7. Description of the Mapping Units of the Arizona General Soil Map

7.2.1. Hyperthermic Arid Soils

FIGURE 42. Representative Hyperthermic Arid Soils Soilscape and Profiles (D. M. Hendricks)

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FIGURE 43. Geographic Distribution of Hyperthermic Arid (HA) Soils in Arizona (D. M. Hendricks)

HA Hyperthermic Arid Soils

Hyperthermic Arid Soils have mean annual soil temperatures of 22 C (72 F) or higher. The difference between mean summer and mean winter temperatures is greater than 5 C (9 F) at a depth of 50 cm (20 in) or at the soil-bedrock interface in shallow soils. These soils receive less than 250 mm (10 in) mean annual precipitation. Hyperthermic Arid Soils are at the lower elevations in western and southwestern Arizona. They cover about 8,198,860 ha (20,259,100 ac), 27 percent of Arizona.

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HA1 Torrifluvents Association

Deep, stratified, coarse to fine-textured, nearly level to gently sloping soils on floodplains and lower alluvial fans.

• Soil Classification Typic Torrifluvents
• Percent Slope none to 5
• Elevation 30 to 760 m (100 to 2,500 ft)
• Mean Annual Precipitation 80 to 250 mm (3 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 40 to 70
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 27 to 32 C (80 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 255 to 320
• Area and Percent of State 1,928,400 ha (4,765,000 ac), 6.5
• Land Uses irrigated cropland and pasture, rangeland and urban

This association consists of well-drained to somewhat excessively drained soils formed in sandy to clayey recent mixed alluvium on the floodplains and adjacent lower alluvial fans of the lower Santa Cruz, Gila, Salt and Colorado rivers and their major tributaries.

The major Torrifluvents in this map unit include Gilman soils, 20 percent; Antho soils, 20 percent; Vint soils, 15 percent; and Valencia soils, 15 percent. Other similar soils that may be dominant in some areas include Estrella, Avondale, Glenbar, Trix, Holtville, Kofa, Indio, Pimer, Laguna and Gadsden. They constitute about 20 percent of this association. Minor coarse-textured soils and medium and moderately fine-textured soils that are moderately deep over coarse-textured material are about 5 percent of this unit. Included are Carrizo, Brios, Agualt and Maripo and riverwash.

All of the soils in this association are subject to seasonal, brief flooding unless protected. Runoff is slow and the hazard of erosion is usually slight except along entrenched streams where soils are subject to bank cutting, piping and gullying.

About 30 percent of the major irrigated croplands in Arizona are in this association. The principal crops are cotton, grain sorghum, small grains, alfalfa, sugar beets, pasture grasses, vegetables and citrus.

Desert rangeland has low carrying capacity. The native vegetation is mesquite, catclaw, cresosotebush, cacti, bursage, ironwood, arrowweed, saltbush and annual grasses and weeds. Riparian vegetation along major streams includes cottonwood, paloverde, desertwillow and tamarisk, which provide shade for livestock and habitat for many desert wildlife species.

Phoenix and several towns and metropolitan areas are on these soils. Flooding potential is the major limitation of these soils. The permeability of the Valencia soil and the included Estrella, Avondale, Glenbar, Trix, Pimer and Gadsden soils is too limited for septic tank disposal fields. The excessive permeability of the Vint, Antho and included Carrizo, Brios, Agualt and Maripo soils prohibits their use for water retention structures.

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HA2 Casa Grande-Mohall-La Palma Association

Deep and moderately deep, moderately fine-textured, nearly level soils on valley plains.

• Soil Classification
  • Typic Natrargids
  • Typic Haplargids
  • Typic Durargids
• Percent Slope none to 2
• Elevation 240 to 490 m (800 to 1,600 ft)
• Mean Annual Precipitation 150 to 250 mm (6 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 50 to 60
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 250 to 300
• Area and Percent of State 225,420 ha (557,000 ac), 0.8
• Land Uses irrigated cropland, desert rangeland, wildlife habitat and building sites

This association of well-drained soils formed in mixed old alluvium is on valley plains and lower slopes.

Casa Grande soils make up about 35 percent of the map unit, Mohall soils 30 percent, La Palma soils 10 percent, Harqua soils 10 percent and minor soils 15 percent. The minor soils are mostly Tremant, Toltec, Vecont, Laveen and Gilman.

Low amounts of forage for livestock and wildlife are in this unit. The native vegetation is creosotebush, mesquite, paloverde, bursage, cacti and annual weeds and grasses. Supplemental grazing is provided in wet years by the annual grasses and forbs.

Most of the irrigated cropland is on Mohall soils and Casa Grande and Harqua soils that have been reclaimed by leaching. The principal crops are cotton, small grains, grain sorghum, alfalfa and pasture grasses.

Nonirrigated soils have low potential for use as rangeland wildlife habitat. Irrigated soils have good potential for use as openland wildlife habitat.

Factors limiting urban development on these soils are slow permeability, high lime zones in the subsoils, moderate depth to hardpan in La Palma soils, and high salinity and sodium in Casa Grande, La Palma and Harqua soils.

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HA3 Mohall-Vecont-Pinamt Association

Deep, moderately fine and fine-textured and gravelly, moderately fine-textured, nearly level to gently sloping soils on valley plains.

• Soil Classification Typic Haplargids
• Percent Slope mostly less than 2; some to 8
• Elevation 240 to 760 m (800 to 2,500 ft)
• Mean Annual Precipitation 150 to 280 mm (6 to 11 in)
• Winter Precipitation as the Percentage of Annual Precipitation 45 to 60
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 230 to 300
• Area and Percent of State 350,070 ha (865,000 ac), 1.2
• Land Uses desert rangeland and wildlife habitat; some irrigated cropland and homesites

This association of well-drained soils formed in mixed old alluvium on broad valley plains.

