LOCATION NEKOMA                  OR

Established Series
Rev. WRP/MHF/RWL
06/2011

NEKOMA SERIES

The Nekoma series consists of very deep, well or moderately well drained soils that formed in recent loamy alluvium over stratified loamy to sandy alluvium derived from sandstone and siltstone. Nekoma soils occur on flood plains. Slopes are 0 to 3 percent. The mean annual precipitation is about 80 inches and the mean annual temperature is about 51 degrees F.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Fluventic Humudepts

TYPICAL PEDON: Nekoma silt loam, woodland. (Colors are for moist soil unless otherwise noted.)

Oi--0 to 1 inch; slightly decomposed duff layer of moss, needles and twigs.

A1--1 to 6 inches; very dark brown (10YR 2/2) silt loam, dark grayish brown (10YR 4/2) dry; weak medium subangular blocky structure parting to moderate very fine granular; slightly hard, very friable, nonsticky and slightly plastic; few medium and fine, and common very fine roots; many very fine irregular pores; moderately acid (pH 5.8); clear smooth boundary.

A2--6 to 12 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) and brown (10YR 5/3) dry; moderate medium and fine subangular blocky and granular structure; soft, very friable, nonsticky and nonplastic; common medium, fine, and very fine roots; many very fine irregular pores; moderately acid (pH 6.0); clear wavy boundary. (combined A horizon is 10 to 20 inches thick)

Bw--12 to 21 inches; brown (10YR 4/3) fine sandy loam, very pale brown (10YR 7/4) dry; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; few medium, fine and very fine roots; many very fine irregular pores; moderately acid (pH 5.8); gradual wavy boundary. (8 to 20 inches thick)

C1--21 to 34 inches; brownish yellow (10YR 6/6) loamy fine sand, very pale brown (10YR 7/4) dry; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; many very fine irregular pores; moderately acid (pH 5.6); abrupt smooth boundary. (0 to 15 inches thick)

C2--34 to 42 inches; yellowish brown (10YR 5/6) fine sandy loam, very pale brown (10YR 7/3) dry; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; many very fine irregular pores; strongly acid (pH 5.4); abrupt smooth boundary. (8 to 20 inches thick)

C3--42 to 61 inches; brownish yellow (10YR 6/6) loamy fine sand, very pale brown (10YR 7/4) dry; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; many very fine irregular pores; very strongly acid (pH 5.0).

TYPE LOCATION: Lane County, Oregon; about 200 feet south of the Siuslaw River Road; about 600 feet north and 200 feet west of the SE corner of section 20, T. 19 S., R. 7 W.; Clay Creek, OR 7.5 minute USGS Quad, NAD 1927.

RANGE IN CHARACTERISTICS: The mean annual soil temperature is 49 to 55 degrees F. The soil is usually moist, but is dry in all parts between depths of 4 and 12 inches for a period of less than 45 consecutive days in the four month period following the summer solstice in most years. The umbric epipedon is 10 to 20 inches thick. The particle size control section averages 5 to 15 percent clay, and has more than 15 percent of the sand fraction which is fine sand or coarser. Below depths of 40 inches iron depletions with chroma of 2 or less and masses of oxidized iron with chroma of more than 2 may occur. Hue is 10YR or 7.5YR.

The A horizon has value of 2 or 3 moist, 3 to 5 dry and chroma of 2 or 3 moist and dry. Texture is silt loam or loam with 5 to 20 percent clay and 0 to 10 percent gravel. Soil reaction is strongly or moderately acid.

The Bw horizon has value of 3 to 5 moist, 5 to 7 dry and chroma 3 to 6 moist and dry. Texture of the fine-earth fraction is dominantly is fine sandy loam, loam or silt loam with 5 to 15 percent clay and 0 to 20 percent gravel. The lower part may be stratified with thin lenses of loamy fine sand and loam. Soil reaction is very strongly acid to moderately acid.

The C horizon has value of 3 to 6 moist, 5 to 7 dry and chroma of 3 to 6 moist and dry. This horizon typically is stratified loamy fine sand to very fine sandy loam with 5 to 15 percent clay and 0 to 30 percent gravel. Some pedons may have lenses of gravelly or very gravelly loamy sand below a depth of 40 inches with up to 50 percent gravel. Soil reaction is very strongly acid to moderately acid.

COMPETING SERIES: These are the Edgewick and Rosman series. Edgewick soils have a mean annual soil temperature of 47 to 49 degrees F., have an umbric epipedon 7 to 12 inches thick, become less acid with depth and are neutral or slightly acid in the lower part of the particle-size control section., . Rosman soils have a mean annual soil temperature of 55 to 59 degrees F., lack a short dry period in the summer, are moderately well drained, and have few to many mica flakes throughout.

GEOGRAPHIC SETTING: The Nekoma soils occur on flood plains. Elevations are 10 to 750 feet. Slopes are 0 to 3 percent. Nekoma soils formed in recent loamy alluvium over stratified loamy to sandy alluvium derived from sandstone and siltstone. The climate is characterized by warm, wet winters and hot, moist summers. The mean annual precipitation is 60 to 100 inches. The mean July temperature is about 62 degrees F. and the mean January temperature is about 40 degrees F. The mean annual temperature is 48 to 54 F. The frost-free period is 140 to 240 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gardiner, Kirkendall, Meda, Quosatana, and Wasson soils. All of these soils occur on flood plains except the Meda series, which occurs on alluvial fans. Quosatana and Wasson soils are poorly drained. Gardiner soils are sandy throughout the particle-size control section. Kirkendall soils are fine-silty. Meda soils are fine-loamy. Both Kirkendall and Meda have more than 18 percent clay in the particle-size control section.

DRAINAGE AND PERMEABILITY: Well or moderately well drained; moderately rapid permeability. These soils are subject to frequent periods of flooding for brief durations from November through April. A seasonal water table is at its uppermost limit from November through April.

USE AND VEGETATION: These soils are used for pasture, forage crops, home gardens and woodland. Native vegetation is Douglas-fir, western hemlock, red alder, salal, vine maple, salmonberry, red huckleberry, western swordfern and other shrubs, forbs and grasses.

DISTRIBUTION AND EXTENT: Flood plains of Coast Range river valleys in western Oregon; MLRA 1. The soils are of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Lane County Area, Oregon, 1981.

REMARKS: Diagnostic horizons and features of this pedon include:

Umbric epipedon - from 1 to 12 inches (A1 and A2 horizons).
Cambic horizon - from 12 to 21 inches (Bw horizon).
Fluventic feature - the soil is assumed to have an irregular decrease in organic carbon content

Depth to diagnostic horizons and features are measured from the top of the first mineral layer.

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National Cooperative Soil Survey
U.S.A.