very few discontinuous clay films on faces of peds; common fine irregular masses of oxidized iron and common fine spherical manganese masses throughout; slightly alkaline; clear smooth boundary. Lab sample # KSUSS2485

2Bt2--137 to 193 centimeters (54 to 76 inches); 70 percent brown (7.5YR 4/4), with 30 percent brown (10YR 5/3) silty clay loam; 70 percent dark brown (7.5YR 3/4), with 20 percent brown to brown (10YR 4/3), and 10 percent dark grayish brown (10YR 4/2) moist; 2 percent sand; 38 percent clay; weak fine subangular blocky structure; hard, firm, plastic and sticky; very few faint discontinuous clay films on faces of peds; common fine irregular masses of oxidized iron and common fine spherical manganese masses throughout; 1 percent limestone pebbles; slightly alkaline; gradual smooth boundary. (Combined thickness of the 2Bt horizons is 0 to 89 centimeters (0 to 35 inches).) Lab sample # KSUSS2486

3BC--193 to 200 centimeters (76 to 80 inches);gravely silty clay loam, dark brown (7.5YR 3/4), moist; 1 percent sand; 32 percent clay; weak fine subangular blocky structure; firm, hard when dry; 25 percent subangular 2- to 75 -millimeter noncalcareous shale fragments; neutral; Lab sample # KSUSS2487

TYPE LOCATION: Geary County, Kansas; about 16 kilometers (10 miles) south of Junction City; located about 713 meters (2,340 feet) east and 98 meters (320 feet) north of the southwest corner of section 25, T. 13 S., R. 5 E. (Public Land Survey location); Wreford, Kansas USGS topographic quadrangle; latitude 38 degrees, 53 minutes, 6 seconds N; longitude 96 degrees, 49 minutes, 33 seconds W, WGS84.

RANGE IN CHARACTERISTICS:
Soil moisture regime: ustic bordering on udic
Soil temperature regime: mesic
Thickness of the mollic epipedon: 50 to 100 centimeters (20 to 40 inches)
Thickness of the argillic horizon: 70 to 180 centimeters (28 to 71 inches)
Depth to a subhorizon containing more than 40 percent clay: 23 to 35 centimeters (9 to 14 inches)
Depth to secondary calcium carbonate: greater than 60 centimeters (24 inches).
Depth to redox concentrations: usually greater than 102 centimeters (30 inches)
Depth to redox depletions: greater than 102 centimeters (40 inches)
Depth to bedrock: 100 centimeters to more than 150 centimeters (40 to more than 60 inches)
Soil moisture: The soil moisture control section is intermittently moist in some part from March through October; driest in November through February Mean annual soil temperature: 12 to 14 degrees C (53 to 58 degrees F)
Particle size control section (weighted average):
Clay content: 35 to 55 percent
Sand content: 1 to 20 percent

A or BA horizon:
Hue: 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 1 to 3 dry or moist
Texture: silty clay loam
Clay content: 28 to 39 percent
Sand content: 1 to 20 percent
Reaction: moderately acid to neutral.
Sodium Adsorption Ratio: 0 to 1.

Bt horizon:
Hue: 10YR or 7.5YR
Value: 4 to 6 dry, 2 to 4 moist
Chroma: 2 or 3 dry or moist
Texture: silty clay, silty clay loam, or clay
Clay content: 35 to 60 percent
Sand content: 1 to 20 percent
Reaction: moderately acid to slightly alkaline.
Sodium Adsorption Ratio: 0 to 5.

Btk horizon:
Hue: 10YR or 7.5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 to 4 dry or moist
Texture: silty clay, clay, or silty clay loam
Clay content: 35 to 55 percent
Sand content: 1 to 20 percent
Calcium carbonate equivalent: 1 to 5 percent.
Reaction: neutral to moderately alkaline.
Sodium Adsorption Ratio: 0 to 7.

2Bt or 2Btk horizon:
Hue: 7.5YR or 10YR
Value: 4 to 6 dry, 3 or 4 moist
Chroma: 2 to 4 dry or moist
Texture: silty clay, clay, or silty clay loam
Clay content: 35 to 60 percent
Sand content: 1 to 20 percent
Rock Fragments: 0 to 2 percent, limestone or shale channers
Calcium carbonate equivalent: 0 to 10 percent.
Reaction: slightly acid to moderately alkaline.
Sodium Adsorption Ratio: 0 to 9.

2C, 2BC, 3C or 3BC horizon:
Hue: 2.5Y to 5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 to 5 dry or moist
Texture: silty clay, clay, or silty clay loam or their channery counterparts.
Clay content: 30 to 55 percent
Sand content: 1 to 20 percent
Rock fragments: 0 to 30 percent, limestone or shale channers
Reaction: neutral to moderately alkaline.
Sodium Adsorption Ratio: 0 to 9.

Some profiles have 2Cr horizon from weathered shale that has similar properties to the 2C horizon.