Mohall soils make up about 25 percent of the association. Vecont, Pinamt and Tremant soils each represent 20 percent, and minor soils 15 percent. The minor soils include small, intermixed areas of Laveen, Ebon, Contine and Rillito, and narrow bodies of Torrifluvents along the drainageways.

Most of the native vegetation is paloverde, mesquite, creosotebush, ironwood, cacti, bursage and annual weeds and grasses.

Low amounts of forage for livestock and wildlife grow in the unit. Supplemental grazing is provided in wet seasons by annual grasses and forbs.

Mohall soils are well suited for growing arid-adapted crops when irrigation water is available. Slow intake and permeability of Vecont soils require careful water management. Tremant and Pinamt soils usually are not cultivated.

Factors limiting the potential of these soils for homesites are the moderately slow or slow permeability for use as septic tank absorption fields, high shrink-swell in Vecont soils and moderate shrink-swell in Mohall and Tremant soils. The gravelly, high-lime substratum material of the Tremant and Pinamt soils is poor for use as topsoil or landfill cover.

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HA4 Gunsight-Rillito-Pinal Association

Deep and shallow, limy, gravelly, medium and moderately coarse-textured, nearly level to strongly sloping soils on alluvial surfaces and valley plains.

• Soil Classification
  • Typic Calciorthids
  • Typic Durorthids
  • Typic Paleorthids
• Percent Slope mostly none to 5; some to 15 or more
• Elevation 120 to 760 m (400 to 2,400 ft)
• Mean Annual Precipitation 100 to 250 mm (4 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 55 to 65
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 255 to 320
• Area and Percent of State 832,470 ha (2,057,000 ac), 2.8
• Land Uses mostly desert rangeland and wildlife habitat; some homesites

This association of well-drained soils is on broad, shallowly dissected alluvial fans and valley slopes. The soils formed in calcareous, old mixed alluvium derived from volcanic rocks, schist, limestone and granite.

Gunsight and Rillito soils each constitute about 30 percent of this association. Pinal soils cover about 15 percent, Cavelt soils 10 percent and other minor soil inclusions 15 percent. The principal minor soils are Ajo, Cipriano, Laveen, Perryville, Ligurta, Cristobal and Harqua along with small areas of rock outcrop and Torrifluvents in the drainageways. Areas of these soils are in the Organ Pipe National Monument.

The soils produce little forage for livestock and wildlife. Native vegetation consists of widely spaced paloverde, mesquite, cacti, creosotebush, bursage, ironwood, saltbush and annuals. Limited forage is provided by annual grasses and forbs following rainy periods. Larger vegetation along drainageways provides the best wildlife habitat.

Factors limiting these soils for homesite and community uses are high lime and excessive gravel contents. Shallow depth to hardpan and low water capacity in the Pinal and Cavelt soils restrict plant growth. Excavations require the use of heavy equipment in most places. The soils are fairly well suited to support for low buildings without basements. Gunsight and Rillito soils are suitable for use as septic tank absorption fields but have excessive seepage for use as water retention structures.

[page 79]

HA5 Laveen-Rillito Association

Deep, medium and moderately coarse-textured, nearly level to gently sloping, limy soils on low alluvial surfaces and valley plains.

• Soil Classification Typic Calciorthids
• Percent Slope mostly none to 3
• Elevation 180 to 550 m (600 to 1,800 ft)
• Mean Annual Precipitation 130 to 250 mm (5 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 60 to 65
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 C)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 250 to 300
• Area and Percent of State 179,080 ha (442,500 ac), 0.6
• Land Uses irrigated cropland, desert rangeland, wildlife habitat and communities

This association of limy, well-drained soils formed in calcareous, old alluvium derived from limestone and other rocks.

Laveen soils make up about 40 percent of the association, Rillito soils 35 percent and minor soils 25 percent. The minor soils are mostly Mohall, Coolidge, Tremant, Perryville, Antho and Gilman.

Irrigated Laveen soils have good and Rillito soils have fair potential for cropland use. Crops are alfalfa, cotton, small grains, grain sorghum, safflower and sugar beets. Lime sensitive plants may show some chlorosis on these soils. Rillito soils require more frequent irrigation due to lower available water capacity.

Nonirrigated areas produce limited forage for livestock and wildlife. Native vegetation consists of sparse stands of creosotebush, saltbush, bursage, mesquite, paloverde, ironwood, cacti and annual weeds, forbs and grasses. Annuals that grow following rainy periods provide supplemental seasonal grazing.

Where irrigated, these soils are good openland wildlife habitat for doves, quail, rabbits, songbirds, rodents, foxes, badgers, coyotes and snakes.

The soils in this association generally have only slight limitations for most community uses such as homesites, septic tank absorption fields, sanitary landfill and excavations. They are somewhat dusty for use as playgrounds, camping sites and picnic areas. Water retention structures such as sewage lagoons and earthen ponds may seep excessively. Substratum materials may cause chlorosis in plants if used as topsoil.

[page 80]

HA6 Lithic Camborthids-Rock Outcrop-Lithic Haplargids Association

Shallow, very gravelly and cobbly, moderately coarse to moderately fine-textured, gently sloping to very steep soils and rock outcrop on hills and mountains.

• Soil Classification
  • Lithic Camborthids
  • Typic Durorthids
  • Lithic Haplargids
• Percent Slope 2 to 60 or more
• Elevation 90 to 1,490 m (300 to 4,900 ft)
• Mean Annual Precipitation 100 to 250 mm (4 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 50 to 65
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 250 to 300
• Area and Percent of State 3,094,130 ha (7,645,500 ac), 10.5
• Land Uses desert rangeland, wildlife habitat, game refuge, military proving grounds and bombing range and recreation; also heavy equipment proving grounds and city and county parks

This association consists of well-drained, shallow soils and rock outcrop on hills and low mountains. The soils formed in materials weathered residually from granitic rocks, schists, volcanic tuffs and conglomerates, basalt and some shale and sandstone.

