LOCATION MAJURO MH+PB PW

Established Series
HHS/JLN/RTG
07/2022

MAJURO SERIES

The Majuro series consists of very deep, somewhat excessively drained soils derived from water- and wind-deposited coralline rubble and sand. These soils are on beach ridges, beach terraces, and beaches, of atolls, karsts, and islands, generally on the oceanside of islands. Saturated hydraulic conductivity is high in the subsoil and in the underlying material. Slope is 0 to 6 percent. The average annual rainfall is about 3,500 millimeters (138 inches), while the dry, northern atolls may only average 508 millimeters (20 inches.) and the average annual temperature is about 27 C (81 F).

TAXONOMIC CLASS: Sandy-skeletal, carbonatic, isohyperthermic Typic Udorthents

TYPICAL PEDON: Majuro very cobbly loamy sand southeast facing, linear, 1 percent in a casuarina and atoll-forest plant community at an elevation of 1 meter (3.3 feet.) The surface is covered by about 15 percent gravel, and 60 percent cobbles. The fragments are coralline limestone. About 5 percent is bare ground. (Colors are for moist soil unless otherwise noted. All textures are apparent field textures. When described on April 1, 1979, the soil was moist throughout.)

A--0 to 15 centimeters (0 to 6 inches); grayish brown (10YR 5/2) very cobbly loamy sand; weak medium angular blocky structure; very friable, nonsticky and nonplastic; common fine and medium roots; many fine interstitial pores; strongly effervescent; rock fragments are coralline limestone; 10 percent gravel, 30 percent cobbles; moderately alkaline (pH 8.0); abrupt wavy boundary. (10 to 25 cm thick)

AC--15 to 32 centimeters (6 to 13 inches); pale brown (10YR 6/3) very cobbly loamy sand; single grain; loose, nonsticky and nonplastic; common fine and medium roots; many fine interstitial pores; strongly effervescent; rock fragments are coralline limestone; 10 percent gravel, 30 percent cobbles; moderately alkaline (pH 8.0); gradual wavy boundary. (10 to 20 centimeters thick)

C1--32 to 62 centimeters (13 to 24 inches); very pale brown (10YR 7/3) very cobbly sand; single grain; loose, nonsticky and nonplastic; few fine and medium roots; many fine interstitial pores; strongly effervescent; rock fragments are coralline limestone; 15 percent gravel, 40 percent cobbles; moderately alkaline (pH8.2); gradual smooth boundary. (20 to 50 centimeters thick)

C2--62 to 200 centimeters (24 to 79 inches); very pale brown (10YR 8/3) very gravelly sand; single grain; loose, nonsticky and nonplastic; many fine interstitial pores, strongly effervescent; rock fragments are coralline limestone; 10 percent gravel, 30 percent cobbles; moderately alkaline (pH 8.2).

TYPE LOCATION: Mili Island, Mili Atoll in the Republic of the Marshall Islands; about 1,295 meters (4250 feet) south of the northern tip of Mili Island and 24 meters (80 feet) east of the oceanside; WGS 84 UTM 4868342 meters E, 839763 meters N, zone 59; Lat 7 25' 55" N and Long 151 51' 50.5" E. latitude 6 5' 30" N. and longitude 171 43' 45" E.

RANGE IN CHARACTERISTICS:
Soil moisture:
Soil moisture regime subclass: typic
Soil moisture regime class: perudic
Seasonal pattern: Precipitation falls mostly even during the year with the exception of February to April being the driest months averaging 179 to 229 millimeters (7 to 9 inches) per month.
Mean annual soil temperature: 27 C (81 F)
Control section: 25 to 100 centimeters (10 to 39 inches)
Thickness of solum: 50 to 100 centimeters (20 to 39 inches.)
Depth to diagnostic feature: aquic conditions: 100 to 150 centimeters (39 to 59 inches)
episaturation: 100 to 150 centimeters (39 to 59 inches)
Thickness of diagnostic feature: ochric epipedon: 25 to 40 centimeters (10 to 16 inches)
fibric soil materials: 5 to 15 centimeters (2 to 6 inches)
Linear extensibility: 0 to 1 percent, weighted average RV is 0.5 percent
Surface Fragments: Rock fragments are hard angular coralline limestone; 60 to 90 percent total rock fragments; 30 to 50 percent gravel; 30 to 40 percent cobbles
Seasonal high water table: All months of the year
Depth to top: 100 to 150 centimeters (39 to 59 inches)

