LOCATION ODESANGEL               PW+FM PB

Established Series
RD: JLN/RTG/AJT
04/2026

ODESANGEL SERIES

The Odesangel series consists of very deep, very poorly drained soils on anthropogenic artificial fens, solution sinkholes, depressions, and swamps areas of atolls and karst islands that retain fresh or brackish water. These soils formed in deposits of organic material derived predominantly from freshwater marsh vegetation overlying coralline sand. Slope is 0 to 1 percent. The mean annual rainfall is about 3685 millimeters (145 inches), and the mean annual air temperature is about 27 degrees C (81 degrees F).

TAXONOMIC CLASS: Sandy or sandy-skeletal, carbonatic, euic, isohyperthermic Terric Haplohemists

TYPICAL PEDON: Odesangel mucky peat in a 1 percent slope area supporting wetland taro and limestone-swamp forest plant communities at an elevation of 5 meters. (Colors are for moist soil. All textures are apparent field textures. When described on February 6, 1980, the soil was saturated throughout and the water table was at 20 centimeters (8 inches) below the surface.)

Oe1--0 to 8 centimeters (0 to 3 inches); dark brown (7.5YR 3/2) mucky peat ; 80 percent fiber, 20 percent rubbed; massive; nonsticky and nonplastic; many very fine, fine and medium and few coarse roots; color is 7.5YR 7/4 in pyrophosphate solution; neutral (pH 6.8 ); clear wavy boundary. Lab sample # 80P01023

Oe2--8 to 53 centimeters (3 to 21 inches); dark brown (7.5YR 3/2) mucky peat ; about 70 percent fiber; 22 percent rubbed; massive; nonsticky and nonplastic; common very fine and fine roots and medium roots; color is 7.5YR 7/4 in pyrophosphate solution; neutral (pH 6.8); clear smooth boundary. (Combined thickness of the Oe horizons is 45 to 75 centimeters [18 to 30 inches].) Lab sample # 80P01024

2C--53 to 150 centimeters (21 to 59 inches); pale brown (10YR 6/3) coarse sand; single grain; loose; nonsticky; nonplastic; few very fine and fine roots; many very fine interstitial pores; moderately alkaline (pH 8.0). (75 to 105 centimeters [30 to 40 inches] thick.)

TYPE LOCATION: Peleliu Municipality and Island, Republic of Palau, about 1.9 kilometers (0.99 miles) south-southwest of the school yard at Peleliu Village on the main road and then about 94 meters (308 feet) northwest of the roadway at the edge of the taro patch; WGS 84 UTM 417284 meters E, 777060 meters N, zone 53; Lat 7 1' 45.64.08" N and Long 134 15' 3.91" E.

RANGE IN CHARACTERISTICS :
Soil moisture: The soils have an aquic soil moisture regime. The soil is saturated in some part throughout the year, with a seasonal high water table fluctuating between 0 and 25 centimeters (0 to 10 inches). The soil moisture subclass is oxyaquic.

Seasonal pattern: Rainfall averages about 3685 millimeters (145 inches) per year and ranges from approximately 2900 to 4400 millimeters (114 to 173 inches) There are two seasons: wet (May to November) and dry (December to April). The driest months (February, March, and April) average 180 to 230 milliliters (7 to 9 inches) per month. The soils are flooded daily with ocean salt water during periods of high tide.

Diagnostic Features:
Depth to lithologic discontinuity: 40 to 60 centimeters (16 to 24 inches)
Hemic soil materials: 0 to 75 centimeters (0 to 30 inches)
Aquic conditions : 0 to 200 centimeters (0 to 80 inches)
Linear extensibility: 0 to 1 percent weighted average, RV is 0.5 percent

