Soil Survey of San Luis Obispo County, California, Carrizo Plain Area

United StatesDepartment ofAgriculture

NaturalResourcesConservationService

In cooperation with theUnited States Departmentof the Interior, Bureau ofLand Management; theUniversity of California,Agricultural ExperimentStation; and the UpperSalinas-Las TablasResource ConservationDistrict

Soil Survey ofSan Luis ObispoCounty, California,Carrizo Plain Area

General Soil Map

The general soil map, which is a color map, shows the survey area divided into groups of associated soils calledgeneral soil map units. This map is useful in planning the use and management of large areas.

To find information about your area of interest, locate that area on the map, identify the name of the map unit in thearea on the color-coded map legend, then refer to the section General Soil Map Units for a general description ofthe soils in your area.

Detailed Soil Maps

The detailed soil maps can be useful in planning the use andmanagement of small areas.

To find information about your areaof interest, locate that area on theIndex to Map Sheets. Note thenumber of the map sheet and turnto that sheet.

Locate your area of interest onthe map sheet. Note the map unitsymbols that are in that area. Turnto the Contents, which lists themap units by symbol and nameand shows the page where eachmap unit is described.

The Contents shows which tablehas data on a specific land use foreach detailed soil map unit. Alsosee the Contents for sections ofthis publication that may addressyour specific needs.

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How To Use This Soil Survey

Additional information about the Nations natural resources is available onlinefrom the Natural Resources Conservation Service at http://www.nrcs.usda.gov.

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This soil survey is a publication of the National Cooperative Soil Survey, a jointeffort of the United States Department of Agriculture and other Federal agencies,State agencies including the Agricultural Experiment Stations, and local agencies. TheNatural Resources Conservation Service (formerly the Soil Conservation Service) hasleadership for the Federal part of the National Cooperative Soil Survey.

Major fieldwork for this soil survey was completed in 1991. Soil names anddescriptions were approved in 2001. Unless otherwise indicated, statements in thispublication refer to conditions in the survey area in 1991. This survey was madecooperatively by the Natural Resources Conservation Service; the United StatesDepartment of the Interior, Bureau of Land Management; and the University ofCalifornia, Agricultural Experiment Station. The survey is part of the technicalassistance furnished to the Upper Salinas-Las Tablas Resource Conservation District.

Soil maps in this survey may be copied without permission. Enlargement of thesemaps, however, could cause misunderstanding of the detail of mapping. If enlarged,maps do not show the small areas of contrasting soils that could have been shown ata larger scale.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all itsprograms and activities on the basis of race, color, national origin, sex, religion, age,disability, political beliefs, sexual orientation, or marital or family status. (Not allprohibited bases apply to all programs.) Persons with disabilities who require alternativemeans for communication of program information (Braille, large print, audiotape, etc.)should contact USDAs TARGET Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights,Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, D.C.20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunityprovider and employer.

Cover: A seeder in a field of daisies on a hillside on the Carrizo Plain. The Temblor Range is inthe background. (Photograph by Johna Hurl, Bureau of Land Management.)

http://www.nrcs.usda.gov

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Contents

How To Use This Soil Survey .................................. iForeword ................................................................ ixGeneral Nature of the Survey Area .......................... 1

How This Survey Was Made ................................ 9Survey Procedures ............................................ 10

General Soil Map Units ........................................ 13Soils on the Bolson Floor ................................... 13

1. Chicote-Playas ........................................ 132. Yeguas-Pinspring .................................... 14

Soils on Alluvial Flats, Alluvial Fans, FloodPlains, and Terraces .................................... 14

3. Polonio-Padres-Wasioja .......................... 144. San Emigdio-Xerofluvents-Elder ............. 155. Arbuckle-Camatta ................................... 15

Soils on Hills and Mountains .............................. 166. Balcom-Nacimiento ................................. 167. Bellyspring-San Timoteo-San Andreas ... 168. Panoza-Beam-Hillbrick ............................ 179. Aramburu-Temblor-Reward ..................... 1710. Saltos-Tajea-Gaviota ............................. 1811. Aido-Ayar-Hillbrick ................................. 1912. Godde-Xerorthents-Rock outcrop ......... 1913. Semper-Rock outcrop-Muranch ............ 2014. Cieneba-Rock outcrop .......................... 20

Detailed Soil Map Units ....................................... 21100Balcom loam, 50 to 75 percent slopes ..... 22101Balcom-Nacimiento complex, 15 to 30

percent slopes ............................................. 23102Balcom-Nacimiento complex, 30 to 50

percent slopes ............................................. 25103Balcom-Nacimiento complex, 9 to 15

percent slopes ............................................. 27109Capay clay, 0 to 2 percent slopes ............. 28110Capay clay, 2 to 9 percent slopes ............. 29112Calleguas-Balcom complex, 15 to 30

percent slopes ............................................. 30114Calleguas-Nacimiento complex, 9 to 30

percent slopes ............................................. 32120Hillbrick-Rock outcrop complex, 15 to

50 percent slopes ........................................ 34121Hillbrick-Rock outcrop complex, 15 to

