LOCATION POLACCA AZEstablished Series
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, mesic Typic Haplocambids
TYPICAL PEDON: Polacca clay loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 3 inches; pale brown (10YR 6/3) clay loam, yellowish brown (10YR 5/4) moist; moderate medium platy structure; soft, very friable, moderately sticky and moderately plastic; common very fine roots; many very fine vesicular pores; strongly effervescent; moderately alkaline; abrupt smooth boundary. (2 to 4 inches thick)
A2--3 to 9 inches; yellowish brown (10YR 5/4) clay, dark yellowish brown (10YR 4/4) moist; weak medium platy structure; hard, firm, very sticky and very plastic; common very fine roots; few very fine, tubular pores; few very fine lime coatings along plates; strongly effervescent; moderately alkaline; abrupt smooth boundary. (2 to 7 inches thick)
A3--9 to 14 inches; light yellowish brown (10YR 6/4) stratified very fine sandy loam and silt loam, yellowish brown (10YR 5/4) moist; moderate medium platy structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; many very fine tubular pores; strongly effervescent; moderately alkaline; abrupt smooth boundary. (3 to 7 inches thick)
Bw--14 to 26 inches; yellowish brown (10YR 5/4) clay, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; very hard, firm, very sticky and very plastic; many very fine roots; many very fine tubular pores; a few cutans of organic matter and silt on faces of peds; strongly effervescent; moderately alkaline; abrupt smooth boundary. (7 to 13 inches thick)
2Bk--26 to 33 inches; brown (7.5YR 5/4) sandy clay loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; common very fine tubular pores; few fine irregular lime masses and common accumulations in root channels; organic coats on faces of peds; strongly effervescent; moderately alkaline; abrupt smooth boundary. (6 to 8 inches thick)
3C--33 to 84 inches; light yellowish brown (10YR 6/4) loamy sand with a few thin strata of very fine sandy loam, yellowish brown (10YR 5/4) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; slightly effervescent; moderately alkaline.
TYPE LOCATION: Navajo County, Arizona about 15 miles southwest of Second Mesa, about 1.5 miles west of Elbow Point; about 2800 feet west and 500 feet north of the southeast corner of Sec. 8, T. 25 N., R. 16 E.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in some part of the soil moisture control section during December-February and July-September. The soil is driest during May and June. Typic aridic soil moisture regime.
Soil temperature - 53 to 56 degrees F.
Coarse fragments - 0 to 2 percent gravel in series control section, lacking in most pedons
Depth to contrasting particle-size - Typically 26 to 36 inches but ranges from 20 to 39 inches
A horizon
Value: 4 to 6 dry, 4 or 5 moist
Chroma: 3 or 4, dry or moist
Texture: (15 to 30 percent clay) Stratified very fine sandy loam to clay. This horizon is stratified in most pedons.
Carbonates: less than 15 percent calcium carbonate equivalent
Reaction: slightly alkaline to moderately alkaline
B horizon
Hue: 7.5YR, 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4, dry or moist
Texture: sandy clay loam, clay loam, clay; can have thin strata of coarser material
Carbonates: less than 15 percent calcium carbonate equivalent; secondary lime as fillings and masses in the lower part
Reaction: slightly alkaline or moderately alkaline
C horizon
Texture: loamy sand, sand (3 to 8 percent clay); has 2 to 10 thin strata (1 to 5 cm thick) of very fine sandy loam
Carbonates: less than 15 percent calcium carbonate equivalent
COMPETING SERIES: This is the Oreanna (OR) series. Oreanna soils have 40 to 60 percent rock fragments in the lower part of the particle-size control section and has mean annual soil temperature that ranges from 47 to 50 degrees F.
GEOGRAPHIC SETTING: Polacca soils are on stream terraces with slope gradients of 0 to 3 percent. Flooding is rare and very brief. Elevations are 5100 to 6000 feet. They formed in stream alluvium derived from sedimentary rocks, dominantly shale and sandstone. The climate is cool, arid and continental with precipitation of 6 to 10 inches which occurs as thunderstorms in July, August, and September and as rain and snow in December, January, and February. The average annual air temperature ranges from 51 to 54 degrees F. Frost-free period ranges from 130 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Jocity, Tewa, and Wepo soils. Jocity soils are on alluvial fans and flood plains and are stratified throughout. Tewa and Wepo soils are on stream terraces. Tewa soils are fine-loamy and Wepo soils are fine. Both lack contrasting particle size.
DRAINAGE AND PERMEABILITY: Well drained. Slow runoff. Slow permeability in the upper part, rapid in the lower part.
USE AND VEGETATION: Used primarily for grazing. Vegetation includes alkali sacaton, galleta, bottlebrush squirreltail, fourwing saltbush, and winterfat.
DISTRIBUTION AND EXTENT: Northeast Arizona. MLRA 35, LRR-D. The soils of this series are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Navajo County, Arizona, 1985. Hopi Area, Parts of Coconino and Navajo Counties.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Cambic horizon - The zone from 14 to 26 inches (Bw horizon)
Secondary carbonates - The zone from 26 to 33 inches (2Bk horizon)
Contrasting textures - An abrupt textural change at 33 inches
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006
Updated and revised for the correlation of Ft. Defiance Area AZ715 2/08 DWD