LOCATION MCGIRK MOEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Chromic Vertic Endoaqualfs
TYPICAL PEDON: McGirk silt loam - on a 7 percent concave west-facing slope in a cultivated field at an elevation of 825 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 6 inches; dark grayish brown (10YR 4/2) silt loam, grayish brown (10YR 5/2) dry; weak fine granular structure; friable; many fine roots; slightly acid; abrupt smooth boundary. (4 to 12 inches thick)
BEg--6 to 11 inches; dark grayish brown (10YR 4/2) silty clay loam; weak very fine subangular blocky structure; firm; common fine roots; common fine faint brown (10YR 4/3) masses of iron accumulation throughout; strongly acid; clear smooth boundary. (0 to 6 inches thick)
Btg1--11 to 17 inches; dark grayish brown (10YR 4/2) silty clay; weak fine subangular blocky structure; very firm; common fine roots; common faint clay films on faces of peds; common fine faint brown (10YR 4/3) masses of iron accumulation and grayish brown (10YR 5/2) iron depletions throughout; very strongly acid; clear smooth boundary.
Btg2--17 to 24 inches; grayish brown (2.5Y 5/2) silty clay; weak fine subangular blocky structure; very firm; few fine roots; many faint clay films on faces of peds; few medium distinct dark yellowish brown (10YR 4/6) masses of iron accumulation throughout; very strongly acid; clear smooth boundary.
Btg3--24 to 30 inches; dark grayish brown (10YR 4/2) silty clay; moderate fine subangular blocky structure; very firm; few fine roots; many faint clay films on faces of peds; many fine prominent strong brown (7.5YR 5/6) masses of iron accumulation and common fine faint grayish brown (10YR 5/2) iron depletions throughout; strongly acid; gradual smooth boundary.
Btg4--30 to 46 inches; grayish brown (2.5Y 5/2) silty clay; moderate fine and medium subangular blocky structure; very firm; few fine roots; many faint clay films on faces of peds; many fine prominent strong brown (7.5YR 5/6) masses of iron accumulation throughout; strongly acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 30 to 70 inches.)
BCg--46 to 57 inches; gray (10YR 5/1) silty clay; weak medium subangular blocky structure; very firm; many fine prominent strong brown (7.5YR 5/6) masses of iron accumulation and common medium distinct grayish brown (2.5Y 5/2) iron depletions throughout; moderately acid; clear smooth boundary. (0 to 15 inches thick)
Cg--57 to 66 inches; gray (10YR 5/1) silty clay loam; massive; firm; many fine prominent strong brown (7.5YR 5/6) masses of iron accumulation and common medium distinct grayish brown (2.5Y 5/2) iron depletions throughout; moderately acid.
TYPE LOCATION: Jackson County, Missouri; 6 miles north of Lonejack; 1,500 feet south and 2,300 feet east of the northwest corner of section 19, T. 48 N., R. 29 W.; USGS Tarsney Lakes quadrangle; latitude 38 degrees 57 minutes 27 seconds N. and longitude 94 degrees 09 minutes 37 seconds W.
RANGE IN CHARACTERISTICS: McGirk soils average less than 5 percent sand in the particle size control section.
The Ap horizon has hue of 10YR, value of 4 or 5, and chroma of 2 or 3. Some pedons have an Eg horizon with hue of 10YR to 2.5Y, value of 6 or 7 and chroma of 2. It is silt loam. Reaction is typically slightly acid to strongly acid, but can be neutral where limed.
The BEg horizon has hue of 10YR, value of 4 to 6 and chroma of 2. Reaction is very strongly acid or strongly acid.
The Btg and 2Btg horizons have hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 1 or 2. It has masses of iron accumulation or depletions with hue of 10YR or 7.5YR, value of 4 to 6 and chroma of 2 to 8. They are silty clay loam, silty clay, or clay with 35 to 60 percent clay and 0 to 3 percent rock fragments. Reaction is very strongly acid to slightly alkaline.
The Cg horizon has hue of 10YR, value of 4 to 6 and chroma of 1. It is silty clay loam or silt loam and is very strongly acid to moderately acid.
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: McGirk soils are on concave footslopes, toeslopes, and sideslopes of hills that are at the heads of drainageways. They are on positions above floodplains or terraces and below upland soils formed in residuum or loess. They formed in colluvium and alluvium washed from the adjacent uplands. Slopes range from 1 to 12 percent. The mean annual temperature ranges from 54 to 57 degrees F, and mean annual precipitation ranges from 34 to 42 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Menfro, Moniteau, Union, Westerville, and Winfield soils. The Menfro and Winfield soils are fine-silty and are on adjacent higher positions. Moniteau soils are fine-silty and are on adjacent lower floodplains. Union soils have fragipans and are on higher nearby uplands. Westerville soils are fine-silty and are on adjacent floodplains.
DRAINAGE AND PERMEABILITY: Poorly drained. Runoff is medium. Permeability is slow. In undisturbed areas an apparent water table has an upper limit of 0.5 to 1.5 feet sometime from November to May in most years.
USE AND VEGETATION: Most areas are used to grow to corn, soybeans, and small grains or are used for hay. Native vegetation is mixed hardwoods.
DISTRIBUTION AND EXTENT: Central and southern Missouri. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Moniteau County, Missouri, 1953.
REMARKS: These soils were previously classified as Epiaqualfs, but further study shows that Endoaqualfs is the correct classification (1998 Keys to Taxonomy).
Current mapping has a slope range of mostly less than 5 percent. Mapping units with higher slope ranges in older surveys will be recorrelated during update activities.
Diagnostic horizons and features recognized in this series are:
ochric epipedon - the zone from the surface of the soil to a depth of 11 inches (Ap and BEg horizons);
argillic horizon - the zone from approximately 11 inches to 46 inches (Btg1, Btg2, Btg3, and Btg4 horizons);
aquic condition- redox features starting at 6 inches.