75 percent slopes ........................................ 35123Lithic Torriorthents-Semper-Rock

outcrop complex, 50 to 75 percent slopes ... 36

129Kilmer-Hillbrick complex, 9 to 15percent slopes ............................................. 38



134Kilmer-Nacimiento-Aido complex, 30 to60 percent slopes ........................................ 43

140Choice silty clay, 15 to 30 percentslopes .......................................................... 44

149San Emigdio sandy loam, 0 to 2 percentslopes .......................................................... 46

150San Emigdio sandy loam, 2 to 9 percentslopes .......................................................... 47

154San Emigdio loam, 0 to 2 percentslopes .......................................................... 48

155San Emigdio loam, 2 to 9 percentslopes .......................................................... 49

159Sorrento loam, 0 to 2 percent slopes ........ 49160Sorrento loam, 2 to 9 percent slopes ........ 50169Polonio loam, 0 to 2 percent slopes .......... 51170Polonio clay loam, 2 to 9 percent slopes .. 53173Polonio gravelly loam, 2 to 9 percent

slopes .......................................................... 54174Polonio-Thomhill complex, 0 to 2

percent slopes ............................................. 55175Polonio-Thomhill complex, 2 to 9

percent slopes ............................................. 56179Padres sandy loam, 0 to 2 percent

slopes .......................................................... 58180Padres sandy loam, 2 to 9 percent

slopes .......................................................... 58182Oceano loamy sand, 2 to 9 percent

slopes .......................................................... 59190Reward channery loam, 15 to 30

percent slopes ............................................. 61191Reward channery loam, 30 to 50

percent slopes ............................................. 62200Aramburu very channery clay loam,

15 to 30 percent slopes ............................... 63201Aramburu very channery clay loam,

30 to 50 percent slopes ............................... 64202Aramburu very channery loam, 50 to 75

percent slopes ............................................. 65

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204Aramburu-Temblor complex, 30 to 50percent slopes ............................................. 66

205Aramburu-Temblor complex, 50 to 75percent slopes ............................................. 67

218Seaback-Calleguas-Panoza complex,30 to 50 percent slopes ............................... 69

219Xerorthents-Badlands complex, 30 to75 percent slopes ........................................ 71

220Beam-Panoza-Hillbrick complex, 15 to30 percent slopes ........................................ 73



227Beam-Panoza complex, stony, 15 to 50percent slopes ............................................. 78

228Beam-Panoza complex, stony, 50 to 75percent slopes ............................................. 80

229Seaback-San Timoteo complex, 50 to75 percent slopes ........................................ 81

230Padres-Wasioja complex, 2 to 9 percentslopes .......................................................... 82

240Panoza-Beam complex, 15 to 30percent slopes ............................................. 84



248Pyxo-Cochora association, 15 to 30percent slopes ............................................. 88

249Xeric Torriorthents-Badlands complex,30 to 75 percent slopes ............................... 90

250Pyxo-Cochora-Badlands association,15 to 75 percent slopes ............................... 91

251Nacimiento clay loam, 15 to 30 percentslopes .......................................................... 93

252Nacimiento clay loam, 30 to 50 percentslopes .......................................................... 94

261Aido clay, 15 to 30 percent slopes ............ 95262Aido clay, 30 to 50 percent slopes ............ 96263Aido clay, 50 to 75 percent slopes ............ 97270Ayar silty clay, 5 to 9 percent slopes ......... 98271Ayar clay, 15 to 30 percent slopes ............ 99274Ayar-Hillbrick-Aido complex, 15 to 30

percent slopes ........................................... 100

275Ayar-Hillbrick-Aido complex, 30 to 50percent slopes ........................................... 102

280Seaback-Panoza-Jenks complex, 9 to15 percent slopes ...................................... 104



290San Timoteo-San Andreas-Bellyspringcomplex, 15 to 30 percent slopes .............. 110



301Arbuckle sandy loam, 2 to 9 percentslopes ........................................................ 115




306Arbuckle sandy loam, 15 to 30 percentslopes, eroded ........................................... 120

307Arbuckle sandy loam, 30 to 50 percentslopes, eroded ........................................... 121

310Yeguas-Pinspring complex, 0 to 2percent slopes ........................................... 122

311Yeguas-Pinspring complex, 2 to 5percent slopes ........................................... 123

321Thomhill loam, 2 to 5 percent slopes ...... 124330Jenks clay loam, 2 to 9 percent

slopes ........................................................ 125339Arnold-San Andreas complex, 9 to 30

percent slopes ........................................... 126340Arnold-San Andreas complex, 30 to

75 percent slopes ...................................... 128350Cieneba coarse sandy loam, 30 to 75

percent slopes ........................................... 129360Chicote complex, 0 to 2 percent

slopes ........................................................ 131361Chicote complex, 2 to 5 percent

slopes ........................................................ 132362Chicote complex, 5 to 9 percent

slopes ........................................................ 134

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371Semper very fine sandy loam, 30 to50 percent slopes ...................................... 135

372Semper very fine sandy loam, 50 to75 percent slopes ...................................... 136

