LOCATION AGFAYAN GU+PBEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, isohyperthermic, shallow Udic Haplustolls
TYPICAL PEDON: Agfayan clay, on a 20 percent convex slope under a thick stand of swordgrass (Miscanthus floridulus). (Colors are for moist soil unless otherwise stated. Textures are apparent field textures.) When described, the soil was dry throughout.
A1--0 to 1 inch; black (10YR 2/1) clay, black (10YR 2/1) when dry; strong fine granular structure; hard, friable, very sticky and very plastic; many very fine and fine roots; many very fine and fine interstitial pores; cracks up to 0.5 inch wide exposed on the surface; slightly acid (pH 6.4); clear broken boundary. (0 to 2 inches thick).
A2--1 to 4 inches; black (10YR 2/1) clay, black (10YR 2/1) when dry; moderate coarse subangular blocky structure parting to strong fine subangular blocky; very hard, very firm, very sticky and very plastic; many very fine and fine roots; few very fine tubular pores within peds and many fine interstitial pores; cracks up to 0.5 inch wide between prisms; slightly acid (pH 6.4); clear smooth boundary. (3 to 6 inches thick)
A3--4 to 8 inches; black (10YR 2/1) clay, black (10YR 2/1) when dry; moderate coarse subangular blocky structure parting to moderate fine subangular blocky; very hard, very firm, very sticky and very plastic; many very fine and fine roots; many very fine and fine interstitial pores; few fine tubular pores; saprolitic pebbles content 15 percent that can easily be crushed to coarse sand and rubbed to sandy clay; cracks are less than 0.5 inch wide; neutral (pH 6.7); clear wavy boundary. (2 to 6 inches thick)
A/C--8 to 14 inches; mixed black (10YR 2/1) and yellowish brown (10YR 5/4) clay, black (10YR 2/1) and very pale brown (10YR 7/3) when dry; moderate fine subangular blocky structure; very hard, very firm, very sticky and very plastic; many very fine and fine roots; few thin clay films along fractures and pebble faces; saprolitic pebbles can be crushed to coarse sand and rubbed to sandy clay; slightly acid (pH 6.5); clear broken boundary. (0 to 8 inches thick)
Cr--14 inches; yellowish brown (10YR 5/4) weathered andesitic tuffaceous sandstone, very pale brown (10YR 7/3) when dry; can be dug with spade; occasional deep fractures which contain black and yellowish brown clay; many very fine roots; neutral (pH 6.9).
TYPE LOCATION: Guam; prominent south-facing roadcut along the east side of the road to the Ija Experiment Station, about 0.25 mile N. of main highway; lat. 13 degrees 15 minutes 10 seconds N. and long. 144 degrees 43 minutes 10 seconds E.
RANGE IN CHARACTERISTICS:
Soil moisture - Not continuously moist in all parts of the moisture control section for 90 to 120 cumulative days, primarily between February and May. Soil is usually moist from July through December.
Soil temperature - 80 to 86 degrees F., with less than 4 degrees F. variation between summer and winter.
Mollic Epipedon thickness - 4 to 10 inches.
Depth to paralithic contact - 4 to 15 inches.
Percent clay - Over 60 percent above the paralithic contact.
Coarse fragments - Commonly 10 to 20 percent but range from 2 to 30 percent, mostly as weathered pebbles. Unweathered pebbles and cobbles cover as much as 10 percent of the surface on steeper areas.
A horizon - Color: 10YR 2/1, 3/1, 3/2, 3/3, 2.5Y 3/2, 7.5YR 3/2. Texture: Clay.
Structure: Fine granular or subangular blocky.
Reaction: Slightly acid or neutral.
A/C horizon - Occurs in some pedons.
Bw horizon - Present in some pedons but not below 10 inches.
Color: 10YR 4/2, 4/3, 5/3, 5/4, 2.5Y 5/3, 6/3, and with 5YR 4/6, 4/8 colors on some ped faces.
Texture, structure: Similar to A horizon.
Reaction: Slightly acid or neutral.
C horizon - Present in some pedons below 7 inches.
Color: 10YR 5/4, 5/6, 6/6, 2.5YR 5/2, 6/2, 7/2, 5Y 4/3.
Structure: Massive, or rock structure.
Cr horizon - Color: 10YR, 2.5Y, and 5Y hues, commonly with values above 4.
Reaction: Commonly neutral. Some pedons have calcareous strata. Other features: In some pedons, an R horizon is below 40 inches.
COMPETING SERIES: None.
GEOGRAPHIC SETTING: Sloping to very steep uplands. Slopes range from 7 to 99 percent. The soils formed in marine-deposited tuff, tuff breccia and tuffaceous sandstones and shales. Elevation ranges from sea level to 1,080 feet. Mean annual precipitation is 80 to 100 inches, most of which falls between June and November. Mean annual temperature is 79 degrees F., with less than 4 degrees F. difference between summer and winter.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Akina, Atate, Pulantat, Sasalaguan, Togcha, and Ylig soils. Akina soils are moderately deep and have dominantly red hues in the B and Cr horizons. Atate and Togcha soils are deep. Pulantat soils have an argillic horizon. Sasalaguan soils are moderately deep and have an argillic horizon. Ylig soils are deep, are seasonally wet, and are in bottomland positions.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability; rapid runoff.
USE AND VEGETATION: This soil is used for wildlife habitat and as watershed. Vegetation is mainly savannah dominated by swordgrass (Miscanthus floridulus). In places, this soil is forested.
DISTRIBUTION AND EXTENT: Agfayan soils are in southern and central Guam and are moderately extensive, with a total of about 15,000 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Guam; July 1985.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - From the surface to the paralithic contact. Udorthentic subgroup - No secondary carbonates, and no cambic horizon.
ADDITIONAL DATA: This pedon was sampled and characterized by the National Soil Survey Laboratory (sample #S83-GU-066-002).