Lithic Camborthids make up about 20 percent of the association, Typic Durorthids 15 percent, rock outcrop 35 percent, Lithic Haplargids 15 percent and minor soils 15 percent. Lomitas soils are representative of the Lithic Camborthids. Cherioni soils are the dominant Lithic Durorthids and Gachado soils the Lithic Haplargids. The minor soils are mostly Gunsight, Harqua, Rillito, Ligurta, Cristobal and Pinamt. Torrifluvents and Torriorthents are along drainageways.

Rock outcrop tops the mountain ranges as near-vertical ledges, escarpments and pinnacles, and occurs scattered throughout the shallow soils at the lower elevations.

Dominant native vegetation is creosotebush, paloverde, ironwood, ocotillo, bursage, jojoba, range ratany, saguaro and other cacti, bush muhly, big galleta, tridens, Rothrock and black grama, fluffgrass and annuals.

These soils accommodate little livestock grazing due to rockiness and steepness of the terrain and too low rainfall. Parts of the unit are prime habitat for bighorn sheep.

Factors limiting these soils for homesite and other community uses are shallow depth to rock and slopes of more than 8 percent. Rock fragments on the surface limit use for playgrounds, campgrounds and picnic areas. However, some smoother areas can be used for these purposes or the loose rocks may be removed in others. Many areas, such as the Ajo Mountains, are scenic and unique.

[page 81]

HA7 Laveen-Carrizo-Antho Association

Deep, medium-textured, limy and gravelly, moderately coarse and coarse-textured, nearly level to moderately sloping soils on floodplains and dissected alluvial surfaces.

• Soil Classification
  • Typic Calciorthids
  • Typic Torriorthents
  • Typic Torrifluvents
• Percent Slope mostly none to 8; some steep slopes
• Elevation 150 to 610 m (500 to 2,000 ft)
• Mean Annual Precipitation 100 to 200 mm (4 to 8 in)
• Winter Precipitation as the Percentage of Annual Precipitation 65 to 70
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 250 to 300
• Area and Percent of State 154,390 ha (381,500 ac), 0.5
• Land Uses rangeland, wildlife habitat, homesites and recreation

This association consists of well-drained and excessively drained soils on dissected old alluvial fans and sandy floodplains. They formed in transported alluvium derived from mixed igneous and sedimentary rocks.

Laveen soils make up about 30 percent of this association, Carrizo soils 25 percent, Antho soils 25 percent and minor soils 20 percent. The minor soils are mostly Rillito, Laguna, Brios, Vint, Gilman, Ligurta, Cristobal and Cavelt, and riverwash.

The native vegetation is a sparse growth of creosotebush, bursage, paloverde, catclaw, filaree, cacti, threeawn and annual weeds and grasses.

These soils produce little forage for livestock and wildlife. Seasonal grazing is possible for short periods following rainy periods. Riparian vegetation along some drainageways furnishes cover and some food for wildlife.

Laveen and Antho soils are good for homesite and other community uses, if protected from flooding. They may be somewhat dusty for use as playgrounds and campgrounds. Carrizo soils have very rapid permeability. They are subject to flooding and excessive seepage prohibits their use for sanitary facilities. They are good potential sources of sand and gravel.

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HA8 Tremant-Coolidge-Mohall Association

Deep, moderately coarse and gravelly, moderately fine-textured, nearly level and gently sloping soils on low fan surfaces and valley plains.

• Soil Classification
  • Typic Haplargids
  • Typic Calciorthids
• Percent Slope mostly none to 2; some to 5
• Elevation 120 to 760 m (400 to 2,500 ft)
• Mean Annual Precipitation 80 to 250 mm (3 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 50 to 65
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 250 to 300
• Area and Percent of State 890,340 ha (2,200,000 ac), 3.0
• Land Uses desert rangeland, wildlife habitat, irrigated cropland, homesites and military reservations

This association consists of well-drained soils in broad valleys and adjacent lower alluvial fans. The soils formed in old mixed alluvium derived from igneous and calcareous sedimentary rocks.

Tremant soils make up about 40 percent of this association, Coolidge soils 15 percent, Laveen soils 15 percent and Mohall soils 15 percent. Included in the mapping unit are large areas of Valencia, Rillito and Pinamt soils. Also included in the unit are a few low hills and mountains that have rocky, shallow soils and areas of moderately coarse-textured recent stratified alluvial soils in drainageways. The minor soils make up about 15 percent of the association.

Nonirrigated areas provide some forage for livestock and wildlife. The vegetation consists of creosotebush, scattered paloverde, mesquite and ironwood, saltbush, bursage, cacti and annuals. Limited grazing of annual grasses is possible following wet seasons. Wildlife habitat is mostly along drainageways.

Only small areas are irrigated cropland. They produce alfalfa, small grain, grain sorghum and other arid-adapted crops. Tremant and Coolidge soils are somewhat droughty.

Factors limiting these soils for homesite and community uses are the moderately slow permeability and moderate shrink-swell of the Tremant and Mohall soils. Laveen and Coolidge soils generally are well suited for building sites and sanitary facilities. The limy substrata of all of these soils are poor for topsoil and landfill cover. Denuded areas are dusty.

[page 83]

HA9 Harqua-Perryville-Gunsight Association

Deep, gravelly, moderately fine-textured, and gravelly, limy, medium-textured, nearly level to moderately sloping soils on old fan surfaces.

