LOCATION POZO BLANCO PREstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, isohyperthermic Aridic Calciustolls
TYPICAL PEDON: Pozo Blanco clay--Idle Land (Colors are for moist soil unless otherwise indicated).
Ap--0 to 7 inches; very dark grayish brown (10YR 3/2) clay; weak fine and medium subangular blocky structure; very hard, very firm; slightly sticky, very plastic; common fine roots; many very fine and fine irregular pores; about 12 percent, by volume, pebbles; few very fine masses of calcium carbonate concentrations; violently effervescent; moderately alkaline; clear smooth boundary. (7 to 10 inches thick)
Bw1--7 to 15 inches; very dark grayish brown (10YR 3/2) clay; strong fine and medium subangular blocky structure; very hard, very firm; slightly sticky, very plastic; common fine roots; common very fine and fine irregular pores, few very fine tubular pores; less than 5 percent, by volume, pebbles; few very fine masses of calcium carbonate concentrations; violently effervescent; moderately alkaline; clear smooth boundary.
Bw2--15 to 22 inches; dark brown (7.5YR 3/3) clay; strong fine and medium subangular blocky structure; hard, firm; slightly sticky, very plastic; few fine roots; common very fine and fine irregular pores, few very fine tubular pores; less than 5 percent, by volume, pebbles; few very fine and fine masses of calcium carbonate concentrations; violently effervescent; moderately alkaline; clear wavy boundary. (Combined thickness of Bw horizons range from 7 to 26 inches.)
Bk--22 to 30 inches; brown (7.5YR 4/3) gravelly clay loam; moderate fine subangular blocky structure; hard, firm; slightly sticky, moderately plastic; few fine roots; common very fine and fine irregular pores, few very fine tubular pores; common very fine and fine distinct very pale brown (10YR 7/3) masses of calcium carbonate concentrations; 20 percent, by volume, pebbles; violently effervescent; moderately alkaline; gradual wavy boundary. (5 to 23 inches thick)
C1--30 to 40 inches; dark yellowish brown (10YR 4/4) gravelly loam; massive; slightly hard, friable; slightly sticky, slightly plastic; few fine roots; common very fine irregular pores, few very fine tubular pores; about 20 percent, by volume, limestone pebbles; common fine faint very pale brown (10YR 7/3) concretions of calcium carbonate; violently effervescent; moderately alkaline; abrupt wavy boundary.
C2--40 to 60 inches; yellowish brown (10YR 5/4) loam; massive; soft, friable; slightly sticky, and slightly plastic; few fine roots; common very fine irregular pores, few very fine tubular pores; about 10 percent, by volume, limestone pebbles; common fine faint very pale brown (10YR 7/3) concretions of calcium carbonate; violently effervescent; moderately alkaline. (Combined thickness of C horizons ranges from 5 to 37 inches.)
TYPE LOCATION: Guanica, Puerto Rico. Approximately 1.1 miles east from the intersection of P.R. Hwy. 2 and P.R. Hwy. 332; about 800 feet northwest from the intersection of P.R. Hwy. 2 and P.R. Hwy. 116; about 400 feet northeast from dirt road on idle land. USGS Sabana Grande topographic quadrangle (1966); lat. 18 degrees 01 minute 01 second N.; long. 66 degrees 53 minutes 30 seconds W.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 24 to 42 inches. Reaction is slightly alkaline to moderately alkaline throughout. Concentration of masses of calcium carbonate range from none to few in the Ap and Bw horizons and from common to many in the Bk horizons. Concretions of calcium carbonate range from few to common in the C horizons.
The A or Ap horizon has hue of 7.5YR or 10YR, value of 3 or 4, and chroma of 1 or 2. Content of pebbles is less than 15 percent, by volume. Texture is clay.
The Bw horizon has hue of 7.5YR or 10YR, value of 3 or 4, and chroma of 2 to 4. Content of pebbles range from 5 to 20 percent, by volume. Texture is clay loam or clay in the fine-earth fraction.
The Bk horizon has hue of 7.5 YR or 10YR, value of 4 or 5, and chroma of 3 to 6. Content of pebbles range from 2 to 25 percent, by volume. Texture is clay loam, silty clay loam or clay in the fine-earth fraction.
The C horizon has hue of 10YR, value of 4 to 6, and chroma of 3 to 6. Content of pebbles range from 5 to 50 percent, by volume. Texture is sandy loam, loam or silty clay loam in the fine-earth fraction.
COMPETING SERIES: These are no known series in the same family. The closely related Aguilita series is in a coarse-loamy family and have a carbonatic mineralogy.
GEOGRAPHIC SETTING: Pozo Blanco soils are on alluvial fans and low hills of the Semiarid Mountains and Valleys MLRA. Slopes range from 0 to 20 percent. They formed in alluvium and colluvium over residuum derived from soft limestone. The climate is tropical semiarid. The average annual precipitation ranges from 25 to 66 inches and the average annual temperature ranges from 75 to 79 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aguilita, Cortada, Descalabrado, Duey, Fraternidad, Jacana, San Anton and San German series. Aguilita soils are in coarse-loamy family and have carbonatic mineralogy. Cortada, Fraternidad and San Anton soils are very deep on lower lying landscapes. In addition, Cortada and Fraternidad soils have smectitic mineralogy. Descalabrado soils are shallow to basic volcanic bedrock. Duey and San German soils are shallow to limestone bedrock. Jacana soils are moderately deep to basic volcanic bedrock and have vertic properties.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Most areas of Pozo Blanco soils are used for cash crops production. Some areas are used for hayland and pastureland. A few areas are on idle land. The vegetation consists of native and introduced grasses, shrubs and trees.
DISTRIBUTION AND EXTENT: Alluvial fans and low hills of the semiarid mountains and valleys of southern Puerto Rico. The series is small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: Soil Survey of Puerto Rico; 1942.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - the zone from 0 to 22 inches (Ap, Bw1 and Bw2 horizons).
Cambic horizon - the zone from 7 to 22 inches (Bw1 and Bw2 horizons).
Calcic horizon - the zone from 22 to 30 inches (Bk horizon).
The type location was moved to its present location because the type location selected on 1998 was updated to be an Aridic Soil Moisture Regime based on a soil moisture study in southern Puerto Rico. The concept of the Pozo Blanco soils is on Ustic Soil Moisture Regime.
Pozo Blanco soils are in MLRA 271.