LOCATION MEXICO MOEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Vertic Epiaqualfs
TYPICAL PEDON: Mexico silt loam - on a 1 percent slope on an interfluve in a cultivated field at an elevation of 243 meters (798 feet). (Colors are for moist soil unless otherwise stated.)
Ap--0 to 23 centimeters (0 to 9 inches); very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; moderate medium and thin platy structure; friable; few fine roots; common fine tubular pores; few fine prominent yellowish brown (10YR 5/6) masses of oxidized iron; few fine faint black (10YR 2/1) iron-manganese concretions; slightly acid; abrupt smooth boundary. [13 to 23 centimeters (5 to 9 inches) thick]
Btg1--23 to 38 centimeters (9 to 14 inches); 70 percent dark grayish brown (10YR 4/2) and 30 percent grayish brown (10YR 5/2) silt loam; weak fine subangular blocky structure; friable; few fine roots; common fine and medium tubular pores; very few faint dark grayish brown (10YR 4/2) clay films on faces of peds; few distinct gray (10YR 6/1) silt coats on faces of peds; common fine prominent strong brown (7.5YR 5/6) and yellowish brown (10YR 5/8) masses of oxidized iron; few fine distinct black (10YR 2/1) iron-manganese concretions; friable; strongly acid; abrupt smooth boundary. [Thickness of the upper Btg horizon(s) is 0 to 23 centimeters (0 to 9 inches).]
Btg2--38 to 53 centimeters (14 to 21 inches); 70 percent dark grayish brown (10YR 4/2) and 30 percent gray (10YR 5/1) clay; moderate fine subangular blocky structure; friable; few very fine roots; few fine tubular pores; many distinct dark gray (10YR 4/1) clay films on faces of peds; few distinct very dark grayish brown (10YR 3/2) organoargillans on faces of peds; few distinct gray (10YR 6/1) silt coats on faces of peds; common fine prominent red (2.5YR 4/6) and strong brown (7.5YR 5/6) masses of oxidized iron; few fine faint black (10YR 2/1) iron-manganese concretions; very strongly acid; clear smooth boundary.
Btg3--53 to 69 centimeters (21 to 27 inches); grayish brown (10YR 5/2) silty clay; moderate fine subangular blocky structure; firm; few very fine roots; few fine tubular pores; 60 percent distinct grayish brown (10YR 5/2) clay films on faces of peds; common distinct very dark grayish brown (10YR 3/2) organoargillans on faces of peds and along surfaces of pores; many fine prominent yellowish brown (10YR 5/6) and few fine prominent yellowish red (5YR 4/6) masses of oxidized iron; few fine prominent black (10YR 2/1) iron-manganese concretions; very strongly acid; abrupt smooth boundary.
Btg4--69 to 86 centimeters (27 to 34 inches); grayish brown (10YR 5/2) silty clay; weak medium prismatic structure parting to weak fine subangular blocky; firm; few very fine roots; common fine tubular pores; common distinct dark grayish brown (10YR 4/2) clay films on faces of peds; common coarse prominent brown (7.5YR 4/4) and common fine prominent red (2.5YR 4/6) masses of oxidized iron; few fine prominent black (10YR 2/1) iron-manganese concretions; few fine prominent black (10YR 2/1) masses of manganese; strongly acid; abrupt smooth boundary. [Thickness of the middle Btg horizon(s) is 25 to 66 centimeters (10 to 26 inches).]
Btg5--86 to 107 centimeters (34 to 42 inches); light brownish gray (10YR 6/2) silty clay loam; moderate medium prismatic structure; firm; few very fine roots; common fine tubular pores; few faint gray (2.5Y 6/1) clay films on surfaces along pores; few coarse prominent strong brown (7.5YR 4/6) and few fine prominent dark yellowish brown (10YR 4/6) and reddish brown (5YR 4/4) masses of oxidized iron; few fine prominent black (10YR 2/1) masses of manganese on vertical faces of peds; few fine prominent black (10YR 2/1) iron-manganese concretions; strongly acid; gradual smooth boundary. [Thickness of the lower Btg horizon(s) is 13 to 50 centimeters (5 to 20 inches).]
