LOCATION FROGSBORO NC
Established Series
JWL/RJH/DTA
11/2025
FROGSBORO SERIES
MLRA(s): 136 (thermic part)
Soil Survey Regional Office (SSRO) Responsible: Southeast
Depth Class: Very deep
Agricultural Drainage Class: Somewhat poorly drained
Index Surface Runoff: Medium
Saturated Hydraulic Conductivity Class: Low
Shrink-Swell Potential: Very high
Landscape: Piedmont uplands
Landform: Ridges, flats, depressions
Parent Material: Residuum from diabase, diorite, gabbro, and other rocks high in ferro-magnesium minerals
Slope: 0 to 15 percent
Elevation (type location): 700 feet
Mean Annual Air Temperature (type location): 15 degrees C (59 degrees F)
Mean Annual Precipitation (type location): 1118 millimeters (44 inches)
TAXONOMIC CLASS: Very-fine, smectitic, thermic Aeric Vertic Epiaqualfs
TYPICAL PEDON: Frogsboro sandy loam on a 1 percent slope in a mixed hardwood and pine forest. (Colors are for moist soil unless otherwise stated.)
A--0 to 10 centimeters (0 to 4 inches); dark brown (10YR 3/3) fine sandy loam; moderate fine granular structure; friable, slightly sticky, slightly plastic; many fine, medium, and coarse roots; few fine tubular pores; 5 percent medium prominent strong brown (7.5YR 4/6) masses of oxidized iron; and 15 percent medium distinct dark gray (10YR 4/1) mottles, throughout; moderately acid, pH 6.0; clear wavy boundary.
EB--10 to 25 centimeters (4 to 10 inches); grayish brown (2.5Y 5/2) fine sandy loam; weak coarse granular structure; friable, slightly sticky, slightly plastic; many fine, medium, and coarse roots; few fine tubular pores; 15 percent medium prominent strong brown (7.5YR 5/6) masses of oxidized iron; 1 percent basalt fragments; moderately acid, pH 6.0; clear wavy boundary.
Btss1--25 to 36 centimeters (10 to 14 inches); strong brown (7.5YR 5/6) clay; strong coarse prismatic parts to strong medium angular blocky structure; very firm, very sticky, very plastic; many fine, medium, and coarse roots; common medium tubular pores; 15 percent discontinuous distinct light brownish gray (10YR 6/2) and dark yellowish brown (10YR 4/4) pressure faces on vertical faces of peds and 20 percent distinct light brownish gray (10YR 6/2) and dark yellowish brown (10YR 4/4) clay films on all faces of peds; 10 percent faint slickensides on vertical faces of peds; 10 percent medium prominent light brownish gray (10YR 6/2) iron depletions and 20 percent coarse prominent greenish gray (5GY 5/1) iron depletions; strongly acid, pH 5.5; gradual wavy boundary.
Btss2--36 to 58 centimeters (14 to 23 inches); yellowish brown (10YR 5/6) clay; strong coarse prismatic parts to strong very coarse angular blocky structure; very firm, very sticky, very plastic; common fine, medium, and coarse roots; few medium tubular pores; 35 percent discontinuous distinct light brownish gray (10YR 6/2) pressure faces on vertical faces of peds and 40 percent distinct light brownish gray (10YR 6/2) and yellowish brown (10YR 5/4) clay films on all faces of peds; 10 percent faint slickensides on vertical faces of peds; 10 percent medium faint strong brown (7.5YR 5/6) masses of oxidized iron and 10 percent coarse prominent greenish gray (5GY 5/1) iron depletions and 15 percent fine prominent light brownish gray (10YR 6/2) iron depletions; strongly acid, pH 5.5; gradual wavy boundary.
Btss3--58 to 79 centimeters (23 to 31 inches); yellowish brown (10YR 5/6) clay; strong coarse prismatic parts to strong very coarse angular blocky structure; very firm, very sticky, very plastic; common fine, medium, and coarse roots; 15 percent discontinuous distinct light brownish gray (10YR 6/2) and yellowish brown (10YR 5/4) pressure faces on vertical faces of peds and 20 percent distinct yellowish brown (10YR 5/4) and light grayish olive (10Y 6/2) clay films on all faces of peds; 10 percent faint slickensides on vertical faces of peds; 5 percent medium faint yellowish brown (10YR 5/4) clay depletions and 10 percent medium prominent light brownish gray (10YR 6/2) iron depletions; strongly acid, pH 5.5; gradual wavy boundary.
