LOCATION SCHROCK                 AK

Established Series
Rev. DBS-SR-JPM
02/2022

SCHROCK SERIES

Schrock series consists of very deep, well to moderately well drained soils formed in a thick mantle of ash-influenced loess and alluvium overlying coarser textured alluvium. Schrock soils are on alluvial terraces and floodplains. Slopes range from 0 to 7 percent. The mean annual temperature is about 34 degrees F., and the average annual precipitation is about 25 inches.

TAXONOMIC CLASS: Medial over loamy, mixed, superactive Entic Haplocryods

TYPICAL PEDON: Schrock silt loam - on a 2 percent slope under spruce and birch forest at 375 feet elevation (All colors are for moist soil)

Oi--3 inches to 0; dark reddish brown (5YR 2/2) mat of slightly decomposed moss, leaves, and twigs; many fine roots; mycelia; extremely acid; clear wavy boundary. (1 to 4 inches thick)

A--0 to 3 inches; dark brown (7.5YR 3/2) silt loam; moderate fine granular structure; very friable; many roots; very strongly acid; clear wavy boundary. (1 to 6 inches thick)

Bs--3 to 8 inches; dark brown (7.5YR 4/3) silt loam; weak fine granular structure; friable, nonsticky and nonplastic; streaks of dark yellowish brown (10YR 4/4); common roots; very strongly acid; gradual wavy boundary. (4 to 10 inches thick)

BC--8 to 18 inches; olive brown (2.5Y 4/4) silt loam; weak thin platy structure; friable, nonsticky and nonplastic; few large patches of light olive brown (2.5Y 5/4) and dark yellowish brown (10YR 4/4); common roots; few horizontal very dark brown streaks of buried organic material; few strata of fine sand (1/4 to 1/2 inch thick); strongly acid; gradual wavy boundary. (6 to 14 inches thick)

2C--18 to 42 inches; dark grayish brown (2.5Y 4/2) stratified silt loam and fine sand; massive; very friable, nonsticky and nonplastic; few roots to 24 inches; few strata of gray medium and coarse sand; few rounded pebbles in lower part of horizon; strongly acid. (15 to 30 inches thick)

3C--42 to 60 inches; variegated very cobbly fine sandy loam.

TYPE LOCATION: Susitna Valley Area, Alaska; northeast of Talkeetna Airport and 50 feet south of road; 0.5 mile east of the northwest corner of section 20, T.26N, R.4W., Seward Meridian.

RANGE IN CHARACTERISTICS: Thickness of the loess mantle and the solum ranges from 14 to 30 inches. The exchange complex of the solum is dominated by amorphous material. The upper 4 inches of the spodic horizons have less than 1.2 percent organic carbon. Coarse fragment content within the control section below the solum is less than 35 percent. Reaction throughout the profile ranges from very strongly acid to moderately acid.

Where present, the texture of the A horizon is silt loam or very fine sandy loam.

Thin E horizons are present in many pedons. Value moist is 4 or 5, and chroma moist is 1 or 2. Texture is silt loam or very fine sandy loam.

The Bs horizon has, value moist of 3 or 4; and chroma moist from 2 through 4.

The BC horizon has hue of 10YR or 2.5Y; value moist from 4 to 6 and chroma moist from 2 to 6.

The 2C horizon is variegated, but with a dominant hue from 10YR to 2.5Y.

COMPETING SERIES: This is the Scar series in the same family. Scar soils have textures of sandy loam or coarser in the control section.

GEOGRAPHIC SETTING: Schrock soils are on low alluvial terraces and floodplains. Slope ranges from 0 to 7 percent. Schrock soils formed in stratified ash-influenced eolian and alluvial deposits overlying coarse textured alluvium below 40 inches. The mean annual temperature ranges from 32 to 36 degrees F. The average annual precipitation ranges from 17 to 32 inches.

DRAINAGE AND PERMEABILITY: Well to moderately well drained. Slow runoff. Moderate permeability in the upper part and rapid in the gravelly underlying material.

USE AND VEGETATION: Mostly forested. The dominant trees are paper birch, white spruce, and cottonwood. Small areas are cleared and used mainly for bromegrass, small grain, and hardy vegetables.

DISTRIBUTION AND EXTENT: South-central Alaska. The series is of moderate extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA

SERIES ESTABLISHED: Matanuska Valley Area, Alaska, 1966.

REMARKS: Diagnostic horizons and features recognized in this pedon include: spodic horizon from 3 to 18 inches; cryic temperature regime; assumed organic carbon content less than 1.2 percent from 3 to 7 inches; an exchange complex dominated by amorphous material from 0 to 18 inches; loamy particle size from 18 to 42 inches.

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National Cooperative Soil Survey
U.S.A.