LOCATION IAO HI

Established Series
Rev. SN/JVP/MRK
09/2019

IAO SERIES

The Iao series consists of deep, well drained soils that formed in alluvium weathered from basic igneous rock. Iao soils are on valley floors and alluvial fans. Slopes range from 0 to 15 percent. The mean annual precipitation is about 838 millimeters (33 inches) and the mean annual air temperature is about 24 degrees C. (75 degrees F.).

TAXONOMIC CLASS: Fine, mixed, active, isohyperthermic Cumulic Haplustolls

TYPICAL PEDON: Iao clay - sugarcane. (Colors are for moist soil unless otherwise noted. All textures are "apparent field textures.")

Ap--0 to 38 centimeters (0 to 15 inches); dark brown (10YR 3/3) clay, dark gray (10YR 4/1) dry; massive due to tillage; very hard, firm, very sticky and very plastic; many roots; many fine pores; few cracks up to 1/4 inch wide; many weathered sand grains of basalt; strong effervescence with hydrogen peroxide; neutral (pH 7.0); gradual smooth boundary. (31 to 46 centimeters thick)

Bw1--38 to 64 centimeters (15 to 25 inches); very dark brown (10YR 2/2) clay, very dark grayish brown (10YR 3/2) when rubbed, dark brown (10YR 3/3) dry; weak medium and coarse subangular blocky structure; very hard, firm, very sticky and very plastic; very hard, firm; many roots; many very fine pores; many weathered sand grains of basalt; few basalt pebbles; strong effervescence with hydrogen peroxide; neutral (7.1); gradual smooth boundary. (20 to 27 centimeters thick)

Bw2--64 to 122 centimeters (25 to 48 inches); dark brown (10YR 3/3), moist and dry, clay; moderate medium and coarse subangular blocky structure; very hard, firm, very sticky and very plastic; compact in place; few fine roots; many fine pores; pressure faces on all face of peds; strong effervescence with hydrogen peroxide; neutral (pH 6.8); gradual smooth boundary. (51 to 69 centimeters thick)

BC--122 to 152 centimeters (48 to 60 inches); very dark grayish brown (10YR 3/2) silty clay, dark brown (10YR 3/3) dry; massive; hard, firm, moderately sticky and moderately plastic; few roots; many fine and medium pores; many weathered sand grains and pebbles of basalt; strong effervescence with hydrogen peroxide; neutral (pH 6.8).

TYPE LOCATION: Island of Maui, Maui County, Hawaii; about 1.2 miles northwest of Wailuku Post Office, 100 feet west of Kahekili Highway and 100 feet north of plantation road in field No. 41, Wailuku Sugar Company. Wailuku Quadrangle; latitude 20 degrees 54 minutes 5.33 seconds N. and longitude 156 degrees 30 minutes 30.20 seconds W. (WGS 84)

RANGE IN CHARACTERISTICS: Thickness of the solum is more than 102 centimeters (40 inches). In some places, a few cobblestones are in the surface layer. The mean annual soil temperature is about 23 degrees C. (74 degrees F.).

The A horizon has color value of 2 or 3 moist or 3 or 4 dry, and chroma of 1 through 3 moist and 1 or 2 dry. Texture ranges from silty clay to clay. It may have weak subangular structure.

The B horizon has color value of 2 or 3 moist or 4 dry, and chroma of 2 or moist or dry. Texture ranges from silty clay to clay. It can have medium and coarse subangular blocky structure.

The BC horizon, when present, has color value of 2 or 3 moist or 4 dry, and chroma of 2 or moist or dry. Texture ranges from silty clay to clay.

COMPETING SERIES: This is the Haleiwa series. Haleiwa soils have silty clay textures throughout.

GEOGRAPHIC SETTING: Iao soils are on valley floors and alluvial fans at elevations of 10 to 199 meters (33 to 653 feet). Slopes are 0 to 15 percent. The soils formed in alluvium from basic igneous rock. The mean annual precipitation ranges from 635 to 1279 millimeters (25 to 50 inches). The mean annual air temperature is about 24 degrees C. (75 degrees F.); the average January temperature is 23 degrees C. (72 degrees F.); and the average July temperature is 26 degrees C. (78 degrees F.).

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Paia, Pulehu and Wailuku soils. Paia soils have a very- fine control section. Pulehu soils have a fine- loamy control section. Wailuku soils are slightly to moderately acid and have a semi- active cation exchange activity class.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: The soils are well drained. Runoff is low to medium. Saturated hydraulic conductivity is moderately high.

USE AND VEGETATION: These soils are used for irrigated sugarcane. The natural vegetation is bermudagrass (Cynodon dactylon), feather fingergrass (Chloris virgata), koa hoale (Leucaena glauca), lantana (Lantana camara), and Natal redtop (Melinis repens).

DISTRIBUTION AND EXTENT: Island of Maui, Maui County, Hawaii. MLRA 158 - Semiarid and Subhumid Low Mountain Slopes; and MLRA 163 - Alluvial Fans and Coastal Plains. This series is about 3,346 acres in extent. These soils are not extensive.

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

SERIES ESTABLISHED: Island of Maui, Maui County, Hawaii, 1949.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon- the zone from a depth of 0 to 122 centimeter (Ap, Bw1, and Bw2).
Cambic horizon - the zone from a depth of 38 to 122 centimeters (Bw1 and Bw2).

National Cooperative Soil Survey
U.S.A.