LOCATION NIWOT CO
Established Series
Rev. GB-KLS
05/2023
NIWOT SERIES
The Niwot series consists of deep, somewhat poorly to poorly drained soils formed in mixed alluvial parent materials overlying beds of sand and gravel. Niwot soils are on flood plains or low terraces and have slopes of 0 to 6 percent. Mean annual precipitation is about 380 cm and mean annual temperature is about 9 degrees C.
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, mesic Typic Endoaquolls
TYPICAL PEDON: Niwot loam - grassland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 15 cm; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; moderate fine granular structure; soft, very friable; slightly alkaline (pH 7.4); clear smooth boundary. (10 to 20 cm thick)
A2--15 to 36 cm; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak coarse subangular blocky structure parting to moderate fine granular; soft, very friable; common medium distinct strong brown (7.5YR 5/6) redoximorphic concentrations; slightly alkaline (pH 7.4); gradual wavy boundary. (15 to 41 cm thick)
2Cg--36 to 152 cm; pale brown (10YR 6/3) gravelly sand, brown (10YR 5/3) moist; single grain; loose; many large prominent strong brown (7.5YR 5/6) redoximorphic concentrations; neutral (pH 7.2).
TYPE LOCATION: Boulder County, Colorado; 674 meters south and 30 meters west of the of the center of Sec. 10, T. 1 N., R. 69 W.; Erie USGS quad; lat. 40 degrees, 3 minutes, 33 seconds N., 105 degrees, 6 minutes, 11 seconds W., NAD83
RANGE IN CHARACTERISTICS:
Soil moisture - these soils have fluctuating high water tables and are saturated in some months of most years
Mean annual soil temperature - 8 to 14 degrees C
Mean summer soil temperature - 15 to 26 degrees C
Mollic epipedon thickness - 18 to 50 cm
Depth to contrasting sand or sand and gravel substratum - 30 to 50 cm
Organic carbon content in the mollic epipedon - 0.8 to 3 percent, decreasing uniformly with depth
Salt content more soluble than gypsum - normally less than 2 percent and does not exceed 4 percent above 100 cm
Base saturation - 90 to 100 percent
Particle-size control section:
Texture - loam or clay loam over sand or gravelly sand
Clay content - 18 to 35 percent
Sand content - 20 to 50 percent, with more than 15 percent but less than 35 percent fine sand or coarser
A horizon
Hue: 5Y through 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 1 or 2 dry or moist
Texture: loam or clay loam
Rock fragment content: 0 to 15 percent rounded gravel and cobbles
Reaction: pH 6.1 to 7.4
2Cg horizon
Hue: 5Y through 10YR and contains many large prominent mottles
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4 dry or moist
Reaction: pH 6.1 to 7.4, little change in pH with depth
Texture: loamy sand or sand
Rock fragment content: 10 to 50 percent rounded gravel and cobbles
Note: some pedons have a clayey substratum below depths of 100 cm
COMPETING SERIES:
Biscay (MN) - depth to contrasting textures is more than 50 cm
Marshan (MN) - depth to contrasting textures is more than 50 cm
Mudhen (IL) - depth to contrasting textures is more than 50 cm; are deep to paralithic contact
Will (IL) - depth to contrasting textures is more than 50 cm
GEOGRAPHIC SETTING:
Landform - flood plains or low terraces
Elevation - 1,500 to 2,150 meters
Slope - 0 to 6 percent
Parent material - mixed alluvial parent material overlying beds of sand and gravel
Mean annual air temperature - 7 to 10 degrees C
Mean annual precipitation - 305 to 460 mm
Precipitation pattern - peaks periods of precipitation occur in the spring and summer months
Frost-free period - 100 to 150 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Somewhat poorly to poorly drained; runoff is slow; permeability is medium to rapid above the water table.
USE AND VEGETATION: Used as native pastureland or irrigated hay meadow. Principal native vegetation is bromegrass, orchard grass, wheatgrass, junegrass, and water-tolerant grasses and sedges.
DISTRIBUTION AND EXTENT: Niwot soils are of small extent in the foothills along the eastern front of the Rocky Mountains in central Colorado; MLRA 49.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Boulder Area, Colorado, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic horizon - 0 to 36 cm (A1 and A2 horizons)
Contrasting texture change - 36 to 152 cm (2Cg horizon)
Particle-size control section - 25 to 100 cm (part of A2 and 2Cg horizons)
Niwot soils have a mesic soil temperature regime and an ustic soil moisture regime bordering on aridic.
Converted to metric, formatting updated to current standards, and competing series section updated. 05/2020
National Cooperative Soil Survey
U.S.A.