2Btg6--107 to 135 centimeters (42 to 53 inches); gray (10YR 5/1) silty clay loam; moderate medium prismatic structure; firm; few very fine roots; few fine tubular pores; common faint gray (10YR 6/1) clay films on faces of peds; few medium prominent strong brown (7.5YR 4/6) and few fine prominent yellowish brown (10YR 5/6) masses of oxidized iron; few fine distinct black (10YR 2/1) masses of manganese; moderately acid; clear smooth boundary.
2Btg7--135 to 203 centimeters (53 to 80 inches); gray (10YR 5/1) silty clay loam; weak coarse prismatic structure parting to weak medium subangular blocky; firm; few fine tubular pores; many faint gray (2.5Y 5/1) clay films on faces of peds; common medium prominent dark yellowish brown (10YR 4/6) and brown (7.5YR 4/4) masses of oxidized iron; slightly acid.
TYPE LOCATION: Montgomery County, Missouri; about 3 miles east of Montgomery City; 341 meters (1,119 feet) east and 149 meters (489 feet) north from the southwest corner of sec. 23, T. 49 N., R. 5 W; New Florence USGS quadrangle, latitude 38 degrees 59 minutes 45 seconds N. and longitude 91 degrees 26 minutes 44 seconds W; UTM, Zone 15, 634616 easting, 4317461 northing, NAD 83.
RANGE IN CHARACTERISTICS:
Depth to top of the argillic horizon: 13 to 33 centimeters (5 to 13 inches)
Thickness of silt loam surface layers: 13 to 43 centimeters (5 to 17 inches)
Depth to top of the claypan: 18 to 46 centimeters (7 to 18 inches)
Particle-size control section: averages 38 to 50 percent clay, with at least one horizon having 45 to 60 percent
Depth to lithologic discontinuity (loamy sediments or 2Btg horizon): 76 to 152 centimeters (30 to 60 inches) in uneroded pedons and ranges from 71 to 152 centimeters (28 to 60 inches) in eroded pedons
Depth to till (3Btg horizon), where present: 152 to 203 centimeters (60 to 80 inches)
Depth to base of the argillic horizon: greater than 203 centimeters (80 inches)
Solum thickness: greater than 203 centimeters (80 inches)
Depth to carbonates: greater than 203 centimeters (80 inches)
Ap horizon
Hue: 10YR
Value: 2 or 3 moist; 4 or 5 dry
Chroma: 1 to 3
Texture: silt loam or silty clay loam
Average clay content: 15 to 30 percent
Average sand content: 3 to 10 percent
Reaction: moderately acid to neutral
BE horizon (where present)
Hue: 10YR
Value: 4 or 5
Chroma: 2 or 3
Texture: silt loam
Average clay content: 15 to 26 percent
Average sand content: 3 to 10 percent
Reaction: moderately acid to neutral
Upper Btg horizon
Some eroded pedons lack the upper Btg horizon
Hue: 10YR
Value: 3 to 6
Chroma: 2
Redoximorphic features: Red or yellowish red masses of iron accumulation normally present along with yellowish brown and strong brown masses of iron accumulation.
Texture: silt loam or silty clay loam
Average clay content: 25 to 35 percent
Average sand content: 4 to 12 percent
Reaction: strongly acid to neutral
Middle Btg horizon (claypan)
Hue: 10YR
Value: 4 to 6
Chroma: 1 to 3
Redoximorphic features: Brown and yellowish brown masses of iron accumulation, but the red masses diminish with increasing depth.
Texture: silty clay or clay
Average clay content: 40 to 60 percent
Average sand content: 0 to 4 percent
Reaction: very strongly acid to strongly acid
Lower Btg horizon
Hue: 10YR or 2.5Y
Value: 4 to 6
Chroma: 1 to 3
Redoximorphic features: Brown and yellowish brown masses of iron accumulation, but the red masses diminish with increasing depth.