COMPETING SERIES: These are the Conchovar, Knifehill, Lubbock, Millpaw,
Nutreeah, Ruidoso, and Tully series.
Conchovar soils have redoximorphic features occurring between 50 and 100 centimeters (20 to 40 inches) (somewhat poorly drained).
Knifehill, Lubbock, Millpaw and Ruidoso soils are drier in the soil moisture control section during May to July.
Nutreeah soils have an accumulation of salts between 50 to 89 centimeters (20 to 35 inches).
Tully soils do not have horizons within 35 centimeters (14 inches) that have more than 40 percent clay.

GEOGRAPHIC SETTING:
Parent material: loess over colluvium over residuum from weathered shale
Landform: hillslopes of uplands
Slopes: 0 to 8 percent
Elevation: 300 to 505 meters (980 to 1660 feet)
Mean annual air temperature: 12 to 14 degrees C (54 to 58 degrees F)
Mean annual precipitation: 790 to 1060 millimeters (31 to 42 inches)
Precipitation pattern: Precipitation is usually evenly distributed throughout the year with the exception of November through February being the driest months and May and June being the wettest months. Summer precipitation occurs during intense summer thunderstorms.
Frost-free period: 160 to 200 days

GEOGRAPHICALLY ASSOCIATED SOILS:
These are the Dwight, Konza, Labette, and Ladysmith soils.
The Labette soils have shale and limestone respectively occurring within 100 centimeters (40 inches) and occur lower on the slopes.
The Dwight soils have an accumulation of salts in the control section and occur on summits of hillslopes.
The Konza soils are less than 23 centimeters (9 inches) to horizons containing more than 40 percent clay, contain higher amounts of salts, and are on similar landscape positions.
The Ladysmith soils have redoximorphic features occurring between 50 and 100 centimeters (20 to 40 inches) (somewhat poorly drained) and occur on summits of hillslopes.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage: moderately well
Runoff: high or very high
Saturated hydraulic conductivity: low

USE AND VEGETATION:
About half is cultivated; wheat and sorghum are the principal crops. The remainder is used as rangeland. Native vegetation is mid or tall grass prairie.

DISTRIBUTION AND EXTENT: East central Kansas; Land Resource Region H, Central Great Plains Winter Wheat and Range; MLRA 74 Central Kansas Sandstone Hills; MLRA 76 Bluestem Hills; Land Resource Region M, Central Feed Grains and Livestock; MLRA 112 Cherokee Prairies. The series is of large extent. Estimated acreage is more than one million acres.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Salina, Kansas

SERIES ESTABLISHED: Geary County, Kansas, 1958.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 33 to 83 centimeters (13 to 33 inches). (Bt1, Bt2, Btk horizons)
Mollic epipedon: The zone from 0 to 76 centimeters (0 to 30 inches). (A, BA, Bt1 and Bt2 horizons)
Argillic horizon: The zone from 33 to 193 centimeters (13 to 76 inches). (Bt1, Bt2, Btk, 2Bt1, and 2Bt2 horizons)
Secondary carbonates: the zone from 76 to 104 centimeters (30 to 41 inches) (Btk horizon).
Redoximorphic features: 104 to 193 centimeters (41 to 76 inches) (2Bt1 and 2Bt2 horizons).

07/2003 WAW CEC activity class added, change to semi-tabular format. Added additional competing series

12/2010 GLP Added MLRA to opening paragraph, updated parent material and landform, converted English measurements to metric, added percent sand and clay to horizon and range in characteristics, and added lab sample numbers to horizon descriptions. Changed texture classes and reaction classes to match lab data. Extended the depth of the type location to 200 centimeters using the original description that went down to 200 centimeters in which we added a 3BC horizon that was described. In the Range in Characteristics, added soil moisture, mean annual soil temperature, particle size clay and sand percents, Added Btk and 2Bt, 2Btk horizon data to the Range in Characteristics. Added clay and sand percents in the RIC horizon data and added rock fragments and calcium carbonate equivalent where needed. Updated competing series section. Updated Geographic settings section. Updated Geographically Associated Soils section.
Updated Drainage and Permeability section to Drainage and Saturated Hydraulic Conductivity.
Updated Distribution and Extent section. Added additional data for typical pedon.

4/2017 BKN Updated parent material. Added on a northwest-facing, convex, 3 percent slope backslope in rangeland at an elevation of 408 meters (1338 feet) to typical pedon. Added redox features to horizon descriptions for 2Bt1 and 2Bt2 horizons. Added depth to redox features to RIC and remarks. Added SAR range to RIC. Added Konza as a geographically associated soil.

Keys to Soil Taxonomy: Twelfth Edition, 2014.

ADDITIONAL DATA:
Data for typical pedon is from Kansas State University Characterization Laboratory, Manhattan, Kansas; pedon samples 2480-2487 (88KS061004). Additional laboratory data- National Soil Survey Laboratory, Lincoln, Nebraska samples 87P0011 (86KS015001); 90P0510 (90KS061002), 05N0660 (05KS061001); Kansas State University Soil Characterization Laboratory samples 2423-2429, pedon 01KS197003.
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National Cooperative Soil Survey
U.S.A.