LOCATION POTATO                  AZ

Established Series
Rev. JMH/CRF/MJA
02/2025

POTATO SERIES

The Potato series consists of moderately deep, well drained soils that formed in colluvium over residuum derived from rhyolite. Potato soils are on sideslopes of lava domes. Slopes range from 2 to 36 percent. Mean annual precipitation is about 24 inches and the mean annual temperature is about 43 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Udic Haplustalfs

TYPICAL PEDON: Sponseller-Potato complex (Colors are for dry soil unless otherwise noted.)

A--0 to 2 inches (0 to 6 cm); light brownish gray (10YR 6/2), very gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; weak medium granular; loose, loose, slightly sticky, slightly plastic; few very fine dendritic tubular pores; few very fine and fine roots throughout; 5 percent cobbles and 55 percent gravel; noneffervescent; slightly alkaline (pH 7.8); clear smooth boundary

Bt1--2 to 10 inches (6 to 25 cm); brown (7.5YR 4/4) very gravelly sandy clay loam, dark brown (7.5YR 3/4) moist; moderate fine angular blocky; soft, very friable, slightly sticky, slightly plastic; few very fine dendritic tubular pores; common very fine and fine, and few coarse roots throughout; 15 percent faint clay films on vertical faces of peds; 40 percent gravel; noneffervescent; slightly alkaline (pH 7.4); clear irregular boundary

Bt2--10 to 16 inches (25 to 40 cm); brown (10YR 5/3) gravelly loam, dark yellowish brown (10YR 4/4) moist; moderate medium angular blocky; hard, firm, moderately sticky, moderately plastic; few very fine dendritic tubular pores; few very fine, fine, and very coarse roots throughout; 15 percent faint clay films on vertical faces of peds; 30 percent gravel; noneffervescent; slightly alkaline (pH 7.6); clear wavy boundary

C--16 to 21 inches (40 to 54 cm); pale brown (10YR 6/3) extremely gravelly sandy clay loam, brown (10YR 4/3) moist; structureless massive; loose, loose, very sticky, very plastic; common interstitial pores; few very fine and fine roots throughout; 10 percent stones, 10 percent cobbles, and 55 percent gravel; noneffervescent; slightly alkaline (pH 7.4); clear irregular boundary

R--21 to 31 inches (54 to 79 cm); rhyolite bedrock

TYPE LOCATION: Coconino County, Arizona; located about 5.4 kilometers (3.4 miles) southwest of Pumpkin Center, Arizona; USGS Quadrangle Moritz Ridge; Latitude 35.46664, Longitude -111.94041, Datum WGS84.

RANGE IN CHARACTERISTICS:
Soil moisture regime: ustic bordering on udic
Mean annual soil temperature: 42 to 46 degrees F
Rock fragment content: 35 to 60 percent
Depth to lithic contact: over 50 centimeters
Particle-size control section:
Clay content: 18 to 27 percent

A horizon
Hue: 7.5YR or 10YR
Value: 4 to 6 (3 or 4 moist)
Chroma: 2 or 3, dry or moist
Calcium carbonate equivalent: 0 to 2 percent
Reaction: neutral or slightly alkaline

Bt horizons
Hue: 7.5YR or 10YR
Value: 4 or 5 (3 or 4 moist)
Chroma: 3 or 4, dry or moist
Texture: sandy clay loam or loam
Calcium carbonate equivalent: 0 to 2 percent
Sodium Adsorption Ratio (SAR): 0 to 2
Reaction: neutral or slightly alkaline

C horizon
Hue: 7.5YR or 10YR
Value: 5 or 6 (3 or 4 moist)
Chroma: 3 or 4, dry or moist
Texture: sandy clay loam or loam
Calcium carbonate equivalent: 0 to 2 percent
Sodium Adsorption Ratio (SAR): 0 to 2
Reaction: neutral or slightly alkaline

COMPETING SERIES: This is the Abreu (NM) series.
Abreu soils are more frequently moist in spring, and are controlled by Bozeman, MT.

GEOGRAPHIC SETTING:
Parent material: colluvium over residuum derived from rhyolite
Landform: lava domes
Slopes: 2 to 36 percent
Elevation: 7,200 to 9,000 feet
Mean annual air temperature: 41 to 45 degrees F
Mean annual precipitation: 22 to 26 inches
Precipitation peaks in July and August, and in winter. May and June are much drier.
Frost-free period: 80 to 100 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Sponseller soils. Sponseller soils are on slope alluvium over residuum.

DRAINAGE AND PERMEABILITY: well drained, moderate permeability

USE AND VEGETATION: These soils are used principally as grazing land. Native vegetation is mainly alligator juniper, douglas fir, wax currant, white fir, blue grama, and muttongrass.

DISTRIBUTION AND EXTENT: Northern Arizona. MLRA 39.

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

SERIES ESTABLISHED: Coconino County, Arizona.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: from 0 to 6 centimeters. (A horizon)
Argillic horizon: from 6 to 40 inches. (Bt horizons).
Name is taken from nearby Potato Hill
Taxonomic Version: Keys to Soil Taxonomy, Thirteenth Edition, 2022
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National Cooperative Soil Survey
U.S.A.