• Soil Classification
  • Typic Haplargids
  • Typic Calciorthids
• Percent Slope mostly 1 to 8; some to 15
• Elevation 90 to 460 m (300 to 1,500 ft)
• Mean Annual Precipitation 80 to 200 mm (3 to 8 in)
• Winter Precipitation as the Percentage of Annual Precipitation 55 to 65
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 22 to 27 C (72 to 80 F)
• Frost-Free Days 250 to 300
• Area and Percent of State 394,180 ha (974,000 ac), 1.3
• Land Uses wildlife habitat and military proving grounds; some livestock grazing and building sites

This association consists of well-drained, gravelly soils in broad intermountain valleys. They formed in old alluvium derived from volcanic and calcareous sedimentary rocks. Many areas are saline and sodic.

Harqua soils make up about 35 percent of the mapping unit, Perryville soils 25 percent, Gunsight soils 20 percent and minor soils 20 percent. The minor soils are mostly Coolidge, Rillito, Ligurta and Cristobal and small, rocky areas of Lomitas and Cherioni.

Parts of the unit are in the Kofa and Cibola National Wildlife refuges. The dominant native vegetation is a sparse cover of creosotebush, saltbush, bursage, cholla and other cacti, and annual grasses and weeds.

The major limitations of these soils for community uses are moderate to high gravel content of all soils, high salt and alkali content and moderate shrink-swell in Harqua soils and high lime content of the Perryville and Gunsight soils. Perryville and Gunsight soils are suitable sites for low buildings and local roads, and for use as roadfill. The soils are poor for topsoil due to high lime and gravel content. Dust may be a problem in denuded and disturbed areas.

[page 84]

HA10 Superstition-Rosita Association

Deep, coarse-textured, nearly level and undulating soils on terraces.

• Soil Classification
  • Typic Calciorthids
  • Typic Torripsamments
• Percent Slope mostly none to 2; some to 15
• Elevation 30 to 305 m (100 to 1,000 ft)
• Mean Annual Precipitation 80 to 150 mm (3 to 6 in)
• Winter Precipitation as the Percentage of Annual Precipitation 60 to 65
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 23 to 26 C (74 to 79 F)
• Frost-Free Days 280 to 320
• Area and Percent of State 150,390 ha (371,600 ac), 0.5
• Land Uses irrigated cropland, urban and military

This association consists of somewhat excessively drained soils.

Superstition soils make up about 60 percent of the association and Rositas soils 20 percent. The remaining 20 percent includes intermixed areas of Coolidge, Rillito and Harqua soils and a few small areas of rocky buttes and sand dunes.

The natural vegetation consists of widely spaced creosotebush, big galleta, white bursage, turkshead and annual grasses and forbs.

The irrigated crops grown are mostly alfalfa, citrus and a few dates. Numerous frequent irrigations are required for these crops and much of the water applied percolates to the aquifer. Where they are used, new methods of irrigation such as drip or bubbler irrigation have reduced water losses. Cover crops and windbreaks usually are necessary while establishing crops to prevent soil loss by wind erosion.

Factors limiting the potential of these soils for community uses are droughtiness, blowing soil, excessive seepage, loose sandy surfaces and soil caving in excavations. These limitations can be partially overcome by special measures such as windbreaks, drip irrigation and soil stabilization.

7.2.2. Thermic Arid Soils

FIGURE 44. Representative Thermic Arid Soils Soilscape and Profiles (D. M. Hendricks)

[page 86]

FIGURE 45. Geographic Distribution of Thermic Arid (TA) Soils in Arizona (D. M. Hendricks)

TA Thermic Arid Soils

Thermic Arid Soils have mean annual soil temperatures of 15 to 22 C (59 to 72 F). The difference between mean summer and mean winter temperatures is greater than 5 C (9 F) at 50 cm (20 in) or at the soil-bedrock interface in shallow soils. The mean annual precipitation associated with these soils falls between 130 to 250 mm (5 to 10 in). These soils are primarily at low to intermediate elevations in northwestern Arizona as well as along and in the Grand Canyon. Thermic Arid Soils cover about 2,263,240 ha (5,592,400 ac), or 8 percent of Arizona.

[page 87]

TA1 Tottiorthents-Camborthids-Rock Our-Crop Association

Shallow and moderately deep soils and rock outcrop of the canyons, cliffs and mesas.

• Soil Classification
  • Torriorthents
  • Camborthids
• Percent Slope 5 to vertical, some to 1,820 m (6,000 ft)
• Elevation 360 to 2,430 m (1,200 to 8,000 ft)
• Mean Annual Precipitation mostly 150 to 250 mm (6 to 10 in); range is 150 to 500 mm (6 to 20 in)
• Winter Precipitation as the Percentage of Annual Precipitation 60 to 65
• Mean January Air Temperature -1 to 7 C (30 to 45 F)
• Mean July Air Temperature 21 to 27 C (70 to 80 F)
• Mean Annual Soil Temperature mostly 15 to 22 C (59 to 72 F); range is 8 10 24 C (47 to 75 F)
• Frost-Free Days 90 to 340
• Area and Percent of State 779,690 ha (1,926,600 ac), 2.7
• Land Uses recreation, wildlife habitat and some cropland

This association consists primarily of the Grand Canyon area and the major tributaries to the Colorado River. These are shallow and moderately deep, moderately sloping to extremely steep, gravelly, cobbly and stony, moderately coarse to moderately fine-textured soils developed in colluvial and on residual materials such as limestone, sandstone and shale bedrock.

Torriorthents make up about 65 percent of this association, Camborthids about 15 percent and rock outcrop about 15 percent. About 5 percent of the mapping unit is Ustorthents, recent alluvial soils along the tributary drainageways and the Colorado River, very steep talus materials and water, including the Colorado River and the Arizona portions of Lake Mead and Lake Powell.