Texture: silty clay loam or silt loam
Average clay content: 28 to 38 percent
Average sand content: 0 to 4 percent
Reaction: very strongly acid to neutral
2Btg horizon
Hue: 10YR or 2.5Y
Value: 4 to 6
Chroma: 1 to 4
Texture: dominantly silty clay loam, silt loam, or silty clay, with clay loam in some pedons
Average clay content: 24 to 38 percent
Average sand content: 4 to 25 percent
Reaction: very strongly acid to neutral
COMPETING SERIES: These are the Bucknell, Gifford, Kilwinning, Kniffin, Leonard, Pershing, Rathbun, Rinda, Shields, and Stateline series. Bucknell soils are less than 203 centimeters (80 inches) to the base of the argillic horizon and formed in paleosols derived from till. Gifford soils formed in loess and silty sediments or alluvium on stream terraces. Kilwinning soils formed entirely in loess, allow 2.5Y hue in the upper Btg horizon, and are typically less acid in the lower part of the series control section. Kniffin, Pershing and Rathbun soils are more than 152 centimeters (60 inches) to a lithologic discontinuity and formed in more than 152 centimeters (60 inches) of loess. Leonard soils are 30 to 76 centimeters (12 to 30 inches) deep to a paleosol containing till pebbles. Rinda soils are less than 46 centimeters (18 inches) to a lithologic discontinuity and formed in thin loess or silty sediments and the underlying paleosol formed in till. Shields soils have carbonates above a depth of 152 centimeters (60 inches) and formed in till. Stateline soils are less than 203 centimeters (80 inches) to the base of the argillic horizon and formed in loess or loamy sediments and the underlying clayey paleosol.
GEOGRAPHIC SETTING: Mexico soils are on ridges and hillsides of dissected till plains. These soils formed in 71 to 152 centimeters (28 to 60 inches) of loess over loamy sediments derived from pre-Illinoian till. Slopes range from 0 to 4 percent. The mean annual temperature ranges from 10 to 13 degrees C (50 to 55 degrees F), and mean annual precipitation ranges from 890 to 1020 millimeters (35 to 40 inches).
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Armstrong, Gara, Leonard, Lindley and Putnam soils. The somewhat poorly drained Armstrong, the moderately well drained Gara, and the well drained Lindley soils have more sand in the upper part of the solum and are down slope. Leonard soils are 30 to 76 centimeters (12 to 30) inches to a paleosol containing till pebbles. Putnam soils have an abrupt textural change. Leonard soils are down slope and Putnam soils are on the main divides upslope from Mexico soils.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Poorly drained. The potential for runoff is high to very high. Permeability is very slow. Saturated hydraulic conductivity (Ksat) is 0.01 to 0.42 micrometers per second. In undisturbed areas a perched water table has an upper limit of 15 to 61 centimeters (0.5 to 1.5 feet) during December to May in most years.
USE AND VEGETATION: Most areas are used to grow corn, soybeans, and small grains. Native vegetation is tall prairie grass.
DISTRIBUTION AND EXTENT: The Central Claypan Areas, MLRA 113, of northeast Missouri. The series is of large extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: St. Charles County, Missouri, 1952.
REMARKS: With this revision, the Mexico Series is reclassified as Fine, smectitic, mesic Vertic Epiaqualfs and the type location is moved to a more representative site. This series was previously classified as Fine, smectitic, mesic Aeric Vertic Epiaqualfs. The previous typical pedon lacked lab data and the location was uncertain. This more representative pedon with lab data is approximately 2.4 miles east by northeast of the previous type location.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of 23 centimeters (9 inches) (Ap horizon);
Argillic horizon - the zone from 23 to 203 centimeters (9 to 80 inches) (Btg, and 2Btg horizons).
Claypan the zone from 36 to 86 centimeters (14 to 34 inches) (Btg2, Btg3, and Btg4 horizons).
Lithologic discontinuity occurs at a depth of 107 centimeters (42 inches) (top of 2Btg1 horizon).
ADDITIONAL DATA: LAB SAMPLE NUMBER M0513904 (University of Missouri Lab) is data for the typical pedon. LAB SAMPLE NUMBERS MO500706, MO500708, MO500709, MO502703, MO511302, MO511303, MO511304, MO513907, MO516302, MO521903, and MO602701 are additional data used for the series range in characteristics.