LOCATION TONTI AR+KS MOEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, active, mesic Typic Fragiudults
TYPICAL PEDON: Tonti gravelly silt loam, 4 percent slope, in a pasture. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; brown (10YR 5/3) gravelly silt loam; moderate medium granular structure; friable; many fine and medium roots; about 15 percent angular chert fragments less than 3 inches in diameter; very strongly acid; abrupt smooth boundary. (3 to 9 inches thick)
Btl--8 to 14 inches; yellowish brown (10YR 5/4) gravelly silt loam; moderate fine subangular blocky structure; firm; many fine roots; many thin clay films on peds faces; about 20 percent angular chert fragments less than 3 inches in diameter; extremely acid; clear smooth boundary. (4 to 8 inches thick)
Bt2--14 to 20 inches; yellowish brown (10YR 5/6) gravelly silty clay loam; few medium distinct pale brown (10YR 6/3) mottles; moderate medium subangular blocky structure; firm; few fine roots; few medium tubular pores; many thin clay films on ped faces; about 30 percent angular chert fragments less than 3 inches in diameter; extremely acid; clear wavy boundary. (4 to 8 inches thick)
2Btx--20 to 34 inches; light yellowish brown (10YR 6/4) very gravelly silt loam; common medium distinct very pale brown (10YR 7/3) mottles; moderate very coarse prismatic structure parting to moderate medium subangular blocky; firm, about 70 percent brittleness; few fine roots in light brownish gray (10YR 6/2) silt loam between prisms; many medium vesicular pores; continuous thick clay films on prism faces; about 35 percent angular fragments less than 3 inches in diameter; extremely acid; clear wavy boundary. (7 to 36 inches thick)
2Btl--34 to 49 inches; red (2.5YR 4/6) extremely gravelly clay; commom medium prominent light brownish gray (10YR 6/2) mottles; moderate medium blocky structure; firm; continuous thick clay films on ped faces and chert fragment; about 75 percent bedded, angular chert fragments, (25 percent, 3 to 8 inches in diameter and 50 percent, 3/4 to 3 inches in diameter); extremely acid; clear wavy boundary. (12 to 36 inches thick)
3Bt2--49 to 72 inches; dark red (2.5YR 3/6) very gravelly clay; common coarse prominent light brownish gray (10YR 6/2) mottles; moderate medium and coarse blocky structure; continuous thick clay films on faces of peds and fragments; about 40 percent angular chert fragments less than 3 inches in diameter; extremely acid; clear wavy boundary.
TYPE LOCATION: Benton County, Arkansas; 2 miles east of Lowell; NW1/4SE1/4SE1/4 sec. 6, T. 18 N., R. 29 W.
RANGE IN CHARACTERISTICS:
Depth to Bedrock: greater than 60 inches
Depth to fragipan: 15 to 31 inches
Note: Total rock fragment content ranges from 0 to 35 percent above the fragipan. Cobbles range from 0 to 10 percent.
Note: Reaction of the A horizon is very strongly acid to slightly acid and the B horizons are extremely acid to strongly acid.
A or Ap horizon
Hue: 10YR
Value: 3 to 5
Chroma: 1 to 4
Fine-earth: silt or silt loam
Note: Where the color value is 3, the horizon is less than 6 inches thick.
E, BA, or BE horizon (where present)
Hue: 7.5YR or 10YR
Value: 4 to 6
Chroma: 3 to 6
Fine-earth: silt or silt loam
Bt horizon
Hue: 5YR to 10YR
Value: 4 or 5
Chroma: 3 to 8
Fine-earth: silt loam or silty clay loam
Note: Some pedons have 10YR 6/2 clay depletions just above the fragipan.
Btx, 2Btx, or Ex horizon
Hue: 2.5YR to 10YR
Value: 4 to 6
Chroma: 3 to 8
Clay depletions (when present)
Hue: 10YR
Value: 6
Chroma: 1 or 2
Fine-earth: loam, silt loam, or silty clay loam
Total rock fragments: 20 to 85 percent; 20 to 85 percent gravel and 0 to 60 percent cobbles
2Bt or 3Bt horizon
Hue: 10R to 10YR
Value: 3 to 6
Chroma: 2 to 8
Fine-earth: loam, silty clay loam, silty clay, or clay
Total rock fragments: 0 to 90 percent; 0 to 90 percent gravel and 0 to 20 percent cobbles
COMPETING SERIES: These are the Califon, Delassus, Meckesville, and Watson series. Califon soils formed in old till or colluvium and have rock fragments derived predominantly from granitic gneiss. Delassus soils formed in loess with the underlying residuum weathered from granite or other igneous rock. Meckesville soils have 5YR or redder hues in the fragipan. Watson soils formed in till and contain sandstone and shale fragments.
GEOGRAPHIC SETTING: Tonti soils are nearly level to moderately sloping upland ridges of the Ozark Highlands and other areas with cherty limestone bedrock. Slopes range from 1 to 12 percent, but dominantly are less than 8 percent. The average annual temperature ranges from 54 to 57 degrees F., and average annual precipitation ranges from 42 to 46 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Captina and Clarksville, Johnsburg, Nixa, Noark and Peridge soils. Clarksville and Noark soils, which are on side slopes, have more than 35 percent rock fragments in the control section and do not have fragipans. Johnsburg soils, which are on slightly depressional slopes, have less than 10 percent rock fragments in the control section. Nixa soils, which are on ridgetops, have more than 35 percent rock fragments in the control section. Peridge soils, which are on adjacent upland slopes, have less than 10 percent rock fragments in the control section and do not have a fragipan.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is medium to very high. Permeability is moderate above the fragipan and slow within the fragipan. The saturated hydraulic conductivity is moderately high above the fragipan and very slow in the fragipan. These soils have a seasonally high perched water table that is within 18 to 30 inches of the soil surface from December through April.
USE AND VEGETATION: Used mainly for pasture and hay, but also cultivated for the production of soybeans, corn, vegetable crops, small grains, apples and grapes. Native vegetation was forest of oak, hickory, maple, elm, and in some places shortleaf pine.
DISTRIBUTION AND EXTENT: The Ozarks Highland region (MLRA 116A) of Arkansas, Missouri, Oklahoma, and Kansas. The series is of large extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: Benton County, Arkansas; 1973.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the surface to a depth of 8 inches (Ap horizon).
Argillic horizon - The zone from 8 to 72 inches (Bt1, Bt2, Btx, 2Bt1, and 2Bt2 horizons).
Fragipan - The zone from 20 to 34 inches (Btx horizon).
ADDITIONAL DATA: Characterization of the type location by University of Arkansas Soil Characterization Laboratory. Pedon No. S77AR-007-003.