The contrasting hues of reds, grays and whites and the vastness of the relief formed by millions of years of geologic erosion make this area one of unparalleled scenic grandeur. Recreation activities include hiking, camping, boating and fishing. Most of the area is in the Lake Mead National Recreational Area and the Grand Canyon National Monument, both administered by the National Park Service. Several campgrounds and resorts are in the area. The Havasupai Indians farm a small area near the bottom of the Grand Canyon. Vegetation ranges from desert shrubs in the hot, arid inner canyon to juniper and pine at the higher elevations.

Factors limiting the potential of these soils for development of homesites or campgrounds are the shallow depths to bedrock and the steep slopes.

[page 88]

TA2 Anthony-Vinton-Agua Association

Deep, medium to coarse-textured, nearly level to gently sloping soils on floodplains and low alluvial fans.

• Soil Classification Typic Torrifluvents
• Percent Slope none to 5
• Elevation 610 to 1,220 m (2,000 to 4,000 ft)
• Mean Annual Precipitation 130 to 250 mm (5 to 10 in)
• Winter Precipitation as the Percentage of Annual Percipitation 60 to 70
• Mean January Air Temperature 4 to 7 C (40 to 45 F)
• Mean July Air Temperature 24 to 29 C (75 to 85 F)
• Mean Annual Soil Temperature 15 to 22 C (59 to 72 F)
• Frost-Free Days 200 to 275
• Area and Percent of State 448,210 ha (1,107,500 ac), 1.5
• Land Uses rangeland, wildlife habitat and homesites; some irrigated cropland and pasture along Big Sandy River

This association consists of well-drained soils on the floodplains of intermountain valleys. The soils formed in recent mixed alluvium derived from granite and other rocks.

Anthony soils make up about 35 percent of the association, Vinton soils 30 percent and Agua soils 20 percent. Included in the mapping unit are Gila, Glendale, Tobler and Harrisburg soils in drainageways, and small areas of Rillito and Nickel on low fan surfaces. These minor soils make up about 15 percent of the unit.

All of these soils are subject to brief flooding during wet seasons unless protected.

Vegetation is creosotebush, paloverde, mesquite, cacti, catclaw and annual grasses and weeds. Joshua trees grow north of Red Lake and cottonwood and tamarisk grow along Big Sandy River.

The rangeland generally has low carrying capacity due to the low rainfall and the dominance of low-palatability brushy species. Areas that receive runoff from adjacent uplands support vegetation for seasonal grazing. Riparian vegetation along major streams provides good habitat for various wildlife species.

Possible flooding is a severe limitation for homesite and many other community uses. If protected from flooding, these soils are suitable for use as homesites and sanitary facilities. Excessive seepage, however, prohibits their use for water impoundment structures. These soils are somewhat droughty for growing lawns and landscape plants.

[page 89]

TA3 Lithic Torriorthents-Rock Outcrop-Lithic Haplargids Association

Shallow, gravelly and cobbly, moderately sloping to very steep soils and rock outcrop on hills and mountains.

• Soil Classification
  • Lithic Torriorthents
  • Lithic Haplargids
• Percent Slope mostly 30 to 50; range is 5 to 70 or more
• Elevation 670 to 1,730 m (2,200 to 5,700 ft)
• Mean Annual Precipitation 130 to 250 mm (5 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 60 to 70
• Mean January Air Temperature 2 to 10 C (35 to 50 F)
• Mean July Air Temperature 18 to 32 C (65 to 90 F)
• Mean Annual Soil Temperature 17 to 22 C (62 to 72 F)
• Frost-Free Days 200 to 275
• Area and Percent of State 443,510 ha (1,095,900 ac), 1.5
• Land Uses rangeland, wildlife habitat and recreation; some building sites and mines

This association consists of well-drained, shallow soils and rock outcrop on hills and low mountains in hot, arid areas. The soils formed in residuum weathered from granite, gneiss, schist and volcanic rocks, including tuffs.

Lithic Torriorthents (Cellar and House Mountain soils) make up about 35 percent of the association, rock outcrop 30 percent, Lithic Haplargids (Chiricahua and Lehmans soils) 20 percent and minor soils 15 percent. The minor soils are mostly small areas of Lampshire, Moano, Continental, Pinaleno and Tres Hermanos, and narrow bands of moderately coarse and coarse-textured, stratified soils along drainageways.

Dominant native vegetation is paloverde, mesquite, creosotebush, ocotillo, blackbrush, cacti, threeawn, galleta, bush muhly and blue, slender, sideoats and black grama.

Steepness and stoniness of the soils in this association limit livestock grazing to the smoother, less sloping areas. White- and blacktail deer and bighorn sheep are the primary big-game animals of these areas.

Most homesites and recreation areas are on soils adjacent to Lake Mead. The major soils of the association are severely limited for use as building sites due to excessive slopes and shallowness to bedrock. Chiricahua and Lehmans soils also have high shrink-swell.

[page 90]

TA4 Latene-Anthony-Tres Hermanos Association

Deep, moderately coarse to moderately fine-textured, nearly level to moderately steep soils on alluvial fan surfaces and valley plains.

• Soil Classification
  • Typic Calciorthids
  • Typic Torrifluvents
  • Typic Haplargids
• Percent Slope mostly none to 15; some to 30
• Elevation 610 to 1,060 m (2,000 to 3,500 ft)
• Mean Annual Precipitation 150 to 250 mm (6 to 10 in)
• Winter Precipitation as the Percentage of Annual Precipitation 60 to 65
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 17 to 22 C (62 to 72 F)
• Frost-Free Days 210 to 275
• Area and Percent of State 340,270 ha (840,800 ac), 1.2
• Land Uses rangeland and wildlife habitat; some homesites and irrigated cropland

This association consists of well-drained soils on old alluvial fans and valley plains. They formed in mixed alluvium from igneous and calcareous sedimentary rocks.

