LOCATION JONCA MOEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, active, mesic Oxyaquic Fragiudalfs
TYPICAL PEDON: Jonca silt loam - on a 6 percent convex east facing point ridge slope in a pastured woodlot at an elevation of 885 feet. (Colors are for moist soil unless otherwise stated.)
A--0 to 7 inches; dark brown (10YR 4/3) silt loam; moderate fine granular structure; friable; many fine roots; neutral; clear wavy boundary. (5 to 8 inches thick)
BA--7 to 11 inches; brown (7.5YR 5/4) silty clay loam with 20 percent mixing of dark brown (10YR 4/3) silt loam; moderate fine subangular blocky structure; friable; many fine roots; strongly acid; clear wavy boundary. (0 to 8 inches thick)
Bt1--11 to 24 inches; brown (7.5YR 4/4) clay loam; moderate medium subangular blocky structure; firm; many fine roots; few thin patchy clay films; very strongly acid; clear smooth boundary. (10 to 21 inches thick)
2Bt2--24 to 30 inches; brown (7.5YR 4/4) loam; weak fine subangular blocky structure; firm; common fine roots; few thin discontinuous clay films in pores and cavities; many medium and coarse distinct grayish brown (10YR 5/2) iron depletions and clay depletions; very strongly acid; gradual boundary. (0 to 12 inches thick)
2Btx--30 to 48 inches; brown (7.5YR 5/4) loam; dark grayish brown (10YR 4/2) clay loam filling 10-15 mm cracks about 1 foot apart; very coarse prismatic structure with massive interiors; very firm; brittle when moist; few fine roots along vertical cracks; brown (7.5YR 4/4) clay films in channels and cavities; common medium distinct grayish brown (10YR 5/2) iron depletions; very strongly acid; gradual boundary. (10 to 30 inches thick)
3Bt--48 to 68 inches; reddish brown (5YR 4/4) sandy loam; weak and moderate fine subangular blocky structure; firm; few thick patchy brown (7.5YR 4/4) clay films on surfaces of peds and along vertical channels and cracks; very strongly acid; clear wavy boundary. (10 to 30 inches thick)
3R--68 inches; sandstone
TYPE LOCATION: St. Francois County, Missouri; about 2 miles east of Farmington, 2,480 feet south and 2,140 feet east of the northwest corner of sec. 28, T. 36 N., R. 6 E; USGS Farmington, Missouri quadrangle;, lat. 37 degrees 47 minutes 49 seconds N. and long. 90 degrees 22 minutes 32 seconds W.
RANGE IN CHARACTERISTICS: The thickness of the solum is 56 to over 80 inches. Depth to bedrock is 60 to more than 100 inches. Depth to the fragipan is 24 to 40 inches, and is about 10 to 30 inches thick. Rock fragments larger than 3 inches in size average about 5 percent of the mass and are only present below the fragipan. Rock fragments less than 3 inches in size are absent above the fragipan and average 0 to 15 percent within and below the fragipan.
The A horizon has hue of 10YR or 7.5YR, value of 3 or 4, and chroma of 2 or 3. It is silt loam unless eroded, in which case it is silty clay loam or clay loam. Reaction is very strongly acid to medium acid, and ranges to neutral where limed.
The BA or E horizons, where present, have hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 4.
The Bt horizon has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 3 to 6. It is clay loam, loam, silt loam, or silty clay loam and averages between 27 and 35 percent clay and 15 to 25 percent sand. It is extremely strongly acid to strongly acid.
The 2Bt horizon and 2Btx horizons have hue of 10YR, 7.5YR, or 5YR, value of 4 or 5, and chroma of 4 to 6. Mottles have hue of 10YR, value of 5 or 6, and chroma of 2 or 3. The 2Bt horizon is loam, clay loam, or silty clay loam and the 2Btx horizon is loam, sandy loam, fine sandy loam, or sand clay loam. Reaction for both horizons range from extremely acid to strongly acid. Some pedons have a 2E'2 or 3Bt horizon above the fragipan.
The 3Bt horizon has hue of 10YR, 7.5YR, 5YR, or 2.5YR, value of 3 to 5, and chroma of 4 to 6. It is sandy loam, sandy clay loam or clay loam. Reaction is very strongly acid to slightly acid. It has a significant accumulation of translocated clays in the form of distinct clay films.
COMPETING SERIES: These are the Comly, Gatton, Homewood, Readington, and Wooster series. Comly soils have shaly or very shaly silt loam or loam fragipans. Gatton soils have a fragipan at 20 to 30 inches. Homewood soils have glacial erratics. Readington soils have hues redder than 7.5YR in the B2 horizon. Wooster soils have coarse fragments throughout the solum. In addition, Wooster soils lack low chroma mottles above the fragipan.
GEOGRAPHIC SETTING: Jonca soils are on convex upland ridges, sloping point ridges, side slopes, and less commonly on foot slopes. Slope range from 2 to 9 percent. The soils formed in a thin layer of loess, colluvium, and the underlying residuum weathered from sandstone. The mean annual temperature ranges from 54 to 57 degrees F, and mean annual precipitation ranges from 40 to 45 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lily, Ramsey, and the Lamotte soils. Lily and Ramsey soils are on steeper side slopes at lower elevations and lack fragipans. The Lamotte soils lack fragipans and occur on similar landscapes.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff potential is high. Permeability is moderate above the fragipan and slow within the fragipan.
USE AND VEGETATION: Most areas are cleared and used for fescue pasture. A very small area is cultivated to corn and sorghum. Native vegetation was oak and hickory forest.
DISTRIBUTION AND EXTENT: Northeastern Ozarks (MLRA 116A and 116B) of Missouri. The series is moderate in extent, more than 30,000 acres have been mapped to date.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: St. Francois County, Missouri, 1979.
REMARKS: Diagnostic horizons and features in this pedon are:
1. Ochric epipedon - the zone from the surface of the soil to 11 inches (A and BA horizons)
2. Argillic horizon - the zone from 11 to 30 inches (Bt1 and 2Bt2 horizons)
3. Fragipan - the zone from 30 to 48 inches (2Bx horizon)