375Semper-Badlands association, 50 to100 percent slopes .................................... 137

380Muranch-Xerorthents-Rock outcropassociation, 30 to 75 percent slopes ......... 139

388Rock outcrop-Gaviota complex, 30 to75 percent slopes ...................................... 141

391Rock outcrop-Lithic Torriorthentscomplex, 50 to 100 percent slopes ............ 142

401Godde-Xerorthents-Rock outcropcomplex, 30 to 75 percent slopes .............. 144

408Gaviota-San Andreas association,15 to 30 percent slopes ............................. 145

409Gaviota-Saltos-Rock outcrop complex,30 to 75 percent slopes ............................. 147

410Gaviota-Rock outcrop complex, 30 to75 percent slopes ...................................... 148

411Tajea-Saltos complex, 15 to 30percent slopes ........................................... 150

412Tajea-Saltos complex, 30 to 50percent slopes ........................................... 151

420Bellyspring-Saltos-Rock outcropcomplex, 50 to 75 percent slopes .............. 153

430Saucito-Akad-Rock outcrop complex,30 to 75 percent slopes ............................. 155

440Bellyspring-Panoza complex, 9 to 15percent slopes ........................................... 156



443Bellyspring-Panoza-Beam complex,50 to 75 percent slopes ............................. 161

445Bellyspring-Xerorthents-Panozacomplex, 15 to 50 percent slopes .............. 163

450Botella loam, 2 to 9 percent slopes ........ 165460Camatta loam, 5 to 30 percent

slopes ........................................................ 166470Botella sandy loam, 2 to 9 percent

slopes ........................................................ 167474Elder sandy loam, 0 to 2 percent

slopes ........................................................ 168

475Elder sandy loam, 2 to 9 percentslopes ........................................................ 169

480Metz loamy sand, 0 to 5 percentslopes ........................................................ 170

490Wasioja loam, 0 to 2 percent slopes ....... 171491Wasioja sandy loam, 2 to 5 percent

slopes ........................................................ 172495Wasioja-Polonio complex, 2 to 5

percent slopes ........................................... 173497Wasioja-Pinspring-Yeguas complex,

2 to 5 percent slopes ................................. 174512Shimmon fine sandy loam, 30 to 50

percent slopes ........................................... 176520Santa Lucia channery clay loam, 50 to

75 percent slopes ...................................... 177521Santa Lucia channery clay loam, 15 to

30 percent slopes ...................................... 178522Santa Lucia channery clay loam, 30 to

50 percent slopes ...................................... 179531Saltos-Millsholm complex, 15 to 30

percent slopes ........................................... 180561Chanac loam, 9 to 30 percent slopes ..... 182562Chanac loam, 30 to 75 percent

slopes ........................................................ 183900Pits ......................................................... 183905Xerofluvents-Riverwash association,

0 to 2 percent slopes ................................. 184906Xerofluvents, 0 to 2 percent slopes ........ 185908Xerorthents very gravelly, 50 to 75

percent slopes ........................................... 186910Playas ponded ........................................ 187911Playas ..................................................... 188

Use and Management of the Soils .................... 189Crops and Pasture ........................................... 189

Land Capability Classification ...................... 192Major Land Resource Areas ........................ 193Important Farmlands ................................... 194Rangeland ................................................... 194

Recreational Development ............................... 198Wildlife Habitat ................................................. 202Engineering ...................................................... 205

Building Site Development ........................... 206Sanitary Facilities ......................................... 210Construction Materials ................................. 215Water Management ..................................... 216

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Soil Properties .................................................... 219Engineering Index Properties ........................... 219Physical Properties .......................................... 220Chemical Properties ........................................ 221Soil Features .................................................... 222Water Features ................................................ 223

Classification of the Soils ................................. 225Soil Series and Their Morphology ........................ 225

Aido Series....................................................... 225Akad Series ..................................................... 226Aramburu Series .............................................. 227Arbuckle Series ................................................ 227Arnold Series ................................................... 228Ayar Series ...................................................... 229Balcom Series .................................................. 229Beam Series .................................................... 230Bellyspring Series ............................................ 230Botella Series ................................................... 231Calleguas Series .............................................. 232Camatta Series ................................................ 233Capay Series ................................................... 233Chanac Series ................................................. 234Chicote Series.................................................. 235Choice Series................................................... 235Cieneba Series ................................................ 236Cochora Series ................................................ 237Elder Series ..................................................... 237Gaviota Series ................................................. 238Godde Series ................................................... 238Hillbrick Series ................................................. 239Jenks Series .................................................... 239Kilmer Series.................................................... 240Lithic Torriorthents ............................................ 241Metz Series ...................................................... 241Millsholm Series ............................................... 242Muranch Series ................................................ 242Nacimiento Series ............................................ 243Oceano Series ................................................. 243Padres Series .................................................. 244Panoza Series .................................................. 245Pinspring Series ............................................... 245Polonio Series .................................................. 246Pyxo Series ...................................................... 247Reward Series ................................................. 248Saltos Series .................................................... 249