Latene and Anthony soils each constitute about 30 percent of this association and Tres Hermanos soils 20 percent. Small areas of Cave, Continental, Gila, Mohave, Nickel, Pinaleno and Whitlock soils make up about 20 percent of the mapping unit.

Most of the native vegetation is bursage, creosotebush, galleta, snakeweed, paloverde, cacti and annual grasses and forbs. Forage production is low due to limited rainfall, but annual grasses and forbs provide some grazing following wet seasons. The best wildlife habitat is along drainageways.

These soils have fair to good potential for use as homesites if the following limitations are overcome: Anthony soils are subject to flooding and are moderately droughty; Latene and Tres Hermanos soils have high lime content on the substrate that is poor for topsoil; and some areas of Tres Hermanos soils have excessive slope.

[page 91]

TA5 Paleorthids-Calciorthids-Torriorthents Association

Shallow and deep, gravelly, medium to coarse-textured, limy, gently sloping to moderately steep soils on valley slopes and hills.

• Soil Classification
  • Paleorthids
  • Calciorthids
  • Torriorthents
• Percent Slope 1 to 30; a few near-vertical escarpments
• Elevation 610 to 1,220 m (2,000 to 4,000 ft)
• Mean Annual Precipitation 150 to 300 mm (6 to 12 in)
• Winter Precipitation as the Percentage of Annual Precipitation 60 to 70
• Mean January Air Temperature 2 to 10 C (35 to 50 F)
• Mean July Air Temperature 24 to 32 C (75 to 90 F)
• Mean Annual Soil Temperature 15 to 22 C (59 to 72 F)
• Frost-Free Days 200 to 275
• Area and Percent of State 251,560 ha (621,600 ac), 0.9
• Land Uses rangeland and wildlife habitat; some homesites and recreation near Lake Mead and irrigated cropland along Virgin River

This association consists of well-drained, calcareous soils on valley slopes, mesas and ridges. The soils formed in calcareous, gravelly alluvium derived from sedimentary and volcanic rocks.

Paleorthids make up about 30 percent of the association, Calciorthids 30 percent, Torriorthents 15 percent and minor soils 25 percent. Cave and Morman Mesa soils are the dominant Paleorthids, Nickel the dominant Calciorthid and Arizo the dominant Torriorthent. The minor soils include Arado, Winkel, Tonopah, Flattop, Bitter Spring, Moapa and St. Thomas. Also included are small areas of rock outcrop and narrow bodies of Torrifluvents along drainageways.

The native vegetation is mostly a sparse cover of creosotebush, blackbrush, bursage, Mormon-tea, desert almond, big galleta, Indian ricegrass, cacti, Mohave yucca and annual grasses and forbs.

These soils have low potential for forage production due to low rainfall and shallow soils. The best wildlife habitat is along drainageways.

Factors limiting the potential for use as homesites are shallow depths of the Paleorthids; high lime content of the Paleorthids and Calciorthids; and flooding hazard and droughtiness of the Torriorthents.

7.2.3. Thermic Semiarid Soils

FIGURE 46. Representative Thermic Semiarid Soils Soilscape and Profiles (D. M. Hendricks)

[page 93]

FIGURE 47. Geographic Distribution of Thermic Semiarid (TS) Soils in Arizona (D. M. Hendricks)

TS Thermic Semiarid Soils

Thermic Semiarid Soils have mean annual soil temperatures of 15 to 22 C (59 to 72 F). The difference between mean summer and mean winter temperatures is greater than 5 C (9 F) at a depth of 50 cm (20 in) or in shallow soils at the soil-bedrock interface. These soils receive 250 to 410 mm (10 to 16 in) annual precipitation. Elevations of Thermic Semiarid Soils range from low to intermediate. They cover about 5,966,410 ha (14,742,800 ac), or 20 percent of Arizona.

[page 94]

TS1 Torrifluvents-Torripsamments Association

Deep, moderately coarse and coarse-textured, nearly level to strongly sloping soils on floodplains and low alluvial fans.

• Soil Classification
  • Torrifluvents
  • Torripsamments
• Percent Slope none to 5
• Elevation 1,030 to 1,220 m (3,400 to 4,000 ft)
• Mean Annual Precipitation 200 to 300 mm (8 to 12 in)
• Winter Precipitation as the Percentage of Annual Precipitation 40 to 45
• Mean January Air Temperature 4 to 7 C (40 to 45 F)
• Mean July Air Temperature 27 to 29 C (80 to 85 F)
• Mean Annual Soil Temperature 16 to 21 C (61 to 69 F)
• Frost-Free Days 210 to 250
• Area and Percent of State 19,830 ha (49,000 ac), less than 0.1
• Land Uses rangeland and wildlife habitat

This association consists of well-drained and somewhat excessively drained soils on floodplains and alluvial fans. They formed in recent sandy alluvium derived from igneous and sedimentary rocks.

Coarse, loamy Torrifluvents make up about 40 percent of the association, Torripsamments 40 percent and other fine, loamy Torrifluvents and sandy or gravelly Torriorthents 20 percent.

The vegetation is low-growing, scattered mesquite, saltbush, creosotebush, Mohave yucca, bush muhly, sand dropseed, blue and Rothrock grama and annual grasses and forbs.

The soils have low potential for forage production due to low rainfall and droughtiness of the soils. Many grasses and forbs, however, respond rapidly to any precipitation that falls during the growing season. Care should be taken to avoid overgrazing or disturbing these soils due to creating the hazard of blowing soil.

Factors limiting the potential of these soils for development of homesites are the flood hazards of the Torrifluvents and the very sandy texture of the Torripsamments.

[page 95]

TS2 Torrifluvents Association

Deep, moderately coarse to moderately fine-textured, nearly level to gently sloping soils on floodplains and alluvial fans.

