LOCATION OFU AS+PBEstablished Series
TAXONOMIC CLASS: Very-fine, ferruginous, isohyperthermic Typic Acroperox
TYPICAL PEDON: Ofu silty clay - on a 19 percent convex slope in a banana and coconut plantation. When described the soil was moist throughout. (Colors are for moist soil unless otherwise stated. Textures are apparent field textures.)
Ap--0 to 16 inches; dark reddish brown (5YR 3/3) silty clay, dark reddish brown (5YR 3/3) dry; strong medium and fine subangular blocky structure; very hard, friable, very sticky and very plastic; common very fine and fine and few medium roots; common very fine and fine pores; neutral (pH 6.9); clear smooth boundary. (8 to 17 inches thick).
Bw1--16 to 31 inches; dark brown (7.5YR 4/3) silty clay loam, dark reddish brown (5YR 3/4) dry; moderate medium subangular blocky structure; very hard, friable, sticky and plastic; few very fine and fine roots; many very fine and fine pores; neutral (pH 6.8); gradual smooth boundary. (8 to 15 inches thick)
Bw2--31 to 45 inches; dark brown (7.5YR 4/4) silty clay loam, dark reddish brown (5YR 3/3) dry; moderate medium subangular blocky structure; very hard, friable, sticky and plastic; few very fine and fine roots; many very fine and fine pores; neutral (pH 6.8); clear smooth boundary. (8 to 16 inches thick).
Bw3--45 to 60 inches; dark brown (7.5YR 4/4) silty clay, dark reddish brown (5YR 3/4) dry; moderate medium subangular blocky structure; firm, very sticky and very plastic; few fine roots; common very fine and fine pores; neutral (pH 6.9).
TYPE LOCATION: Ofu Island, American Samoa; near Alaufau about 1/4 mile east northeast of village; lat. 14 degrees 10 minutes 13 seconds S. and long. 169 degrees 40 minutes 34 seconds W.
RANGE IN CHARACTERISTICS: The solum is 24 to 60 inches thick. The profile is 0 to 10 percent cobbles and 0 to 10 percent pebbles. It is medium acid to neutral.
The A horizon has hue of 5YR or 7.5YR, value of 2 or 3, and chroma of 2 or 3 moist or dry.
The upper part of the B horizon has a hue of 5YR or 7.5YR and the lower part 2.5YR through 10YR; value is 3 or 4, and chroma is 3 through 6 moist or dry. It is silty clay or silty clay loam.
The C horizon where present has hue of 2.5YR through 7.5YR, value of 3 or 4, and chroma of 3 through 6 moist or dry. Texture is clay loam or silty clay loam.
COMPETING SERIES: This is the Fagasa series. Fagasa soils have a paralithic contact at a depth of 20 to 40 inches.
GEOGRAPHIC SETTING: Ofu soils are on moderately steep to very steep mountainsides. Slope is 15 to 70 percent. These soils formed in volcanic ash and residuum from basic igneous rock. Elevation is 50 to 1500 feet. The mean annual rainfall is 150 to 225 inches, and the mean annual temperature is 77 to 80 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Fagasa soils.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Ofu soils are used for subsistence farming. Undisturbed areas are in tropical forest that provide a source of firewood and timber.
DISTRIBUTION AND EXTENT: Islands of Ofu, Olosega, and Tutuila. The soils of this series are of small extent, about 2200 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: American Samoa, 1982.
ADDITIONAL DATA: This pedon number S81 AQ602-065 was sampled and analysis was performed by the SCS National Soil Survey Lab in 1981.