Oi horizon(s):
Hue: 7.5YR or 10YR
Value: 2 through 3
Chroma: 1 to 2
In lieu of texture: slightly decomposed plant material and is extremely or very cobbly
Fragment size and content: Rock fragments are hard subrounded coralline limestone; 35 to 90 percent total rock fragments; 25 to 40 percent gravel; 15 to 35 coarse cobbles; 0 to 15 percent stones
Calcium carbonate equivalent: 0 to 5 percent
Electrical conductivity: 0 to 5 mmhos/cm
Reaction: neutral to slightly alkaline
Cation Exchange Capacity 135 to 180 meq/100grams
Organic matter content: 60.0 to 100.0 percent

A horizon(s):
Hue: 7.5YR or 10YR
Value: 2 through 3
Chroma: 1 to 2
Texture: sand and loamy sand and is extremely or very cobbly
Fragment size and content: Rock fragments are hard subrounded coralline limestone; 35 to 90 percent total rock fragments; 25 to 40 percent gravel; 15 to 35 coarse cobbles; 0 to 15 percent stones
Clay content: 5 to 15 percent
Carbonate clay content: 5 to 9 percent
Silt content: 5 to 20 percent
Sand content: 60 to 85 percent
Calcium carbonate equivalent: 70 to 95 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 7.0 to 7.8
Cation Exchange Capacity: 10 to 30 meq/100grams
Organic matter content: 4 to 13 percent

AC horizon(s):
Hue: 7.5YR or 10YR.
Value: 4 through 8
Chroma: 2 to 5
Texture: sand and loamy sand and is highly organic and is extremely or very cobbly
Fragment size and content: Rock fragments are hard subrounded coralline limestone; 35 to 90 percent total rock fragments; 25 to 40 percent gravel; 15 to 35 coarse cobbles; 0 to 15 percent stones
Silt content: 0 to 5 percent
Clay content: 0 to 5 percent
Carbonate clay content: 0 to 5 percent
Sand content: 80 to 100 percent
Calcium carbonate equivalent: 90 to 98 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 7.8 to 8.3
Cation Exchange Capacity: 0.0 to 2.5 meq/100grams
Organic matter content: 0 to 0.5 percent

C horizon(s):
Hue: 7.5YR or 10YR.
Value: 4 to 8 moist.
Chroma: 2 to 4 moist
Texture: sand and loamy sand and is highly organic and is extremely or very cobbly
Fragment size and content: Rock fragments are hard subrounded coralline limestone; 35 to 90 percent total rock fragments; 25 to 40 percent gravel; 15 to 35 coarse cobbles; 0 to 15 percent stones
Silt content: 0 to 6 percent
Clay content: 2 to 6 percent
Carbonate clay content: 1 to 6 percent
Sand content: 90 to 98 percent
Calcium carbonate equivalent: 90 to 98 percent
Reaction: slightly alkaline to moderately alkaline
Cation Exchange Capacity: 0 to 1.8 meq/100grams
Organic matter content: 0 to 0.1 percent

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

GEOGRAPHIC SETTING: Majuro soils are on beach ridges, beach terraces, and beaches, of atolls, karsts, and islands, generally on oceansides of islands. They are dominant under Atoll and Casuarina Forest plant communities. Slope is 0 to 6 percent. Theses soils formed in water- and wind-deposited coralline sand and rubble. Elevation is 0 to 6 meters (0 to 20 feet.) 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.) The seasonal wet (May to November) and dry seasons (December to April) with the driest months (February, March, and April) averaging 178 to 229 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. These soils lie within the latitudinal zone that receives more solar radiation than it re-radiates back to space. This imbalance maintains the atmospheric temperatures in a quasi-steady state. 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 Dublon, Ngedebus, Ngerungor, and Odesangel soils. Dublon soils have a water table at 38 to 91 centimeters (15 to 36 inches) depth. Ngedebus soils are near Majuro soils but are generally on the lagoon side of islands and have less than 35 percent coral fragments in the particle-size control section. Odesangel soils formed in depressional areas that retain fresh or brackish water. The soils are derived dominantly from decomposed and partially decomposed freshwater marsh vegetation overlying coral sand. Ngerungor soils have hemic materials greater than 125 centimeters (49 inches), occur in depressional areas and are saturated throughout the profile.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat excessively drained. Low runoff, high saturated hydraulic conductivity.