• Soil Classification Typic Torrifluvents
• Percent Slope none to 3
• Elevation 670 to 1,220 m (2,200 to 4,000 ft)
• Mean Annual Precipitation 230 to 300 mm (9 to 12 in)
• Winter Precipitation as the Percentage of Annual Precipitation 40 to 50
• Mean January Air Temperature 4 to 10 C (40 to 50 F)
• Mean July Air Temperature 24 to 29 C (75 to 85 F)
• Mean Annual Soil Temperature 16 to 22 C (60 to 72 F)
• Frost-Free Days 200 to 270
• Area and Percent of State 142,860 ha (353,000 ac), 0.5
• Land Uses irrigated cropland, rangeland, wildlife habitat, urban and recreation

This association consists of well-drained soils formed on recent mixed alluvium on the floodplains of the Santa Cruz, Upper Gila and San Pedro rivers and their tributaries.

Torrifluvents make up about 95 percent of this association and Torriorthents and other soils make up about 5 percent. The major Torrifluvents in this unit are Grabe, Pima and Anthony soils, each of which make up about 25 percent. About 20 percent consists of Comoro, Gila, Vinton, Guest and Glendale soils. Torriorthents and other included soils are mostly Arizo and Brazito soils and riverwash. Any of these soils may be dominant at a given site.

All of these soils are subject to flooding unless protected. Flooding is usually very brief and local. Areas along entrenched streams are subject to soil piping, gullying and bank cutting.

Cropland and community uses in this association require protection from flooding. Irrigated crops include cotton, alfalfa, grain sorghum, small grains, vegetables and pecans. Natural vegetation includes mesquite, saltbush, catclaw, creosotebush, arrowweed, desertwillow, bush muhly, Arizona cottontop, threeawn and annuals. These soils have medium potential for use as rangeland under good management. They have high potential for openland wildlife habitat in irrigated areas and fair potential for rangeland wildlife habitat where nonirrigated.

[page 96]

TS3 Tubac-Sonoita-Grabe Association

Deep, moderately coarse to fine-textured, nearly level to strongly sloping soils of the uplands and drainageways.

• Soil Classification
  • Typic Paleargids
  • Typic Haplargids
• Percent Slope mostly none to 8; some to 15
• Elevation 910 to 1,520 m (3,000 to 5,000 ft)
• Mean Annual Precipitation 250 to 400 mm (10 to 16 in)
• Winter Precipitation as the Percentage of Annual Precipitation 40 to 50
• Mean January Air Temperature 4 to 10 C (40 to 50 F)
• Mean July Air Temperature 24 to 29 C (75 to 85 F)
• Mean Annual Soil Temperature 16 to 22 C (61 to 72 F)
• Frost-Free Days 185 to 265
• Area and Percent of State 736,550 ha (1,820,000 ac), 2.5
• Land Uses rangeland, wildlife habitat, irrigated cropland and some urban

This association consists of well-drained soils on valley plains and wide floodplains in the Santa Cruz, Sulphur Springs and San Simon valleys. The soils formed in mixed old and recent alluvium derived mostly from igneous rocks.

Tubac and the similar Continental soils make up about 50 percent of the association, Sonoita soils 20 percent, Grabe soils 20 percent and minor soils about 10 percent. The minor soils include Comoro, Pima, Guest, Anthony, Pinaleno, Eba, Forrest, McAllister, Anway, Tres Hermanos and Nickel.

Good yields of cotton, grain sorghum, alfalfa, small grain and vegetables are produced when the soils of this association are irrigated. The native vegetation is mostly grass in the higher elevations and desert shrubs and cacti at the lower elevations. Principal grasses are gramas, plains lovegrass, tobosa and annuals. Shrubs are mesquite, whitethorn, catclaw, burroweed, wolfberry and cacti. Paloverde and ironwood occur at lower elevations.

Under good range management, these soils have fair to good potential for the production of livestock forage. Many areas are in poor condition from overgrazing due to their easy accessibility.

Factors limiting the potential of these areas for development of homesites and other community uses are slow permeability and clayey subsoils in the Tubac and Continental soils and the possibility of flooding of Grabe soils. Sonoita soils are well suited for community uses.

[page 97]

TS4 White House-Bernardino-Hathaway Association

Deep, fine-textured and gravelly, moderately coarse to moderately fine-textured, nearly level to moderately steep soils on alluvial fan surfaces and steep side slopes.

• Soil Classification
  • Ustollic Haplargids
  • Aridic Calciustolls
• Percent Slope mostly 1 to 20, but to 50 where Hathaway soils occur
• Elevation 1,030 to 1,550 m (3,400 to 5,100 ft)
• Mean Annual Precipitation 300 to 460 mm (12 to 18 in)
• Winter Precipitation as the Percentage of Annual Precipitation 50 to 60
• Mean January Air Temperature 2 to 7 C (35 to 45 F)
• Mean July Air Temperature 24 to 29 C (75 to 85 F)
• Mean Annual Soil Temperature 15 to 21 C (59 to 70 F)
• Frost-Free Days 160 to 250
• Area and Percent of State 326,920 ha (807,800 ac), 1.1
• Land Uses rangeland, wildlife habitat and some homesites

This association consists of well-drained soils on nearly level to hilly valley plains and dissected old terraces. The soils formed in old alluvium derived from granitic, volcanic and sedimentary rocks.

White House soils make up about 40 percent of the association, Bernardino soils 20 percent, Hathaway soils 20 percent and minor soils 20 percent. The minor soils are mostly Caralampi and small areas of Bonita, Nickel, Pinaleno and Chiricahua and rock outcrop. Narrow bodies of Guest and Pima soil are along drainageways.

The dominant native vegetation is plains lovegrass, beargrass and blue, black, hairy, sideoats and slender grama. Scattered mesquite and cacti, with some oak trees, grow at higher elevations.

This association has some of the best rangeland in the state, and the potential for range improvement is high. It has fair potential for rangeland wildlife habitat.

