LOCATION NACO AZEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, thermic Vertic Paleargids
TYPICAL PEDON: Naco fine sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.) 50 to 70 percent of the surface is covered with gravel and cobbles.
A--0 to 2 inches; brown (7.5YR 5/4) fine sandy loam, brown (7.5YR 4/4) moist; weak granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine and few medium roots; common fine irregular pores; noneffervescent; neutral (pH 6.6); abrupt smooth boundary.
A/B--2 to 8 inches; reddish brown (5YR 5/4) sandy loam, dark reddish brown (5YR 3/3) moist; moderate medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine and fine and few medium roots; common fine irregular and tubular pores; few distinct clay films bridging sand grains; noneffervescent; neutral (pH 6.6); abrupt wavy boundary. (Combined thickness of the A horizons is 2 to 10 inches)
Bt1--8 to 15 inches; reddish brown (5YR 4/4) very cobbly clay, dark reddish brown (5YR 3/3) moist; moderate fine subangular blocky structure; soft, friable, moderately sticky and moderately plastic; common very fine and fine roots; common fine irregular and tubular pores; many distinct clay films on ped faces and on rock fragments; 25 percent gravel and 15 percent cobble; noneffervescent; neutral (pH 6.6); abrupt smooth boundary.
Bt2--15 to 44 inches; dark reddish brown (2.5YR 3/4) very cobbly clay, dark reddish brown (2.5YR 3/4) moist; strong medium and coarse wedge shaped structure; slightly hard, firm, moderately sticky and moderately plastic; many very fine and fine, and common medium roots matted between ped faces; few fine tubular pores; many distinct clay films on ped faces and on rock fragments; common distinct pressure faces; 20 percent gravel and 20 percent cobble; noneffervescent; neutral (pH 6.6); abrupt smooth boundary.
Bt3--44 to 60 inches; yellowish red (5YR 4/6) clay, dark red (2.5YR 3/6) moist; strong medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few fine tubular pores; many distinct clay films on ped faces; noneffervescent; neutral (pH 7.0). (Combined thickness of the Bt horizons is 40 to 60 inches)
TYPE LOCATION: Cochise County, Arizona; located at a latitude of 31 degrees, 32 minutes, 15 seconds North and longitude of 109 degrees, 59 minutes, 55 seconds West; 100 feet north and 2,800 feet west of the southeast corner of section 3, T. 22 S., R. 23 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. Ustic aridic soil moisture regime.
Soil Temperature: 65 to 69 degrees F.
Rock fragments: 35 to 65 percent gravel and cobble
Reaction: neutral to slightly alkaline
Clay content: greater than 35 percent
A horizon
Hue: 5YR, 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 or 4, dry or moist
Texture: sandy loam, fine sandy loam
Bt horizon
Hue: 2.5YR, 5YR
Value: 3 or 4, dry or moist
Chroma: 3 through 6, dry or moist
Texture: clay loam, clay
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Naco soils are on high fan terraces at elevations of 4,400 to 5,000 feet. Slopes range from 1 to 5 percent. These soils formed in fan alluvium from quartz, sandstone and arkose. The mean annual precipitation is 12 to 16 inches and occurs as thunderstorms during July to September and as gentle rains during December and January. The mean annual air temperature is 60 to 67 degrees F. The frost-free period is 180 to 230 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ruins, Nolam, Libby, Buntline, and Keysto soils. Ruins and Libby soils contain less than 35 percent rock fragments. Nolam soils contain less than 35 percent clay. Buntline soils have a hardpan. Keysto soils have less than 18 percent clay.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; very slow permeability.
USE AND VEGETATION: Used for livestock grazing and wildlife habitat. Vegetation includes sideoats grama, curly mesquite, vine mesquite, shrubby buckwheat, ocotillo, mesquite, range ratany and false mesquite.
DISTRIBUTION AND EXTENT: Southern Arizona. Naco soils are of moderate extent. MLRA is 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Cochise County, Arizona; Soil survey of Cochise County, AZ, Douglas-Tombstone Part; 1996.
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 8 to 60 inches (Bt1, Bt2, Bt3 horizons)
Pale feature - Abrupt textural change at 8 inches
Soil Taxonomy Second Edition, 1999