Oa, Oe, or Oi horizon(s):
Hue: 7.5YR or 10YR
Value: 2 to 4 moist
Chroma: 1 to 3 moist
Texture: muck, mucky peat, peat
Silt content: 0 to 15 percent
Clay content: 0 to 15 percent
Carbonate clay content: 0 to 1 percent
Sand content: 70 to 100 percent
Calcium carbonate equivalent: 0 to 5 percent
Electrical conductivity: 0 to 3 mmhos/cm
Reaction: ultra acid to neutral (pH 3.0 to 7.3)
Cation exchange capacity: 140 to 160 meq/100grams
Organic matter content: 60 to 100 percent

2C horizons
Hue: 10YR or 2.5Y
Value: 6 to 8 moist
Chroma: 1 to 4 moist
Texture: coarse sand, sand or mucky sand
Rock fragments: 0 to 50 percent coralline limestone gravel
Silt content: 0 to 10 percent
Clay content: 0 to 8 percent
Carbonate clay content: 0 to 1 percent
Sand content: 85 to 100 percent
Calcium carbonate equivalent: 85 to 95 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: neutral to moderately alkaline (pH 6.6 to 8.4)
Cation exchange capacity: 0 to 5 meq/100grams
Organic matter content: 0.5 to 1.5 percent

COMPETING SERIES: There are no other series in this family at this time.

GEOGRAPHIC SETTING: Odesangel soils are on anthropogenic artificial fens, solution sinkholes, depressions, and swamps areas of atolls and karst islands that retain fresh or brackish water. Slope is 0 to 1 percent. These soils formed in organic material derived predominantly from freshwater marsh vegetation overlying coralline sand. Elevation is 0 to 25 meters (0 to 82 feet.) The water table ranges from the surface to 25 centimeters (10 inches) below the surface. The climate is tropical and moist. Because of the strong marine influence, the diurnal and annual range of temperature is limited. Rainfall averages about 3685 millimeters (145 inches) per year and ranges from approximately 2900 to 4400 mm (114 to 173 in.) There are two seasons: wet ( May to November) and dry (December to April). The driest months (February, March, and April) average 180 to 230 milliliters (7 to 9 inches) per month. Rainfall is derived from convective uplift, which results in short duration rainstorms of high intensity. Rainfall is irregularly distributed geographically. The mean daily temperature throughout the year averages 27 C (81 F) with a mean diurnal range of about 4 C (7 F.) Relative humidity averages about 90 percent at night and 75 to 80 percent during the day.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chelbacheb, Majuro, Ngedebus, and Peleliu soils. Chelbacheb soils are shallow, well drained soils on karst islands. They formed in organic material over coralline limestone in slightly convex areas at the base of jagged coral limestone rock outcrops. Ngedebus and Majuro soils are very deep, somewhat excessively drained soils generally adjacent to coastal beaches. These soils formed in water and wind-deposited coral rubble and sand. Ngedebus soils are typically found on the lagoon sides of atolls whereas Majuro soils are typically found on the ocean sides of atolls and have greater than 35 percent rock fragments in the subsoil. Peleliu soils are shallow, well drained soils on karst islands. The soils formed in residuum derived dominantly from limestone. Typically, more than 50 percent of the soil surface is covered with gravel, cobbles, and stones. The soil matrix is very gravelly with 25 to 50 percent gravel and 15 to 35 percent cobbles. Permeability is rapid in the soil material and underlying limestone bedrock

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Very poorly drained. Negligible runoff. Saturated hydraulic conductivity is very high in the organic material and high in the underlying material. A fluctuating water table ranges from 0 to 25 centimeters (0 to 10 inches) below the surface. The soils are ponded frequently for very long periods all months of the year.

USE AND VEGETATION: These soils are in limestone marshes and swamp forest plant communities and are used mainly for the production of wetland taro. The dominant taro species are Giant Swamp Taro (Cyrtosperma merkusii or Brak in Palaun) and wetland taro (Colocasia esculenta or Kukau in Palaun). The swamp forest is dominated by a variety of native species, including powder puff tree (Barringtonia racemosa) and sea hibiscus (Hibiscus tiliaceus ). Swamp forests tend to be closed-canopied containing few tree species. The marshes are dominated with tall reed (Phragmites karka), although much has been converted to taro.

