LOCATION TOPAWA AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Typic Haplargids
TYPICAL PEDON: Topawa very gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; brown (7.5YR 5/4) very gravelly sandy loam, brown (7.5YR 4/4) moist; weak medium platy structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; common fine interstitial pores; 40 percent gravel; noneffervescent; neutral (pH 7.0); abrupt smooth boundary. (1 to 4 inches thick)
Bt1--2 to 8 inches; reddish brown (5YR 4/4) extremely gravelly sandy loam, dark red (2.5YR 3/6) moist; moderate fine subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common fine and very fine roots; common fine interstitial and tubular pores; many distinct continuous clay films on rock fragments and clay bridging sand grains; 70 percent gravel; noneffervescent; neutral (pH 7.2); abrupt smooth boundary. (4 to 10 inches thick)
Bt2--8 to 18 inches; reddish brown (5YR 4/4) very gravelly sandy clay loam, dark red (2.5YR 3/6) moist; moderate fine subangular blocky structure; very hard, firm, sticky and plastic; common fine and very fine roots; few fine tubular pores; many distinct continuous clay films on rock fragments, on faces of peds, in pores, and bridging sand grains; 40 percent gravel; noneffervescent; neutral (pH 7.2); clear wavy boundary. (10 to 20 inches thick)
Bt3--18 to 37 inches; yellowish red (5YR 4/6) extremely cobbly sandy clay loam, dark reddish brown (2.5YR 3/4) moist; moderate fine subangular blocky structure; very hard, firm, sticky and plastic; few fine roots; few fine tubular pores; many distinct continuous clay films on rock fragments, on faces of peds, and in pores; 30 percent cobble and 45 percent gravel; noneffervescent; neutral (pH 7.2); clear wavy boundary. (10 to 20 inches thick)
Bt4--37 to 60 inches; yellowish red (5YR 5/6) gravelly sandy loam, yellowish red (5YR 4/6) moist; massive; hard, firm, slightly sticky and slightly plastic; few fine roots; many fine interstitial pores; few distinct continuous clay films on faces of peds, bridging sand grains and on gravel; 25 percent gravel; noneffervescent; slightly alkaline (pH 7.6). (10 to 20 inches thick)
TYPE LOCATION: Pima County, Arizona; latitude of 32 degrees, 5 minutes, 5 seconds north and a longitude of 111 degrees, 49 minutes, 0 seconds, west. Comobabi topographic map, northwest of the village of Comobabi. 2,180 feet east and 320 feet north of the SW corner of Sec. 25, T. 15 S., R. 5 E.
RANGE IN CHARACTERISTICS:
Soil moisture: Intermittently moist in some part of the soil moisture control section during July - September and December - February. Driest during May and June. Typic Aridic soil moisture regime.
Soil temperature: 69 to 72 degrees F.
Rock fragments: greater than 35 percent gravel and cobble in the control section
Clay content: averages more than 18 percent in the control section
Organic matter: less than 1 percent
A horizon
Hue: 7.5YR, 5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 4 through 6 dry, 3 or 4 moist
Reaction: neutral to slightly alkaline
Calcium carbonate: noneffervescent
Bt horizons
Hue: 2.5YR, 5YR
Value: 3 through 5 dry, 3 or 4 moist
Chroma: 3 through 6, dry or moist
Texture: sandy loam, sandy clay loam, clay loam
Reaction: neutral to moderately alkaline
Calcium carbonate: noneffervescent to strongly effervescent; less than 10 percent calcium carbonate equivalent
COMPETING SERIES: These are the Ashmed (NV), Bitter (CA), Blind (AZ), Bluebird (AZ), Highland (NV), Khyber (CA), Nellake (CA), Soledad (NM), Tiefort (I)(CA), Timosea (CA), Twobitter (CA) and Werewolf (CA) series. Ashmed, Bitter, Highland, Khyber, Nellake and Timosea soils are moist in the soil moisture control section for less than 20 days between July and September. Blind soils have hue of 10YR or 7.5YR and mean annual soil temperatures of 61 to 66 degrees F. Ashmed soils have a SAR of 13 to 35 in the argillic horizon and hue of 10YR. Bitter soils are less than 30 inches deep to the base of the argillic and have loamy sand and sand textures below the argillic. Bluebird soils are less than 23 inches to the base of the argillic. Highland soils have a lithic contact within 40 inches. Khyber soils are dominated by 2 to 5 millimeter gravel and have secondary silica cementation in the lower part of the subsoil. Nellake soils average less than 20 percent clay in the argillic horizon and less than 15 percent clay in the subsoil. Twobitter soils have accumulations of gypsum in the particle-size control section. Soledad soils average less than 20 percent clay in the control section. Timosea soils have hue of 7.5YR or 10YR. Tiefort soils are inactive.
GEOGRAPHIC SETTING: Topawa soils are on fan terraces. Slopes range from 0 to 10 percent, but are dominantly 1 to 5 percent. These soils formed in mixed fan alluvium derived from gneiss, granite, and rhyolite. Elevation ranges from 2000 to 3200 feet. The mean annual precipitation is 10 to 13 inches. The mean annual air temperature is 67 to 70 degrees F. The frost-free period is about 240 to 260 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Soledad, Pinaleno, Hayhook, Stagecoach, and Vado soils. The Hayhook, Stagecoach, and Vado soils do not have argillic horizons. Soledad soils average less than 18 percent clay and Pinaleno soils have a calcic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: Topawa soils are used for livestock grazing and wildlife habitat. Vegetation includes triangle bursage, paloverde, ironwood, cacti, bush muhly, black grama and threeawn.
DISTRIBUTION AND EXTENT: Southern Arizona. This series is of moderate extent. MLRA is 40.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Pima County, Arizona; Soil survey of Tohono O'odham Indian Reservation, AZ, Parts of Maricopa, Pima and Pinal Counties; 1993. The name Topawa is from a nearby village.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 2 inches (A horizon)
Argillic horizon - the zone from 2 to 60 inches (Bt1, Bt2, Bt3, Bt4 horizons)
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006.
Revised for the correlation of AZ661, 2/2009, WWJ