Btss4--79 to 107 centimeters (31 to 42 inches); yellowish brown (10YR 5/6) clay; strong coarse prismatic parts to strong very coarse angular blocky structure; very firm, very sticky, very plastic; common fine, medium, and coarse roots; 20 percent distinct yellowish brown (10YR 5/4) clay films on vertical faces of peds; 10 percent faint slickensides on vertical faces of peds; 2 percent medium faint light brownish gray (10YR 6/2) iron depletions and 5 percent medium prominent yellowish brown (10YR 5/4) clay depletions; moderately acid, pH 6.0; gradual wavy boundary.
BC--107 to 117 centimeters (42 to 46 inches); yellowish brown (10YR 5/8) loam; weak coarse angular blocky structure; friable, slightly sticky, slightly plastic; very few fine and medium roots; 2 percent basalt fragments; moderately acid, pH 6.0; clear smooth boundary.
C1--117 to 150 centimeters (46 to 59 inches); yellowish brown (10YR 5/8) gravelly sandy loam; massive; friable, slightly sticky, slightly plastic; very few fine and medium roots; 25 percent basalt fragments; neutral, pH 7.0; clear smooth boundary.
C2--150 to 190 centimeters (59 to 75 inches); light olive brown (2.5Y 5/4) sandy loam; massive; friable, slightly sticky, slightly plastic; 5 percent basalt fragments; neutral, pH 7.0; clear smooth boundary.
C3--190 to 203 centimeters (75 to 80 inches); yellowish brown (10YR 5/6) gravelly fine sandy loam; massive; very friable, nonsticky, nonplastic; 10 percent basalt fragments; moderately alkaline, pH 8.0.
TYPE LOCATION: Caswell County, North Carolina; about 6.3 miles southwest of Yanceyville on NC Highway 158 to NC Highway 150, about 1.3 miles southwest on NC Highway 150 to Secondary Road 1128; about 3.8 miles south on Secondary Road 1128 to Secondary Road 1133; about 0.5 mile southwest on Secondary Road 1133 to Secondary Road 1104; about 2 miles south on Secondary Road 1104 to gated farm path; about 0.30 mile east on farm path; about 125 feet north on field path to southeastern corner of woods; about 80 feet north along edge of woods; about 140 feet west, in woods; USGS Cherry Grove, North Carolina topographic quadrangle.
Latitude--36.281944
Longitude-- -79.437778
Datum--WGS84
RANGE IN CHARACTERISTICS:
Solum thickness: 102 to 152 centimeters (40 to 60 inches)
Depth to bedrock: Greater than 152 centimeters (60 inches)
Depth to Seasonal High Water Table: 30 to 46 centimeters (12 to 18 inches inches)
Rock Fragment Content: 0 to 35 percent, by volume, throughout
Mica Content: 0 to 20 percent, by volume, in the B and C horizons
Soil Reaction: Strongly acid to neutral in the A and BE horizons, strongly acid to slightly alkaline in the Bt and BC horizons, and slightly acid to moderately alkaline in the C horizon.
Many pedons have few to many dark concretions throughout the profile. Many pedons have few to many dark mottles or soft bodies in the B and C horizons.
RANGE OF INDIVIDUAL HORIZONS:
A or Ap horizon:
Color--hue of 10YR to 5Y, value of 3, chroma of 2 or 3
Texture (fine-earth fraction)--sandy loam, fine sandy loam, loam, silt loam, or clay loam
E or EB horizon:
Color--hue of 10YR to 2.5Y, value of 4 or 5, chroma of 2 to 4
Texture (fine-earth fraction)--sandy loam, fine sandy loam, loam, silt loam, or clay loam
Btss horizon (upper part) or Bt horizon (if it occurs)
Color--hue of 7.5YR to 2.5Y, value of 3 to 6, chroma of 2 to 6
Btss (middle and lower part):
Color--hue of 10YR to 5Y, value of 4 to 6, chroma of 2 to 6
Texture--clay
Pressure faces--few to common and slickensides are usually present.
BC horizon:
Color--hue of 10YR to 5Y, value of 4 to 6, chroma of 3 to 8. Mottles may occur in shades of red brown, or yellow.
Texture--clay loam, loam, or sandy clay loam.
C horizon:
Color--hue of 10YR to 5Y, value of 4 to 6, chroma of 3 to 8 or may be multicolored in shades of white, gray, brown, yellow, or black.
Texture--sandy loam, fine sandy loam, very fine sandy loam, or sandy clay loam.
COMPETING SERIES: There are no known soils in this family.