DISTRIBUTION AND EXTENT: MLRA 194 - Volcanic Islands of Western Micronesia, Republic of Palau, MLRA 195 - Volcanic Islands of Central and Eastern Micronesia, and MLRA 196 - Coral Atolls of Micronesia. The soils of this series are of small extent; about 1000 acres in size. They are mapped on the islands of Angaur, Babeldaob, Kayangel, Ngerechong, Peleliu, Pula Ana, Sonsorol, and Tobi Islands; Republic of Palau; the islands in the Republic of the Marshall Islands, and the islands of Pohnpei, Kosrae and the Chuck Islands; Federated States of Micronesia.

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

SERIES PROPOSED: Island and Municipality of Peleliu, Republic of Palau, 2007. Local pronunciation of the word Odesangel is "O-des-angle." Its name is derived from the old name for Peleliu back in the 1600s.

REMARKS: Lab analyses of the Odesangel series on Peleliu showed lower soil organic matter than usual for this series. The samples were collected from sites that have been used for cultivating taro for hundreds of years. Odesangel soils generally contain about 80 percent organic matter. The karst topography contains common features including pits and pinnacles, caves, depressions, and sinkholes. Depressional areas are often associated with phosphate-mine areas. The depressions consist of fresh and brackish waters located in the interior of the islands. The traditional system of agriculture included intensive taro cultivation. The soil is first dug to the freshwater lens, then tall grasses and sedges, weeds, and young trees are removed or pushed into the mud as fertilizer. The soil is turned over and worked, which requires the Palauans to dig down deep as far as they can with their hands and lift the mud and organic matter to turn it over. Wood ashes, twigs, grasses, and leaves are added below the mud to keep insects, fungus, and bacteria away and for fertilizer.

Atolls are ring shaped islands, formed from coral reefs building around a volcanic island. As the volcano subsides, the coral reef is left behind, forming the iconic rings. Where the volcano once was is a shallow "lagoon", a salty protected body of water that is tidally connected to the ocean. In some cases it is open to the ocean, but because of the reef, the inside of the island is more protected from the open sea.

There are no surface-flowing rivers on the islands where these soils occur, though brief periods of storm flow may occur. Rainfall rapidly infiltrates the limestone or coral sand parent materials until it reaches an impediment or the denser salt water. A thin Ghyben-Herzberg freshwater lens exists under the limestone soils. In the low plain section of Peleliu and in sandy areas near the shore, ground water is obtained through wells to the freshwater lens. On Angaur, the thin Ghyben-Herzberg freshwater lens exists under the southeastern part of the island within the coral rubble and calcareous sand. Potable water is obtained from wells and rain catchment systems.

Diagnostic horizons and features recognized in this pedon are:
Hemic materials - 0 to 53 centimeters (0 to 21 inches) (Oe horizon)
Aquic conditions - 0 to 150 centimeters (0 to 59 inches)
Lithologic discontinuity - 53 centimeters (21 inches) (C horizon)
Particle-size control section - 0 to 130 centimeters (0 to 51 inches)

ADDITIONAL DATA: National Soil Survey Laboratory Pedon # 80P0200 and Military Geology of Palau Islands, 1956, are used to define the series. Additional data are National Soil Survey Laboratory Pedon # 81P0020 (Ngerungor Series) and Nutrient Content of Odesangel Soils, Island of Peleliu; Sample number: S1, S2, S7, S13; pH: 5.2, 6.6, 6.3, 7.5; Organic Matter (%): 45, 30, 13, 16; Nitrogen (%): 2.1, 1.4, 0.5, 0.1 ; Phosphorus (ppm): 12, 22, 74, 35; Potassium (ppm): 68, 118, 8,25; Calcium (ppm): 3050, 6023, 3889, 7409; Magnesium (ppm):670, 75, 37, 329; Zinc (ppm):16,48; Iron (ppm):123, 109; Manganese (ppm): 3, 20 .

Soil classified using the Keys to Soil Taxonomy, 13th edition 2022.

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National Cooperative Soil Survey
U.S.A.