LOCATION POHAKUPU                HI

Established Series
Rev. HHS/SN/MRK
03/2017

POHAKUPU SERIES

The Pohakupu series consists of deep, well drained soils that formed in alluvium from basic volcanic rock. Pohakupu soils are on alluvial fans and terraces and have slopes of 0 to 15 percent. Mean annual rainfall is about 1270 millimeters (50 inches) and the mean annual temperature is about 23 degrees C. (73 degrees F.)

TAXONOMIC CLASS: Fine, parasesquic, isohyperthermic Oxic Humustepts

TYPICAL PEDON: Pohakupu silty clay loam - pasture. (Colors are for moist soil unless otherwise noted. All textures are "apparent field textures.")

Ap--0 to 33 centimeters (0 to 13 inches); dark reddish brown (5YR 3/3) silty clay loam, reddish brown (5YR 4/3) dry; strong very fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; many fine roots; many very fine and fine interstitial pores; common worm holes and casts; slight effervescence with hydrogen peroxide; slightly acid (pH 6.1); abrupt smooth boundary. (20 to 33 centimeters {8 to 13 inches} thick)

Bw1--33 to 53 centimeters (13 to 21 inches); dark reddish brown (5YR 3/3) silty clay loam, reddish brown (5YR 4/4) dry; moderate very fine subangular blocky structure; hard, friable, slightly sticky and moderately plastic; many very fine roots; many very fine and fine tubular pores; common patchy pressure faces; slight effervescence with hydrogen peroxide; slightly acid (pH 6.2); abrupt smooth boundary. (10 to 23 centimeters {4 to 9 inches} thick)

Bw2--53 to 97 centimeters (21 to 38 inches); dark brown (7.5YR 3/4) silty clay loam, brown (7.5YR 4/4) dry; strong very fine angular and subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; many very fine and fine tubular pores; continuous pressure faces; many black stains in pores and on peds that have strong effervescence with hydrogen peroxide; 2 percent gravel; slightly acid (pH 6.4); clear irregular boundary. (10 to 46 centimeters {4 to 18 inches} thick)

Bw3--97 to 127 centimeters (38 to 50 inches); dark brown (7.5YR 3/4) silty clay loam, brown (7.5YR 4/4) dry; strong very fine angular and subangular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine roots; many very fine and fine tubular pores; strong continuous pressure faces; common black stains that very slight effervesce with hydrogen peroxide; 2 percent gravel; slightly acid (pH 6.2); clear irregular boundary. (28 to 51 centimeters {11 to 20 inches} thick)

Bw4--127 to 193 centimeters (50 to 76 inches); dark brown (7.5YR 3/4) silty clay loam, brown (7.5YR 4/4) dry; strong very fine angular and subangular blocky structure; hard, friable, slightly sticky and moderately plastic; few very fine roots; many very fine and fine tubular pores; nearly continuous faces; few fine black stains that very slight effervesce with hydrogen peroxide; 2 percent gravel; slightly acid (pH 6.2).

TYPE LOCATION: Island of Oahu, Honolulu County, Hawaii; latitude 21 degrees 22 minutes 53 seconds North and longitude 157 degrees 45 minutes 16 seconds West (WGS84); at the intersection of Kalanianaole Highway and Kailua Road; turn toward Waimanalo, proceed 1,800 feet to Ulupii Street; pedon is 50 feet west of highway on Waimanalo side of Ulupii Street.

RANGE IN CHARACTERISTICS: Effervescence with hydrogen peroxide ranges from slight to moderate in the upper part of the solum and slight to none below. An occasional boulder core occurs within the lower part of the profile in some pedons. Mean annual soil temperature is about 73 degrees F.

The A horizon has value and chroma of 2 or 3 moist.

The Bw horizon has hue of 7.5YR or 5YR, and value and chroma of 3 or 4 moist. The B horizon has moderate or strong structure.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Pohakupu soils are on alluvial fans and terraces at elevations of 15 to 76 meters (50 to 250 feet). Slope is 0 to 15 percent. The soils formed in alluvium from basic volcanic rock. Annual rainfall is 1,016 to 2,032 millimeters (40 to 80 inches). Average January temperature is about 22 degrees C. (71 degrees F.); average July temperature is about 25 degrees C. (77 degrees F.); mean annual temperature is about 23 degrees C. (73 degrees F.)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alaeloa and Papaa soils. Alaeloa soils have an argillic horizon with thick continuous clay films in the lower part and are strongly acid throughout the B horizon. Papaa soils are Vertisols and have a clay control section.

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

USE AND VEGETATION: Used for pasture, truck crops and urban development. Vegetation is guava (Psidium guajava), Christmasberry (Schinus terebinthifolius), Japanese tea (Cassia leschenaultiana), koa-haole (Leucaena glauca), bermudagrass (Cynodon dactylon) and hilograss (Paspalum conjugatum).

DISTRIBUTION AND EXTENT: Islands of Oahu and Kauai, Hawaii. This series is inextensive, comprising about 1,500 acres.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Davis, California

SERIES ESTABLISHED: Island of Oahu, Honolulu County, Hawaii, 1971.

REMARKS:
Diagnostic horizons and features recognized in this pedon include:
Ustic soil moisture regime
Umbric epipedon from 0 to 33 centimeters
Cambic horizon from 33 to 193 centimeters
Reclassified using the 12th edition of Keys to Taxonomy.

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National Cooperative Soil Survey
U.S.A.