San Andreas Series ......................................... 249San Emigdio Series ......................................... 250Santa Lucia Series ........................................... 250San Timoteo Series .......................................... 251Saucito Series .................................................. 252Seaback Series ................................................ 252Semper Series ................................................. 253Shimmon Series ............................................... 253Sorrento Series ................................................ 254Tajea Series ..................................................... 255Temblor Series ................................................. 255Thomhill Series ................................................ 256Wasioja Series ................................................. 257Xeric Torriorthents ............................................ 258Xerofluvents ..................................................... 258Xerorthents ...................................................... 259Yeguas Series .................................................. 259

Formation of the Soils ....................................... 261Diagnostic Horizons ......................................... 261Soil Forming Factors ........................................ 261

Climate ........................................................ 262Living Organisms ......................................... 262Geologic Influences on the Soils ................. 262

References .......................................................... 265Glossary .............................................................. 267Tables .................................................................. 285

Table 1.Temperature and Precipitation ......... 286Table 2.Freeze Dates in Spring and

Fall ............................................................. 287Table 3.Growing Season .............................. 287Table 4.Acreage and Proportionate Extent

of the Soils ................................................. 288Table 5.Land Capability Classification .......... 290Table 6.Prime Farmland ............................... 299Table 7.Additional Soils of Statewide

Importance ................................................ 299Table 8.Rangeland Ecological Sites,

Productivity, and Potential NaturalVegetation .................................................. 300

Table 9.Index of Common and ScientificPlant Names and Plant Symbols ............... 328

Table 10a.Recreational Development(Part 1) ...................................................... 329

Table 10b.Recreational Development(Part 2) ...................................................... 351

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Issued 2003

Table 11a.Building Site Development(Part 1) ...................................................... 373

Table 11b.Building Site Development(Part 2) ...................................................... 395

Table 12a.Sanitary Facilities (Part 1) ............ 413Table 12b.Sanitary Facilities (Part 2) ............ 430Table 13a.Construction Materials (Part 1) .... 456Table 13b.Construction Materials (Part 2) .... 483

Table 14.Water Management ........................ 500Table 15.Engineering Index Properties ......... 516Table 16.Physical Properties of the Soils ..... 548Table 17.Chemical Properties of the

Soils .......................................................... 568Table 18.Soil Features .................................. 583Table 19.Water Features .............................. 597Table 20.Classification of the Soils ............... 608

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Foreword

This soil survey has been developed by the Natural Resources ConservationService, Americas Private Lands Conservation Agency. The survey containsinformation that affects land use planning and other aspects of natural resourcesconservation in this survey area. It contains predictions of soil behavior for selectedland uses. The survey also highlights soil limitations, improvements needed toovercome the limitations, and the impact of selected land uses on the environment.

This soil survey is designed for many different users. Farmers, ranchers, foresters,and agronomists can use it to evaluate the potential of the soil and the managementneeded for maximum food and fiber production. Planners, community officials,engineers, developers, builders, and home buyers can use the survey to plan landuse, select sites for construction, and identify special practices needed to ensureproper performance. Conservationists, teachers, students, and specialists inrecreation, wildlife management, waste disposal, and pollution control can use thesurvey to help them understand, protect, and enhance the environment.

Various land use regulations of Federal, State, and local governments may imposespecial restrictions on land use or land treatment. The information in this report isintended to identify soil properties that are used in making various land use or landtreatment decisions. Statements made in this report are intended to help the landusers identify and reduce the effects of soil limitations that affect various land uses.The landowner or user is responsible for identifying and complying with existing lawsand regulations.

Great differences in soil properties can occur within short distances. Some soils areseasonally wet or subject to flooding. Some are shallow to bedrock. Some are toounstable to be used as a foundation for buildings or roads. Clayey or wet soils arepoorly suited to use as septic tank absorption fields. A high water table makes a soilpoorly suited to basements or underground installations.

These and many other soil properties that affect land use are described in this soilsurvey. Broad areas of soils are shown on the general soil map. The location of eachsoil is shown on the detailed soil maps. Each soil in the survey area is described.Information on specific uses is given for each soil. Help in using this publication andadditional information are available at the local office of the Natural ResourcesConservation Service or the Cooperative Extension Service.

1

The survey area is in the eastern part of San LuisObispo County (fig. 1). The survey area has a total of563,840 acres, or about 881 square miles. It isbordered on the north and northwest by the PasoRobles Soil Survey Area in San Luis Obispo County,on the northeast and east by Kern County, on thesouth by Santa Barbara County, and on the southwestby the Los Padres National Forest. The Carrizo PlainSoil Survey Area includes the Carrizo Plain and partsof the surrounding Temblor, Caliente, and La Panzamountain ranges. Also included in the northwesternpart of the survey area is part of the adjacent SanJuan Creek watershed, bounded by the TemblorRange on the northeast and the La Panza Range onthe southwest.

The spelling used in this survey follows that usedby the U.S. Geological Survey on topographic maps ofthe area. Local spelling commonly is Carisa,Carissa, Carrissa, or Carrisa. The last spelling isthe most common in local usage (USDI, 1995).Carrizo is the Spanish name for common reed. Thename was applied to the area by 16th-centurySpanish explorers because of the abundance in whichthe plant grew on the fringes of Soda Lake (Hollandand Keil, 1995).

