LOCATION LLANOS PREstablished Series
TAXONOMIC CLASS: Fine, smectitic, isohyperthermic Entic Haplusterts
TYPICAL PEDON: Llanos clay - native pasture. (Colors are for moist soil unless otherwise stated.)
A1--0 to 5 inches; very dark brown (10YR 2/2) clay; moderate fine and medium granular structure; firm, slightly sticky, plastic; many fine roots; neutral; clear smooth boundary.
A2--5 to 10 inches; black (10YR 2/1) clay; weak medium subangular blocky structure; firm; slightly sticky, plastic; many fine roots; neutral; clear smooth boundary. (Total thickness of the A horizons range from 8 to 12 inches)
Bt--10 to 15 inches; very dark brown (10YR 2/2) and black (10YR 2/1) clay; weak course subangular blocky structure; very firm, sticky, plastic; few fine roots; many pressure faces on ped surfaces; about 10 percent, by volume, volcanic fragments; few faint clay films on ped faces; neutral; clear smooth boundary. (4 to 6 inches thick)
Btss--15 to 23 inches; brown (10YR 4/3) clay; moderate coarse subangular blocky structure; very firm, sticky, plastic; few fine roots; many pressure faces on ped surfaces; common medium intersecting slickensides having polished and grooved surfaces; about 5 percent, by volume, volcanic fragments; few faint clay films on faces of peds; neutral; clear wavy boundary.
Bss--23 to 29 inches; brown (10YR 4/3) clay; weak medium subangular blocky structure; firm; slightly sticky, plastic; few fine roots; many coarse intersecting slickensides having polished and grooved surfaces; about 10 percent, by volume, pebbles; neutral; clear wavy boundary. (Total thickness of the Btss and Bss horizons range from 15 to 24 inches)
C1--29 to 38 inches; brown (10YR 4/3) clay loam; massive; firm, slightly sticky, plastic; about 10 percent, by volume, pebbles; slightly alkaline; gradual wavy boundary.
C2--38 to 50 inches; brown (10YR 4/3) sandy clay loam; massive; friable, nonsticky, slightly plastic; about 10 percent, by volume, pebbles; slightly alkaline; gradual wavy boundary.
2C--50 to 60 inches; brown (10YR 4/3) sandy loam; single grained; very friable; slightly alkaline.
TYPE LOCATION: Caribe SCD, Puerto Rico. Approximately 250 meters south of kilometer marker 15.8 of P.R. Highway 150.
RANGE IN CHARACTERISTICS: Thickness of the solum ranges from 23 to 36 inches. Reaction is neutral or slightly alkaline throughout.
The A or Ap horizon has hue of 10YR, value of 2 or 3, and chroma of 1 to 3. Texture is clay loam or clay.
The upper Bt horizon has hue of 10YR, value of 2 or 3, and chroma of 2 or 3. The lower Bt horizon includes value of 4. Content of fragments range from 0 to 10 percent, by volume. Texture is clay.
The Btss and/or Bss horizons have hue of 10YR, value of 4, and chroma of 3 or 4. Content of fragments range from 0 to 10 percent, by volume. Texture is clay.
The upper C horizons have hue of 10YR, value of 4 and chroma of 4 to 6. Texture is clay loam or sandy clay loam. The lower C horizons have hue of 10YR, value of 4 to 6, and chroma of 4 to 6. Texture is loamy sand or sandy loam. Content of pebbles range from 0 to 10 percent, by volume.
COMPETING SERIES: There are no known series in the same family.
GEOGRAPHIC SETTING: Llanos soils are on foot slopes and alluvial fans. They formed in fine and moderately fine textured sediments that weathered from basic volcanic rocks. The climate is tropical semiarid. Slopes range from 2 to 12 percent. The average annual rainfall ranges from 25 to 45 inches and the average annual temperature ranges from 78 to 80 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Callabo and Jacana series. Callabo and Jacana soils are moderately deep and have mixed mineralogy. In addition, Callabo soils are on higher positions and Jacana soils are on similar positions.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Most areas are used for native pasture, cut grasses, tobacco, and subsistence crops. The vegetation consists of native and introduced grasses and shrubs.
DISTRIBUTION AND EXTENT: Semiarid areas of southern Puerto Rico. The series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: Ponce Survey Area, Puerto Rico; l971.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - zone from 0 to 15 inches (A1, A2, and Bt1 horizons).
Argillic horizon - zone from 10 to 23 inches (Bt1 and Bt2 horizons).
Vertic features - zone from 15 to 29 inches (Btss and Bss horizons).
ADDITIONAL DATA: NSSL Pedon No. S85PR-043-001. Sample by NSSL, Lincoln NE.