LOCATION AGNOS AR+MOEstablished Series
TAXONOMIC CLASS: Very-fine, mixed, active, mesic Typic Hapludults
TYPICAL PEDON: Agnos very gravelly silt loam in woodland. (Colors are for moist soil unless otherwise stated.)
A--0 to 2 inches; very dark grayish brown (10YR 3/2) very gravelly silt loam; moderate fine granular structure; friable; many fine and medium roots; about 40 percent by volume angular chert fragments less than 3 inches in diameter; strongly acid; abrupt smooth boundary. (1 to 4 inches thick)
E--2 to 10 inches; pale brown (10YR 6/3) gravelly silt loam; weak medium subangular blocky structure; friable; many fine and medium roots; common fine and medium pores; about 30 percent by volume angular chert fragments less than 3 inches in diameter; very strongly acid; clear smooth boundary. (4 to 10 inches thick)
Bt1--10 to 19 inches; strong brown (7.5YR 5/8) clay; moderate medium angular blocky structure; very firm; common fine and medium roots; common fine pores; many distinct clay films on faces of peds; about 10 percent by volume angular chert fragments less than 3 inches in diameter; very strongly acid; clear smooth boundary.
Bt2--19 to 34 inches; strong brown (7.5YR 5/8) clay; common medium distinct very pale brown (10YR 7/3) iron depletions; moderate medium angular blocky structure; very firm; common fine and medium roots; few fine pores; many distinct clay films on faces of peds; about 5 percent by volume angular chert fragments less than 3 inches in diameter; very strongly acid; gradual wavy boundary.
Bt3--34 to 42 inches; yellowish brown (10YR 5/6) clay; common medium distinct light gray (10YR 7/2) iron depletions and common medium prominent red (2.5YR 4/6) iron accumulations; strong medium angular blocky structure; very firm; few fine roots; many distinct clay films on faces of peds and on dolomite fragments; about 10 percent by volume soft dolomite fragments less than 3 inches in diameter; very strongly acid; gradual wavy boundary. (Combined thickness of the Bt horizon ranges from 26 to 55 inches.)
BC--42 to 57 inches; ped interiors are brownish yellow (10YR 6/8) and light brownish gray (10YR 6/2) and ped exteriors are light olive gray (5Y 6/2) clay with medium prominent yellowish brown (10YR 5/4) iron accumulations; moderate coarse platy structure parting to moderate medium angular blocky; about 10 percent by volume soft dolomite fragments less than 3 inches in diameter; very strongly acid; clear wavy boundary. (0 to 15 inches thick)
Cr--57 to 72 inches; interiors are strong brown (7.5YR 5/6) and exteriors are light olive gray (5Y 6/2) soft, platy dolomite; platy and angular blocky rock structure; extremely firm; very strongly acid.
Type location: Fulton County, Arkansas; about 2.5 miles northwest of Salem on Highway 62 and then 1 mile south on county road in SE1/4SE1/4NE1/4 sec. 19, T. 20 N., R. 8 W.
RANGE IN CHARACTERISTICS: The thickness of the solum and depth to soft bedrock ranges from 40 to 60 inches. Depth to hard bedrock ranges from 60 to 72 inches or more. Reaction ranges from strongly acid to slightly acid in the A and E horizons and extremely acid to strongly acid in the B, BC and C horizons. Coarse fragment content, mainly chert and dolomite, ranges from 15 to 60 percent by volume in the A and E horizons and 1 to 15 percent by volume in the B, BC and C horizons.
The A horizon has hue of 10YR, value of 3 or 4, and chroma of 2 or 3. Some pedons have Ap horizons with hue of 10YR, value of 4 or 5 and chroma of 3 or 4. Texture is very gravelly silt loam or very gravelly loam, gravelly silt loam, gravelly loam, cobbly silt loam, cobbly loam, stony silt loam, and stony loam.
The E horizon has hue of 10YR, value 5 or 6, and chroma
of 2, 3 or 4. Texture is very gravelly silt loam, gravelly
silt loam, very gravelly loam, or gravelly loam.
The upper Bt horizons have hue of 10YR or 7.5YR, value of 5, and chroma of 4, 6 or 8. Iron accumulations are in shades of brown. Texture is silty clay or clay.. The lower Bt horizons have hue of 10YR or 7.5YR, value of 5 or 6, and chroma of 4, 6 or 8. Iron accumulations and depletions are in shades of red, brown, yellow, or gray, or it is a variegated horizon in these colors. Texture is clay. The particle-size control section contains more than 60 percent clay.
The BC horizon has hue of 10YR or 7.5YR, value of 5 or 6, and chroma of 4, 6 or 8 with mottles in shades of red, brown gray or yellow, or it is a mottled horizon in these shades. Texture is clay or silty clay.
The C horizon, where present, has hue of 10YR or 7.5YR, value of 5, 6 or 7, and chroma of 4, 6 or 8 with mottles in shades of brown, red, gray or yellow, or it is a mottled horizon in these shades. Texture is clay or silty clay.
The Cr horizon is weathered, soft dolomite in shades of brown, yellow and gray. Clayey material is in voids or fractures of weathered bedrock.
COMPETING SERIES: The Gassville series is in this family. Gassville soils have hard bedrock at 40 to 60 inches and Bt horizons with hues of 5YR or redder.
GEOGRAPHIC SETTING: Agnos soils are on nearly level to steep upland ridgetops and sideslopes of the Salem Plateau in the Ozark Highlands; MLRA 116A.in northern Arkansas and southern Missouri They formed in silty and clayey residuum weathered from dolomite bedrock with discontinuous beds and isolated nodules of chert. Mean annual precipitation ranges from 42 to 48 inches, average annual temperature ranges form 52 degrees to 57 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Arkana, Doniphan, Gassville, Gepp and Moko series. Arkana and Gepp soils, which are on lower landscapes, have higher base saturation. In addition, Arkana soils have hard bedrock at less than 45 inches and Gepp soils have sola more than 60 thick. Doniphan soils, which are on slightly higher landscapes have sola greater than 60 inches thick. Gassville soils which are on slightly lower landscapes, have B horizons with redder hues, 30 to 40 inch sola and hard bedrock at 40 to 60 inches. Moko soils, which are on lower landscapes, are less than 20 inches deep to bedrock and lack argillic horizons.
DRAINAGE AND PERMEABILITY: Agnos soils are well drained. Runoff is medium to very rapid and permeability is very slow.
USE AND VEGETATION: Most areas are used for pasture and hayland with dominant species of bermudagrass and tall fescue. Wooded tracts are in upland oaks, eastern redcedar, and shortleaf pine.
DISTRIBUTION AND EXTENT: Ozark Highlands of Arkansas and Missouri. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: Lawrence County, Arkansas, 1973.
REMARKS: Diagnostics horizons and features recognized in this pedon are:
Ochric epipedon--zone from the surface to 10 inches.
Argillic horizon--zone from 10 to 57 inches.
Paralithic contact--zone from 57 to 72 inches.
ADDITIONAL DATA: Characterization of the typical pedon by the University of Arkansas Soil Characterization Lab. (pedon number S78AR049-3) and the National Soil Survey Lab. (lab numbers 80P1914-1919).