General Nature of the Survey AreaThis section provides general information about the

survey area. It describes history and development;physiography, relief, and drainage; geology; plantcommunities; and climate.

Soil Survey of

San Luis Obispo County, California,Carrizo Plain Area

By Eric N. Vinson and Ken Oster

Fieldwork by Richard F. Johnson, Margy Lindquist, Eric N. Vinson, and Karen L. Wiley

United States Department of Agriculture, Natural Resources Conservation Service,in cooperation withthe United States Department of the Interior, Bureau of Land Management; theUniversity of California, Agricultural Experiment Station; and the Upper Salinas-Las Tablas Resource Conservation District

History and Development

Prepared by Lynn E. Moody, Ph.D., Soil Science Department,California Polytechnic State University, San Luis Obispo,California, and Karen Wiley, soil scientist, Natural ResourcesConservation Service.

The Carrizo Plain Area is an isolated part of SanLuis Obispo County. The area is isolated from thewest by the La Panza Mountains and from the east bythe Temblor Mountains. Because of the ruggedtopography, the early east-west transportation routesbypassed the area, passing instead through theCholame Valley to the north and the Cuyama Valley tothe south. As a result of this physical isolation and thesemiarid to arid climate, the area has always beenonly sparsely populated.

Sites at Tulare Lake and Buena Vista Lake in theSan Joaquin Valley and in the Tehachapi Mountainssuggest that the human prehistory of the area begannear the end of the Pleistocene epoch, about 9,000 to11,000 years ago. The Carrizo Plain may have beennear the interface of three Native American cultures:the Chumash, the Southern Valley Yokuts, and theSalinan (USDI, 1995). Apparently, none of thesecultures had permanent settlements in the area. Theydid, however, establish seasonally occupied villagesand create elaborate pictographs on Painted Rock(Piedra Pintada) near the western edge of the CarrizoPlain (Eichel, 1971).

During the Spanish and Mexican settlement ofCalifornia, which began about 1769, the eastern partof what is now San Luis Obispo County remained

2 Soil Survey

thinly populated. The centers of population werefarther north and westalong the coast and in theSalinas Valleyand were associated with themissions (Eichel, 1971). After 1837, when the missionlands were secularized, people remained near theranchos created from the mission lands. The easternpart of what is now San Luis Obispo County was usedonly for grazing cattle and sheep.

California became a territory of the United Statesin 1848 and was admitted to the Union in 1850. TheCalifornia Land Act of 1851 allowed federal lands tobe bought for speculation with virtually norestrictions. Public lands in California weresurveyed from 1854 to 1856 and sold to the public.Most of the land in the eastern part of San LuisObispo County was in the public domain. Hugetracts were purchased by speculators whocontinued to graze livestock on some tracts andwere not much interested in settling the area.Acquisition of these tracts effectively removed thepossibility of settlement of the land by families(Eichel, 1971).

The Atlantic and Pacific Railroad obtained landrights for much of eastern San Luis Obispo Countyto the eastern edge of the Caliente and La Panza

Rangesby 1866. That land was also withdrawn fromthe possibility of settlement (Eichel, 1971). By 1885,most of the available and accessible land in San LuisObispo County was occupied. Pressure was exertedon the General Land Office to declare the Atlantic andPacific Railroad grants to be forfeited, and these landswere then opened to homesteading and settlement.Favorable lands to the north and west of the CarrizoPlain were then settled rapidly.

During the last quarter of the 1800s, a few peoplebegan to move into the area. The first ranch in theCarrizo Plain was the El Saucito Ranch. It wasoccupied by Chester Brumley, an employee of JamesM. McDonald, one of the large landowners. It was inthe southwestern part of the Carrizo Plain andincluded a residence; land for grazing by cattle andsheep; a eucalyptus planting; and peach, apple, andcherry orchards irrigated from shallow wells. Wheatand barley were dry-farmed for hay.

Homesteads of 160 acres were made availablealong the northeast perimeter of the Carrizo Plain.They were quickly settled and made into self-sufficient farms. Shallow wells were not productiveenough for irrigation, so dry-farming was used toproduce grain for humans, pigs, cows, chickens,and horses. Salt was brought from Soda Lake forcattle and was refined in small amounts for cooking.The main forms of transportation were horsebackand wagon. San Luis Obispo was a 2-day trip bywagon. Small settlements developed at Simmlerand La Panza. This population increase was short-lived, however, because many of the settlers werehard hit by a drought in the 1890s and were forcedto leave. On the Carrizo Plain itself, cattlepredominated and grazed on the tracts owned bythe large landholders. Cattle grazing, being a mobileenterprise, was little affected by the drought (Eichel,1971).

