LOCATION UMIKOA HI

Established Series
Rev. RCH/HHS/AMS
02/2012

UMIKOA SERIES

The Umikoa series consists of deep, well drained soils that formed in basic volcanic ash over `a`a lava flows. Umikoa soils are on ash fields of mid elevation windward mountain slopes of Mauna Kea and have slopes of 0 to 20 percent. Mean annual rainfall is about 1397 millimeters (55 inches) and mean annual temperature is about 15 degrees C (59 degrees F).

TAXONOMIC CLASS: Medial, amorphic, isothermic Dystric Haplustands

TYPICAL PEDON: Umikoa medial silt loam on a 6 percent east facing slope under a cover of pasture at an elevation of 1260 meters (4140 feet). (Colors are for moist soil unless otherwise noted. When described, soil was moist throughout. All textures are apparent field textures.)

A--0 to 13 centimeters (0 to 5 inches); very dark brown (7.5YR 2/2) medial silt loam, dark brown (7.5YR 3/2), dry; weak fine subangular blocky structure parting to moderate fine granular; soft, very friable, slightly sticky, slightly plastic, weakly smeary; many fine roots throughout; many fine dendritic tubular pores; slightly acid (pH 6.2); abrupt wavy boundary. (8 to 20 centimeters {3 to 8 inches} thick)

Bw1--13 to 23 centimeters (5 to 9 inches); very dark brown (7.5YR 2.5/3) medial silt loam, dark brown (7.5YR 3/3), dry; weak fine subangular blocky structure parting to moderate fine granular; soft, very friable, slightly sticky, slightly plastic, weakly smeary; common fine roots throughout; common fine dendritic tubular pores; moderately acid (pH 6.0); abrupt wavy boundary. (10 to 20 centimeters {4 to 8 inches} thick)

Bw2--23 to 46 centimeters (9 to 18 inches); dark brown (7.5YR 3/4) medial silt loam, brown (7.5YR 4/4), dry; moderate fine subangular blocky structure; soft, very friable, slightly sticky, slightly plastic, weakly smeary; common fine roots throughout; many fine dendritic tubular pores; 5 percent subangular gravel and 2 percent subangular cobble sized `a`a lava fragments; slightly acid (pH 6.3); abrupt wavy boundary. (20 to 50 centimeters {8 to 20 inches} thick)

Bw3--46 to 91 centimeters (18 to 36 inches); very dark grayish brown (10YR 3/2) hydrous silty clay loam, dark grayish brown (10YR 4/2), dry; strong medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic, moderately smeary; few fine roots throughout; few fine dendritic tubular pores; moderately acid (pH 6.0); clear wavy boundary. (20 to 38 centimeters {8 to 15 inches} thick)

Bw4--91 to 127 centimeters (36 to 50 inches); dark brown (10YR 3/3) hydrous silty clay loam, dark yellowish brown (10YR 3/4), dry; strong medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic, moderately smeary; few fine roots throughout; few fine dendritic tubular pores; 5 percent subangular gravel and 5 percent subangular cobble sized `a`a lava fragments; moderately acid (pH 6.0); clear smooth boundary. (30 to 64 centimeters {12 to 25 inches} thick)

2C--127 centimeters (50 inches); fragmental `a`a lava.

TYPE LOCATION: Island of Hawaii, Hawaii County, Hawaii. Located about a mile south of Kukaiau Ranch headquarters, on north side of ranch road. Umikoa Quadrangle,19 degrees 58 minutes 4.3 seconds North latitude and 155 degrees 23 minutes, 10.9 seconds West longitude (Old Hawaiian Datum, +/- 12 feet, measured by Garmin GPS).

RANGE IN CHARACTERISTICS:
Soil moisture: The soil is typically dry in some or all parts for short intermittent periods totaling 90 or more days during the months of April through October in most years.
Soil temperature: 15 to 17 degrees C (59 to 63 degrees F).
Reaction: moderately to slightly acid (pH 5.6 to 6.5).
Depth to bedrock: 40 inches or greater.
Rock fragments: 0 to 10 percent on the surface and range from gravel to stone size `a`a lava rocks.

A horizon
Hue: 5YR to 10YR.
Value: 1 to 3.
Chroma: 1 to 3.
Texture: medial silt loam or very fine sandy loam.

2C horizon (occurs in some pedons, more common at higher elevations)
Hue: 2.5YR to 5YR.
Value: 3 to 5.
Chroma: 4 to 6.
Texture: ashy sandy loam or coarse sandy loam.
Fragments: 0 to 5 percent (by volume) gravel sized charcoal and cinder.

Bw horizons
Hue: 5YR to 10YR.
Value: 2 to 3.
Chroma: 2 to 4.
Texture: medial silt loam or very fine sandy loam; hydrous silty clay loam.
Fragments: 0 to 10 percent (by volume) gravel and cobble sized `a`a lava.

COMPETING SERIES: This is the Oli series. Oli soils are moderately deep and occur on the island of Molokai.

GEOGRAPHIC SETTING: The Umikoa soils are on mid elevation windward mountain slopes of Mauna Kea shield volcano at elevations from 1067 to 1524 meters (3500 to 5000 feet). The soils are on all hillslope profile positions of undulating ash fields that overlie 11,000 to 300,000 year old lava flows. Slope gradients range from 0 to 20 percent. The soils formed in basic volcanic ash. The mean annual rainfall is 1016 to 1524 millimeters (40 to 60 inches). Cloudiness and fog are prevalent throughout the year. Mean annual temperature is 14 to 16 degrees C (57 to 61 degrees F).

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Maile, Hanipoe, and Kemole soils. Maile soils occur at lower elevations and are typically moist throughout the profile and do not dry out for more than 90 cumulative days (udic soil moisture). Hanipoe soils occur at higher elevations and have mean annual soil temperature of 14 degrees C (57 degrees F) (isomesic soil temperature). Kemole soils are on narrow, rocky ridges that intersect Umikoa soils on 11,000 to 64,000 year old lava flows.

DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderately rapid permeability.

USE AND VEGETATION: These soils are used principally for pasture. The vegetation is dominated by kikuyugrass (Pennisetum clandestinum), rattailgrass (Sporobolus indicus), and sweet vernalgrass (Anthoxanthum odoratum) and Yorkshire fog (Holcus lanatus) at the higher elevations. Natural vegetation includes koa (Acacia koa), mamane (Sophora chrysophylla), ulei (Osteomeles anthyllidifolia), and naio (Myoporum sandwicense).

DISTRIBUTION AND EXTENT: This series occurs in the Hamakua and Mauna Kea districts on the island of Hawaii. It is moderately extensive, with a total of about 18,500 acres. MLRA 160: Subhumid and humid intermediate and high mountain slopes.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: County of Hawaii, Hawaii, 1960.

REMARKS:
Diagnostic horizons and features recognized in this pedon include:
Ustic soil moisture regime - dry in some or all parts for short intermittent periods totaling 90 or more days during the months of April through October in most years.
Isothermic soil temperature regime.
Ochric epipedon: 0 to 18 centimeters (0 to 7 inches).
Andic soil properties: 0 to 127 centimeters (0 to 50 inches).

06/2011: Updated taxonomy to reflect soil moisture and soil temperature updates.

National Cooperative Soil Survey
U.S.A.