LOCATION PONCENA PREstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, isohyperthermic Typic Calciusterts
TYPICAL PEDON: Poncena clay - pasture. (Colors are for moist conditions)
Ap--0 to 11 inches; black (N 2/0) clay; moderate medium granular structure; hard, firm, sticky, plastic; many fine roots; few fine volcanic rock fragments; neutral; gradual wavy boundary. (8 to 14 inches thick)
ABss--11 to 18 inches; mixed black (N 2/0) and very dark grayish brown (10YR 3/2) clay; massive when wet, weak medium subangular blocky structure when dry; firm; sticky, plastic; few fine roots; common distinct slickensides having polished and grooved surfaces; few fine volcanic rock fragments; neutral; gradual wavy boundary. (5 to 8 inches thick)
Bss--18 to 30 inches; dark brown (10YR 3/3) clay; weak coarse subangular blocky structure; firm; sticky, plastic; few fine roots; many distinct intersecting slickensides having polished and grooved surfaces; few fine volcanic rock fragments; neutral; clear irregular boundary. (8 to 12 inches thick.)
Bkss--30 to 38 inches; grayish brown (2.5Y 5/2) clay; weak coarse subangular blocky structure; firm; sticky, plastic; few distinct slickensides having polished and grooved surfaces; few fine weathered volcanic rock fragments; many medium and coarse distinct white (10YR 8/2) soft masses of secondary calcium carbonate; strongly effervescent; moderately alkaline; gradual wavy boundary. (6 to 20 inches thick)
C--38 to 60 inches; about 50 percent dark brown (10YR 4/3) weathered volcanic rock and about 50 percent white (N 8/0) calcareous earth; clay loam; massive; friable; few black (10YR 2/1) pebbles; strongly effervescent; moderately alkaline.
TYPE LOCATION: Cabo Rojo Municipality, Puerto Rico. Approximately 0.6 mile east of the intersection of P.R. 101 and P.R. Hwy. 103, about 222 feet south of P.R. Hwy. 101 in pasture. Puerto Real topographic quadrangle; lat. 18 degrees 01 minute 47 seconds N.; long. 67 degrees 07 minutes 48 seconds W. PRD 1940.
RANGE IN CHARACTERISTICS: Depth to the weathered volcanic rock is 30 to 50 inches. Depth to the Bkss horizon is 21 to 34 inches. Reaction is neutral to moderately alkaline in throughout.
The A horizon has hue of 10YR, value of 2 or 3, and chroma of 1 or less; or it is neutral with value of 2 or 3. Texture is clay loam or clay.
The Bss horizon has hue of 10YR or 2.5Y, value of 3 to 5, and chroma of 2 to 4.
The Bkss horizon has hue of 10YR or 2.5Y, value of 4 to 7, and chroma of 2 to 4.
The C horizon has hue of 10YR or 2.5Y, value of 4 or 5, and chroma of 2 to 4 for the weathered volcanic rock. The calcareous material has hue of 7.5YR or 10YR, value of 7 or 8, and chroma of 2 or less; or it is neutral with value of 7 or 8.
COMPETING SERIES: There are no competing series in the same family.
GEOGRAPHIC SETTING: Poncena soils are on terraces and alluvial fans. They formed in material that weathered from volcanic rocks and limestone. The climate is tropical semiarid. Slopes range from 0 to 12 percent. The average annual temperature ranges from 78 to 80 degrees F., and the average annual precipitation ranges from 35 to 50 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aguirre, Cartagena, Descalabrado, Guanica, Fraternidad and Jacana soils. None of these soils have a calcic horizon. Aguirre, Cartagena, and Guanica soils are somewhat poorly drained. Descalabrado soils have hard rock at shallow depths. Fraternidad soils have browner colors. Jacana soils have a paralithic contact at moderate depths.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow permeability.
USE AND VEGETATION: Poncena soils are used for sugarcane and for pasture. The main pasture species are guineagrass, stargrass, pangolagrass, and buffelgrass.
DISTRIBUTION AND EXTENT: Semiarid areas of Puerto Rico. The soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: Puerto Rico, 1942.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - zone from 0 to 30 inches (Ap, ABss and Bss horizons).
Slickensides and vertic features - zone from 18 to 38 inches (Bss and Bkss horizons).
Calcic horizon - zone from 30 to 38 inches (Bkss horizon).
MLRA: 271, 273.