Mining played a small part in the history of easternSan Luis Obispo County. Gold was mined from thestreams flowing east into the San Juan River near LaPanza. It is estimated that $10,000 worth of gold wasextracted from 1877 to 1878. Sodium sulfate wasmined from Soda Lake on the Carrizo Plain from the1890s to the 1930s. A small, temporary settlement forlaborers was established at Soda Lake. Lack ofefficient transportation was a large obstacle to mining.McKittrick, the nearest railhead, was 16 miles away. In1923, a narrow gauge railroad was built from SodaLake to the McKittrick road. Exploratory drilling for oilbegan before 1910. Traces of good-quality oil werediscovered, but not in commercial quantities (Eichel,1971).

Figure 1.Location of San Luis Obispo County, California,Carrizo Plain Area.

San Luis Obispo County, California, Carrizo Plain Area 3

In the early 1900s, irrigation was developed inCamatta Canyon in the northwestern corner of thesurvey area. Irrigated sugar beets, alfalfa, and morerecently, grapes, became important crops. In the1920s and 1930s, advancing farm technology andimproved transportation caused a shift in theagriculture of eastern San Luis Obispo County fromcattle grazing to large-scale grain production. Tractorsmade it feasible to cultivate large acreages of dry-farmed wheat in the Carrizo Plain and barley in thenorth toward the Bitterwater area. The improvedtransportation provided a means to get the grain tomarket. Farming did not by any means, however,completely replace the livestock industry. Beef cattlestill grazed on the hills and on the dry-farmed landafter crops have been harvested. Sheep have alsobeen a part of the livestock industry in the surveyarea. Sheep grazing in the Carrizo Plain areagenerally has been seasonal and migratory (Eichel,1971).

In 1984, the Carrizo Plain Natural Area wasestablished. It is a 180,000-acre reserve acquired andcooperatively managed by the Bureau of LandManagement, The Nature Conservancy, the CaliforniaDepartment of Fish and Game, the U.S. Fish andWildlife Service, the California Energy Commission,oil companies, and other agencies and cooperators.This ecological preserve is noted for flora and faunathat are considered representative of undisturbed,pre-agricultural conditions in this and nearbyCalifornia-interior valleys, including the San JoaquinValley. Specific management objectives arepreserving and enhancing habitat for threatened andendangered species, reintroducing native pronghornantelope and tule elk, protecting cultural resources,and promoting environmental research and education.Threatened and endangered species in the areainclude the giant kangaroo rat, the blunt-nosedleopard lizard, the San Joaquin antelope squirrel, theSan Joaquin kit fox, and several species of plants(USDI, 1995).

Today, the population of the Carrizo Plain area isgreater than in the early days of California. Most ofthe people live on scattered ranches, farms, and smallhomesteads. There is a subdivision in CaliforniaValley on the Carrizo Plain where roads are laid outand lots have been surveyed, but few people livethere. In the 1960s, a service area with a motel,restaurant, service station, air strip, sales office, andcommunity center was built to encouragedevelopment in the California Valley. The areaspopulation has grown over the years but is still farbehind that of the rest of the county.

Physiography, Relief, and Drainage

Prepared by Lynn E. Moody, Ph.D., Soil Science Department,California Polytechnic State University, San Luis Obispo,California, and Eric N. Vinson, soil scientist, Natural ResourcesConservation Service.

The Carrizo Plain Area is within the southern CoastRanges physiographic region. The survey areaconsists of several physiographic units (fig. 2). Theyare the Carrizo Plain (including Soda Lake) in themiddle of the survey area; the Temblor Range to thenortheast; the Caliente Range to the west andsouthwest; the La Panza Range to the west; theElkhorn Plain, which is a much smaller valley than theCarrizo Plain, to the southeast; the San Juan Hills; andthe San Juan Valley and associated tributary canyons.

The Carrizo Plain is a bolson, a nearly level valleythat has internal surface drainage (fig. 3). The valley isabout 40 miles long and 8 miles wide at its widestpoint. Elevation of the valley ranges from 1,900 feet(578 m) at Soda Lake to 2,100 feet (638 m). SodaLake, which is in the middle of the Carrizo Plain, is adesert-type playa and is subject to seasonal flooding.

The Temblor, La Panza, and Caliente Ranges aregenerally rugged mountains that have some rollinghills (fig. 4). Most slopes are steep or very steep, andrunoff is rapid or very rapid. Elevations range from1,600 to 4,300 feet. The highest point in San LuisObispo County is Caliente Mountain, which has anelevation of 5,106 feet. The highest point in theTemblor Range is McKittrick Summit, which has anelevation of 4,332 feet. The highest point in the SanJuan Hills is Freeborn Mountain, which has anelevation of 3,311 feet.

The southwestern slopes of the Temblor Rangedrain into the Carrizo Plain and to the north into SanJuan Creek. The northeastern slopes drain into theSan Joaquin Valley. The northeastern slopes of theCaliente Range and the eastern slopes of the SanJuan Hills drain into the Carrizo Plain. Thenortheastern slopes of the La Panza Range drain intoSan Juan Creek. The western and southwesternslopes of the Caliente Range drain into the CuyamaRiver. The southwestern slopes of the La PanzaRange drain into the Salinas River.