Factors limiting the potential of the soils for community uses are slow permeability and high shrink-swell in the White House and Bernardino soils and excessive slope and high lime in Hathaway and some Bernardino soils.

[page 98]

TS5 Caralampi-Hathaway Association

Deep, gravelly, moderately coarse to moderately fine-textured, moderately steep to very steep soils on highly dissected old fan surfaces.

• Soil Classification
  • Ustollic Haplargids
  • Aridic Calciustolls
• Percent Slope mostly 20 to 60; range is 10 to 70
• Elevation 910 to 1,520 m (3,000 to 5,000 ft)
• Mean Annual Precipitation 300 to 410 mm (12 to 16 in)
• Winter Precipitation as the Percentage of Annual Precipitation 35 to 45
• Mean January Air Temperature 4 to 10 C (40 to 45 F)
• Mean July Air Temperature 21 to 27 C (70 to 80 F)
• Mean Annual Soil Temperature 16 to 21 C (60 to 70 F)
• Frost-Free Days 170 to 250
• Area and Percent of State 203,360 ha (502,500 ac), 0.7
• Land Uses rangeland and wildlife habitat; some homesites near Nogales

This association consists of well-drained, very gravelly soils on long narrow ridges formed by deep dissection of old fan surfaces. The soils formed in old alluvium derived from igneous and sedimentary rocks.

Caralampi soils make up about 45 percent of the association, Hathaway soils 35 percent and minor soils about 20 percent. The minor soils include White House, Bernardino, Nolam and Signal on uplands and narrow bands of Torrifluvents and Torriorthents along drainageways. The minor soils may be extensive in some areas.

The dominant native vegetation is plains lovegrass, cane and Texas bluestem, calliandra, beargrass, sideoats, blue, black, hairy and slender grama, and scattered mesquite and cacti. Some oak and juniper grow at higher elevations.

Slopes in excess of 30 percent are somewhat steep for grazing by cattle and horses. The good wildlife habitat is provided in drainageways.

The major factors limiting the potential of these soils for community uses are slopes in excess of 15 percent and high gravel content. Hathaway soils are high in lime.

[page 99]

TS6 Lithic Torriorthents-Lithic Haplustolls-Rock Outcrop Association

Shallow, cobbly and gravelly, strongly sloping to very steep soils and rock outcrop on hills and mountains.

• Soil Classification
  • Lithic Torriorthents
  • Lithic Haplustolls
• Percent Slope mostly 20 to 50; range is 10 to 70
• Elevation 760 to 1,760 m (2,500 to 5,800 ft)
• Mean Annual Precipitation 250 to 510 mm (10 to 20 in)
• Winter Precipitation as the Percentage of Annual Precipitation 35 to 60
• Mean January Air Temperature 2 to 10 C (35 to 50 F)
• Mean July Air Temperature 21 to 29 C (70 to 85 F)
• Mean Annual Soil Temperature 15 to 22 C (59 to 72 F)
• Frost-Free Days 160 to 260
• Area and Percent of State 2,040,090 ha (5,041,000 ac), 6.9
• Land Uses wildlife habitat, rangeland, recreation and mining of copper lead, zinc, silver and gold

This association consists of well-drained, shallow soils and rock outcrop on semiarid, mid-elevation hills and mountains. The soils formed in residuum weathered from many rocks including granite, gneiss, rhyolite, andesite, tuffs, limestone, sandstone and basalt.

Lithic Torriorthents make up about 30 percent of the association, Lithic Haplustolls 25 percent, rock outcrop about 25 percent and Haplargids, other minor soils and Torrifluvents along drainageways, about 20 percent.

The Lithic Torriorthents include House Mountain, Cellar, Retriever, Courthouse, St. Thomas and Schrap series. The Lithic Haplustolls include Lampshire and Mabray soils and similar soils such as Atascosa and Romero. The dominant included Haplargids are Anklam, Chiminea, Chiricahua, Lehmans, Graham, Deloro and Oracle. Other minor soils include Pantano, Pinaleno, Caralampi and Nickel.

Parker Canyon, Arivaipa, Pena Blanca and Patagonia lakes are within areas bounded by this association. The native vegetation varies with elevation and precipitation. At lower elevations the dominant vegetation is paloverde, mesquite, whitethorn, catclaw, jojoba, calliandra, saguaro and other cacti and some grasses. At higher elevations grow many more perennial grasses including Arizona cottontop, cane and Texas bluestem, plains lovegrass, green sprangletop, wolftail and blue, hairy, black, sideoats and slender grama and many others. Oak and juniper may grow above 1,220 m (4,000 ft), but paloverde and saguaro do not grow at this elevation.

Smoother areas of this association have good potential for livestock grazing. The steeper, stonier areas are little used by domestic livestock, but they are good habitat for deer and, in some areas, bighorn sheep.

Factors limiting the potential of these areas for community uses are steep slopes, shallow depth to bedrock and rock fragments on the surface. Selected areas are suitable for campgrounds, picnic areas and pack trails.

[page 100]

TS7 White House-Caralampi Association

Deep, fine-textured and gravelly, moderately fine-textured, gently to moderately sloping soils on old alluvial fan surfaces.

• Soil Classification Ustollic Haplargids
• Percent Slope mostly 2 to 8; some to 15
• Elevation 760 to 1,340 m (2,500 to 4,400 ft)
• Mean Annual Precipitation 300 to 410 mm (12 to 16 in)
• Winter Precipitation as the Percentage of Annual Precipitation 55 to 60
• Mean January Air Temperature 7 to 10 C (45 to 50 F)
• Mean July Air Temperature 29 to 32 C (85 to 90 F)
• Mean Annual Soil Temperature 18 to 21 C (64 to 70 F)
• Frost-Free Days 240 to 270
• Area and Perc