LOCATION CUERDA AZEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, hyperthermic Fluventic Haplocambids
TYPICAL PEDON: Cuerda fine sandy loam - cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 9 inches; pale brown (10YR 6/3) fine sandy loam, brown (7.5YR 5/4) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine roots; common medium irregular pores; slightly effervescent; moderately alkaline (pH 8.2); abrupt smooth boundary. (2 to 12 inches thick)
Bw1--9 to 16 inches; pale brown (10YR 6/3) very fine sandy loam, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common fine roots; common fine irregular pores; slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (4 to 10 inches thick)
Bw2--16 to 30 inches; light brown (7.5YR 6/4) very fine sandy loam, brown (7.5YR 5/4) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; few fine roots; few fine irregular pores; slightly effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (6 to 18 inches thick)
Bk--30 to 60 inches; light brown (7.5YR 6/4) weakly stratified loam, brown (7.5YR 4/4) moist; massive; slightly hard, firm, slightly sticky and slightly plastic; few very fine roots; common calcium carbonate accumulations and coatings in pores and root channels; common fine irregular pores; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Pinal County, Arizona; 1950 east and 2000 feet south of the northwest corner of section 11, T. 5 S., R. 2 E.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually dry, intermittently moist in some part of the soil moisture control section during July - August and December - January. Driest during May and June. Typic aridic soil moisture regime.
Rock fragments - Averages less than 3 percent; some pedons have as much as 10 percent in any one subhorizon. Highly variable from subhorizon to subhorizon in some pedons.
Organic matter - Less than 1 percent; decreases irregularly with depth
Salinity- nonsaline to strongly saline
Sodicity- nonsodic to strongly sodic
Calcium carbonate - Slightly to violently effervescent throughout; secondary calcium carbonate as fillings and masses in the lower part. Calcium carbonate equivalent is less than 6 percent.
A Horizon
Hue: 7.5YR, 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4 dry, 4, 5 or 6 moist
B Horizon
Hue: 7.5YR, 10YR
Value: 5 or 6 dry, 4 or 5 moist
Texture: Very fine sandy loam, loam; some pedons have thin strata of finer or coarser textured material
Stratification - Weakly stratified within and between horizons; usually more finely stratified in the upper part
Reaction - Slightly to strongly alkaline
Buried horizons - Buried argillic horizons occur below 40 inches in some pedons
COMPETING SERIES: These are the Valencia (AZ) and Why (AZ) series. Valencia soils have a buried argillic horizon within 40 inches. Why soils are dominantly fine sandy loam and sandy loam in the particle-size control section.
GEOGRAPHIC SETTING: Cuerda soils are on alluvial fans and flood plains. Elevations range from 300 to 2000 feet. Slopes range from 0 to 3 percent. These soils formed in stratified and mixed alluvium that includes volcanic, granitic, metamorphic and sedimentary rock. The climate is hot, arid continental. The mean annual precipitation is 4 to 10 inches, occurring as summer thunderstorms and gentle winter rain. The mean annual air temperature is 69 to 76 degrees F. The frost-free period is 240 to 325 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Valencia and Why soils and the Coolidge, Dateland, Gilman, Gunsight, Laveen, Pinamt and Rillito soils. Coolidge, Gunsight, Laveen, Pinamt and Rillito soils have a calcic horizon. Dateland soils do not have an irregular decrease in organic matter. Gilman soils are stratified and do not have a cambic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability; receives runoff from slopes above. Flooding is occasional, shallow and very brief. In undisturbed areas, the proximal end of alluvial fans flood more often than the distal end.
USE AND VEGETATION: Irrigated areas are used for the production of alfalfa, cotton and small grains. Native areas are used for limited livestock grazing. The vegetation is creosotebush, wolfberry, mesquite and cacti. Annual plants are Indianwheat grass, filaree and sixweeks grama.
DISTRIBUTION AND EXTENT: Southern Arizona. Cuerda soils are inextensive.
MLRA is 40.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Pinal County, Western Part, Arizona; 1984.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 9 inches (A horizon)
Cambic horizon - The zone from 9 to 30 inches (Bw1, Bw2 horizons)
Secondary calcium carbonate - The zone from 30 to 60 inches
Classified according to Soil Taxonomy Second Edition, 1999