The Elkhorn Plain is a small plain in thesoutheastern part of the survey area. It is orientatedparallel to the Carrizo Plain. It is bounded on thesouthwest by the Panorama Hills, Elkhorn Scarp, andElkhorn Hills (fig. 5). It is bounded on the northeast bythe Temblor Range. It has an elevation of about 2,300to 2,800 feet. At its northwest end, it drains into theCarrizo Plain.

4 Soil Survey

The San Juan Valley is northwest of the CarrizoPlain (fig. 6). The San Juan Valley is bounded on thenortheast by the Temblor Range and the San JuanHills and on the southwest by the La Panza Range. Itis separated from the Carrizo Plain by the San JuanHills. On both sides of San Juan Creek are numerouslarge and small tributary canyons from thesurrounding hills and mountains. Camatta Canyon is alarge tributary at the west end of the survey area. SanJuan Creek flows northwest and eventually joins theEstrella River near Shandon, California.

In the Carrizo Plain, aquifers containing freshground water are in Quaternary alluvium, the

Pleistocene Paso Robles Formation, and the upperPliocene Morales Formation (Kemnitzer, 1967). TheQuaternary alluvium covers most of the basin floorand is up to several hundred feet thick, being thickestat Soda Lake. This formation consists of interbeddedgravel, sands, silts, and clays. It has limitedproductivity. The water may be brackish and of poorquality due to dissolved sodium salts, especially nearSoda Lake (fig. 7).

The Paso Robles Formation is widely distributedthroughout the Carrizo Plain and in most areas iscovered with the younger alluvium. It is exposed in therolling hills at the northeast end of the plain. The Paso

Figure 2.Physiographic map of the Carrizo Plain Area.


Figure 3.Idealized cross-section of the Carrizo Plain showing soil-landscape-geology relationships.

Figure 4.The Temblor Range in winter. (Photograph by Johna Hurl, Bureau of Land Management.)

6 Soil Survey

Robles Formation is more than 3,000 feet thick nearthe San Andreas Fault and thins westward. It slopesfrom west to east and from south to north. It storesand transmits water readily, and wells which tap ithave been very productive. Water contained in thisformation is usually of fair to good quality.

The Morales Formation outcrops over smallareas to the northwest and southeast of the CarrizoPlain. It is widespread in the subsurface. It consistsof gravel, sands, and silts. It ranges in thicknessfrom a few feet to more than 3,000 feet. Most of theground water contained in the Morales Formation isbrackish and of poor quality, but there are pocketscontaining fresher water that is suitable for livestockand irrigation.

Geology

Prepared by Lynn E. Moody, Ph.D., Soil Science Department,California Polytechnic State University, San Luis Obispo,California.

The most prominent and best known geologicalfeature of the survey area is the San Andreas Fault(fig. 8). Many landforms in the survey area areassociated with the San Andreas Fault and areconsidered textbook examples of landforms formedby earth movement (Hill, 1984). The fault passesthrough the foothills of the Temblor Range at thenortheast boundary of the Carrizo Plain. Movementon the southwest side of the fault is in a northwestdirection. The deformation of the land caused bymovement along this fault has shaped the Carrizo

Figure 5.Elkhorn Scarp, which was created by the SanAndreas Fault.

Figure 6.Idealized cross-section of the northwestern part of the survey area, showing soil-landscape-geology relationships.


Plain and its bounding mountain ranges. Alignmentof scarps, ridges, trenches, and valleys show theinfluence of the faulting on the shape of the land.

The San Juan Fault, Big Spring Fault, and MoralesFault pass through the San Juan Hills and the foothillsof the Caliente Range at the southwest and westedges of the Carrizo Plain (Dibblee, 1973; Jennings,1959). These faults are less well known than the SanAndreas Fault, but they also reflect movement of landmasses past each other and have been veryinfluential in shaping the landscapes of the surveyarea. These faults formed the uplifts that separateSan Juan Creek and the Cuyama Valley from theCarrizo Plain.

The Temblor Range and most of the CalienteRange are composed of sedimentary rocks ofupper, middle, and lower Miocene age. These rocksinclude sandstones, shales, conglomerates, andsiltstones that were originally deposited in eitherfresh water or ocean water (Dibblee, 1973). Thenorthwest part of the La Panza Range is composedof granitic rocks (Dibblee, 1973; Jennings, 1959).

Deformation of the land by faulting has causedthe land to be lifted upward. Subsequent watererosion has carved the uplifted land into hillsand mountains. Uplift and erosion are stilloccurring.

The Carrizo Plain is underlain by Pleistoceneaged alluvium, called the Paso Robles Formation,covered in most areas by a layer of youngeralluvium. The sediments were deposited by streamsand flood waters washing material out of themountain ranges, filling in the valleys. Just as upliftand erosion of the surrounding mountainscontinues, the valley continues to fill in withalluvium. The Elkhorn Plain also is underlain byalluvium. The San Juan Valley and its tributarycanyons are also underlain by alluvium that iswashed down from slopes and transported,reworked, and deposited by streams. The valleyfloors are occupied by broad, flat flood plains. Someareas have stream terrace deposits, which are theremnants of ancient flood plains that are nowabandoned by the steadily down-cutting streams.