GEOGRAPHIC SETTING:
Landscape: Piedmont upland
Landform: Ridge, flat, or depression
Parent Material: Residuum from diabase, diorite, gabbro, and other rocks high in ferro-magnesium minerals.
Slope: 0 to 15 percent but generally less than 6 percent
Elevation:
Frost Free Period: 190 to 225 days
Mean Annual Air Temperature: 59 to 66 degrees F.
Mean Annual Precipitation: 37 to 60 inches
GEOGRAPHICALLY ASSOCIATED SOILS:
Armenia soils--are poorly drained; on similar landscapes
Brewback soils--are moderately deep to soft bedrock and have mixed mineralogy; on similar landscapes
Crawfordville soils--are moderately deep to soft bedrock, have mixed mineralogy, and a high shrink-swell potential; on similar landscapes
Cullen soils--are well drained, have a red subsoil, have mixed mineralogy, and lack the high base saturation in the lower subsoil; on similar landscapes
Enon soils--are well drained and have mixed mineralogy; on similar landscapes
Iredell soils--are moderately well drained and have mixed mineralogy; on similar landscapes
Mecklenburg soils--are well drained and have a red subsoil, on similar landscapes
Pittsboro soils --are moderately well drained and are moderately deep to hard bedrock; on similar landscapes
Sedgefield soils--have a slow permeability and have a high shrink-swell potential; on similar landscapes
Virgilina soils--are moderately well drained, are moderately deep to hard bedrock, and have a high shrink-swell potential; on similar landscapes
Wilkes soils--are well drained and are shallow to soft bedrock; usually on side slopes
Winnsboro soils--are well drained and are deep to soft bedrock; on similar landforms
Wynott soils--are well drained and are moderately deep to soft bedrock; on similar landscapes
DRAINAGE AND PERMEABILITY:
Depth class: Very deep
Drainage class (Agricultural): Somewhat poorly drained
Flooding Frequency and Duration: None
Ponding Frequency and Duration: Rare, short duration
Index Surface Runoff: Very high
Permeability: Very slow
Shrink-Swell Potential: Very high
USE AND VEGETATION:
Major Uses: Woodland
Dominant Vegetation: Where cultivated--corn, soybeans, hay, and pasture. Where wooded--Eastern red cedar, post oak, white oak, and loblolly pine. Understory species include eastern redbud.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Auburn, Alabama
DISTRIBUTION AND EXTENT:
Distribution: North Carolina and possibly Virginia
Extent: Small
SERIES ESTABLISHED: Caswell County, North Carolina, 2016.
REMARKS: This series was formerly included with Iredell soils. Iredell soils are moderately well drained and have mixed mineralogy. The November 2025 revision updated the format. No data was changed.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface of the soil to 10 inches (A and EB horizon)
Argillic horizon - the zone from 10 to 42 inches (Btss horizons)
Aquic conditions - the zone from 4 to 23 inches (BE, Btss1, and Btss2 horizons)
Aeric feature - the zone from 10 to 30 inches (Btss1, Btss2, Btss3 horizons)
Vertic feature - linear extensibility of 6 cm or more (Btss horizons)
ADDITIONAL DATA:
Database Information:
Typical Pedon Data Mapunit ID--670252
Benchmark Status: No
Lab data: S08NC-033-001-01-011
TABULAR SERIES DATA:
SOI-5 Soil Name Slope Airtemp FrFr/Seas Precip Elevation
NC Frogsboro 0-15 58-66 180-225 40-60 400-800
SOI-5 FloodL FloodH Watertable Kind Months Bedrock Hardness
NC NONE 1.0-1.5 PERCHED JAN-MAR >60
SOI-5 Depth Texture 3-Inch No-10 Clay% -CEC-
NC 0-10 FSL SL L 0-5 85-100 8-20 4-15
NC 0-10 SCL 0-5 85-100 20-35 10-25
NC 10-42 SC CL C 0-5 95-100 35-60 15-35
NC 42-46 L SCL CL 0-5 90-100 10-35 4-20
NC 46-80 VAR - - - -
SOI-5 Depth -pH- O.M. Salin Permeab Shnk-Swll
NC 0-10 4.5-6.5 .5-2. 0-0 2.0-6.0 LOW
NC 0-10 4.5-6.5 .5-2. 0-0 0.6-2.0 LOW
NC 10-42 4.5-6.5 0.-.5 0-0 0.06-0.2 VERY HIGH
NC 42-46 5.6-8.4 0.-.5 0-0 0.6-2.0 MODERATE
NC 46-80 - - - -
________________________________________
National Cooperative Soil Survey
U.S.A.