USE AND VEGETATION: These soils are in casuarina atoll-forest plant communities and are used for native forests, fuelwood, and agroforestry. A few areas are used for homesites or recreation use. Agroforestry crops is comprised of, Manihot esculenta (cassava), sweet potato, and tomato. Of the total fruit tree, there are banana trees, breadfruit, betel nut, citrus (lemon and lime), coconut trees, guava, mountain apple, and papaya trees. Native species commonly observed in the overstory of atoll forests include; Casuarina equisetifolia, Calophyllum inophyllum, Hernandia sonora, Guettarda speciosa, Pisonia grandis, Neisosperma oppositifolia, and Ficus spp. Understory forest species include Scaevola taccada, Tournefortia argentea, Pemphis acidula, Pandanus spp., Morinda citrifolia, and Premna obtusifolia. There was little groundcover in the atoll forest plant community. A few areas are in Casuarina forest and are used for recreation.

Atoll forests provide habitat for coastal wildlife species. The potential to develop and use atoll forest is limited. Atoll forests are generally unsuited for agriculture and agroforestry because of the sandy soils and their close proximity to the ocean and salt spray. Small areas within the atoll forests could be suitable for agroforestry if sufficient organic matter for composting is available. The atoll forests are generally suitable for coconut (Cocos nucifera) plantings. Untended plantings or natural regeneration of coconuts was observed. The low economic return in coconut plantings would discourage this use of atoll forests.

DISTRIBUTION AND EXTENT: MRLA 193 Volcanic Islands of Western Micronesia; Republic of Palau; Yap State, Federated States of Micronesia; MRLA 195 Volcanic Islands of Central and Eastern Micronesia; Kosrae State; Federated States of Micronesia; MLRA 196 Coral Atolls of Micronesia; Republic of the Marshal Islands; MRLA 197 Volcanic Islands of American Samoa; Territory of American Samoa, and Federated States of Micronesia. The soils of this series are of small extent; about 500 acres in Palau, about 250 acres total in the Federated States of Micronesia, Kosrae (80), Yap (175), about 175 acres in American Samoa; and about 1100 acres in the Marshal Islands. They are mapped on the islands of Angaur, Fana, Helen Reef, Kayangel Atoll, Merir, Ngerechong, Pulo Ana, Peleliu, Sonsorol, and Ulong in the Palau islands; Yap Islands; Ulithi atoll; Fais; the coastal strand of Kosrae; Airik, Arno, Majuro, Mili and Taroa islands in the Marshall Islands and Aunu`u, Tutuila and Manua Islands in American Samoa.

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

SERIES ESTABLISHED: Mili Island, Mili Atoll in the Republic of the Marshall Islands; 1987. Actually this series did not get established until 2008 by a strange twist of soil survey fate.

REMARKS: The Majuro soil series was composed of soils published as the Ngedebus Variant in the soil surveys of American Samoa, Kosrae, Palau, and Yap. These soils have a high percentage of coarse fragments and sand. This results in low soil water holding capacity. They are especially susceptible to droughty conditions. The coralline sand parent material is 97 percent calcium carbonate, which is lacking in most essential nutrients. In addition, there is rapid decomposition of soil organic matter. Maintenance of soil fertility requires continual input of plant biomass. Burning the forest as a method of clearing land for agriculture removes the nutrients that have accumulated in the soil humus. Soil chemical properties are not affected by a strong rainfall gradient across the pacific, but human activity has a greater effect on some properties. Managing organic matter is fundamental to the cropping systems on these soils.

Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - Surface to 32 cm (13 inches)
Aquic conditions - 148 cm (58 inches)
Episaturation -148 cm (58 inches)
Particle-size control section - 25 to 100 cm (10 to 39 inches)

ADDITIONAL DATA: National Soil Survey Laboratory Data # 06PW150001 (Ngedebus.) Additional data are: Nutrient Content of Majuro Soils, Island of Angaur - Sample number: S2, S12; pH: 7.7, 7.3; Organic Matter (%): 2, 6; Nitrogen (%):0.17, 0.89; Phosphorus (ppm): 5, 12; Potassium (ppm):16, 20; Calcium (ppm): 4170, 4156; Magnesium (ppm):184, 180

Taxonomic Version: Keys to Soil Taxonomy, 10th edition 2006.

National Cooperative Soil Survey
U.S.A.