LOCATION VEGA ALTA PREstablished Series
TAXONOMIC CLASS: Fine, parasesquic, isohyperthermic Typic Hapludults
TYPICAL PEDON: Vega Alta clay loam--marker grass. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; dark yellowish brown (10YR 3/4) clay loam; moderate fine granular structure; friable; slightly sticky, slightly plastic; common fine roots; many fine black (10YR 2/1) manganese concretions; strongly acid; abrupt wavy boundary. (6 to 10 inches thick)
Bt1--8 to 14 inches; 50 percent reddish yellow (7.5YR 6/8) and 50 percent yellowish red (5YR 4/6) clay; weak medium and coarse subangular blocky breaking to moderate fine granular; firm; slightly sticky, slightly plastic; few fine roots; few faint clay films on surfaces of peds and root channels; many fine black (10YR 2/1) manganese concretions; strongly acid; clear wavy boundary.
Bt2--14 to 25 inches; 50 percent red (2.5YR 4/8) and 50 percent strong brown (7.5YR 5/8) clay; moderate medium and coarse subangular blocky breaking to weak medium blocky; firm; slightly sticky, slightly plastic; few fine roots; common prominent clay films on faces of peds and root channels; few fine black (10YR 2/1) manganese concretions; strongly acid; gradual wavy boundary.
Bt3--25 to 36 inches; 50 percent red (2.5YR 4/8) and 50 percent brownish yellow (10YR 6/8) clay; weak medium and coarse subangular blocky structure; firm; nonsticky, slightly plastic; common distinct brownish yellow (10YR 6/6) clay films on faces of peds and in root channels; few fine quartz grains; very strongly acid; gradual wavy boundary.
Bt4--36 to 52 inches; 33 percent dark red (10R 3/6), 33 percent red (7.5R 5/8), and 34 percent light gray (5Y 7/1) clay; weak coarse subangular blocky structure; friable; nonsticky, slightly plastic; few faint clay films on faces of peds; the areas of dark red and strong brown are iron accumulations and the areas of light gray are iron depletions; very strongly acid; gradual wavy boundary. (Thickness of the Bt horizons range from 37 to 55 inches)
C--52 to 84 inches; 33 percent dark red (10R 3/6), 33 percent brownish yellow (10YR 6/8), and 34 percent light gray (5Y 7/1) clay; massive; friable; nonsticky, slightly plastic; the areas of dark red and brownish yellow are iron accumulations and the areas of light gray are iron depletions; very strongly acid.
TYPE LOCATION: San Juan SCD, Puerto Rico. Rio Piedras Experiment Station on the section of farm north of P.R. Highway 1 to Caguas, about 150 feet north of radio station, about 50 feet south of trail, and east of Rum Pilot Plant.
RANGE IN CHARACTERISTICS: Thickness of solum ranges from 43 to 65 inches and that of the Bt horizons from 37 to 55. Base saturation (by sum of cations) is less than 35 percent at 50 inches below the top of the argillic horizon. Exchange capacity in the major part of the argillic is between 16 and 24 meq. per 100 grams of clay. Organic matter content is 0.8 percent or less in the upper 6 inches of the argillic horizon.
The A or Ap horizon has hue of 7.5YR or 10YR, value of 3 or 4, and chroma of 3 or 4. Where the value is 3, it is less than 8 inches in thickness. Texture is clay loam or silty clay.
The upper part of the Bt horizon has hue of 2.5YR to 7.5YR, value of 4 to 8, and chroma of 3 to 6; or it is multicolored in shades of red and yellow. Iron accumulations in shades of yellow and red range from none to common. The lower part of the Bt horizon has hue of 10R to 5YR, value of 5 to 8, and chroma of 3 to 6; or it is multicolored in shades of red, brown, or yellow. Iron accumulations in shades of yellow, brown, or red range from none to common. Iron depletions in shades of gray occur below a depth of 30 inches and range from few to many. Soft masses of manganese range from few to many throughout. Texture is clay loam or clay.
The C horizon has no dominant color and is multicolored in shades of red, yellow, brown, and gray. Soft masses of manganese range from few to many. Texture is clay.
COMPETING SERIES: These are no known series in the same family.
GEOGRAPHIC SETTING: Vega Alta soils are on uplands and terraces. Slopes range from 2 to 12 percent. They formed in fine textured, iron rich coastal plain sediments. The climate is humid tropical. The average annual precipitation ranges from 72 to 80 inches and the average annual temperature ranges from 76 to 78 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Bajura, Coloso, Rio Piedras, Toa, and Vega Baja soils. The Bajura, Coloso, and Toa soils are on lower flood plain positions. In addition, Bajura soils are poorly drained and are Mollisols, Coloso soils are somewhat poorly drained, and Toa soils are Mollisols. The moderately well drained Rio Piedras soils are on similar positions but are underlain by highly weathered, thinly bedded siltstone and are Mollisols. The somewhat poorly drained Vega Baja soils are on slightly lower terrace positions and have higher exchange capacity.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Most areas of Vega Alta soils are used for the production of sugarcane and for pasture. The vegetation consists of native and introduced grasses, shrubs, and trees.
DISTRIBUTION AND EXTENT: Humid northern coastal plains of Puerto Rico. This series is of limited known extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: Soil Survey of Puerto Rico; l942.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Ochric epipedon - the zone from 0 to 8 inches (Ap horizon).
Argillic horizon - the zone from 8 to 52 inches (Bt1, Bt2, Bt3, and Bt4 horizons).
This draft reflects a change in classification from: Fine, kaolinitic, isohyperthermic Typic Hapludults to: Fine, parasesquic, isohyperthermic Typic Hapludults.
These data support the change in classification. Other data show that these soils have 10 percent or more weatherable minerals in the 20 to 200 micron fraction of the upper 40 inches.
ADDITIONAL DATA: Characterization pedon - San Juan SCD, Puerto Rico; S61PR127-002. Sample by NSSL, Lincoln, NE.