Figure 7.View of Soda Lake from the south. Water drains across Chicote soils and into the lake. (Photograph by Johna Hurl,Bureau of Land Management.)

8 Soil Survey

Plant Communities

Prepared by Lynn E. Moody, Ph.D., Soil Science Department,California Polytechnic State University, San Luis Obispo,California, and Karen Wiley, soil scientist, Natural ResourcesConservation Service.

Vegetation in the Carrizo Plain Soil Survey areacan be divided into six natural plant communities:Valley and Southern Coastal Grassland, FoothillWoodland, Juniper-Oak Woodland, Chaparral, DesertScrub, and Alkali Sink (Holland and Keil, 1995). Theseplant communities grade into one another, and islandsof one type of community are commonly enclosed inanother.

The Valley and Southern Coastal Grassland plantcommunity is throughout the northern part of the

survey area. It is in areas in and around BitterwaterCreek, Choice Valley, and Camatta Canyon and onthe Carrizo Plain. The vegetation consists of acombination of grasses and forbs, varies widely fromplace to place depending on soil type and climate,and may vary from year to year as rainfall and grazingpatterns change. Wild oats, soft chess, ripgut brome,and foxtail fescue are major annual grasses. Redbrome is found on the more arid sites. Common forbsare California poppy, creamcups, fiddleneck, filaree,lupine, clover, tidytips, clarkia, brodiaea, turkeymullein, and vinegarweed. Scattered Californiabuckwheat occurs in some locations. Needlegrassand other native perennial grasses originallydominated the grassland vegetation. Exotic annualgrasses were introduced in the early 1800s. Heavygrazing reduced the extent of native perennialgrasses and allowed the annual grasses todominate.

The Foothill Woodlands plant community is in thehills bordering the La Panza Range and at thesouthern end of Camatta Canyon. The vegetationconsists of open stands of trees with an understory ofgrass cover. The common trees are foothill pine, blueoak, and live oak on hillsides and California white oakin the lower valleys. Cottonwood and willow grow inriparian areas along and in stream channels. Thisplant community borders the Juniper-Oak Woodland,Chaparral, and Grassland plant communities.

The Juniper-Oak plant community is at the northend of the La Panza Range, southward along the SanJuan River, and at the higher elevations in theTemblor and Caliente Ranges. It consists dominantlyof an open to dense cover of California juniper. Inplaces, it includes blue oak. California buckwheat andgrasses and forbs are also members of the Juniper-Oak community.

The Chaparral plant community consists of adense stand of woody shrubs. It is common on thehills of the La Panza Range along the westernboundary of the survey area. The major shrub ischamise, which occurs either in nearly pure stands orin mixed stands including ceanothus, manzanita,California scrub oak, sage, and other shrubs.Chaparral is a fire-adapted type of plant community. Itsurvives and even thrives after burning. Many shrubspecies can sprout from burls or root crowns. Someannual and a few perennial species germinate onlyafter fire has swept the area.

The Desert Scrub plant community is along thelower slopes of the Temblor Range, especially in thesouth on the Elkhorn Plain and the Panorama Hills. Itis also on the southern slopes of Caliente Mountain. Itconsists of a combination of grasses and scattered

Figure 8.View of the San Andreas Fault from the north.Drainageways are offset by lateral movement of the fault.Padres sandy loam is on the Elkhorn Plain to the left.Beam loam, Panoza loam, Xerorthents, and Badlands areadjacent to the fault. (Photograph by Johna Hurl, Bureauof Land Management.)


shrubs. The shrubs include Morman tea ephedra,saltbush, and California buckwheat. The grassesinclude red brome.

The Alkali Sink plant community is in flat areasaround Soda Lake on the Carrizo Plain. It consists ofsalt-tolerant plants and includes iodinebush andsaltgrass.

Climate

Prepared by the Natural Resources Conservation ServiceNational Water and Climate Center, Portland, Oregon.

The climate tables were created using datacollected mainly at the climate station in Maricopa,California, which is just southeast of the Carrizo Plainin Kern County. Some additional climate informationwas collected from the New Cuyama Fire Stationclimate station. Thunderstorm days, relative humidity,percent sunshine, and wind information wereestimated from the First-Order station at Bakersfield,California.

Table 1 gives data on temperature and precipitationfor the survey area as recorded at Maricopa in theperiod 1961 to 1990. Table 2 shows probable dates ofthe first freeze in fall and the last freeze in spring.Table 3 provides data on the length of the growingseason.

In winter, the average temperature at Maricopa is48.2 degrees F and the average daily minimumtemperature is 38.1 degrees F. The lowesttemperature on record, which occurred at Maricopaon December 6, 1978, was 15 degrees F. In summer,the average temperature is 81.0 degrees F and theaverage daily maximum temperature is 95.4 degreesF. The highest temperature on record, which occurredat Maricopa on July 1, 1950, was 116 degrees F.Temperatures over the Carrizo Plain are a little moreextreme than at Maricopa. The average winterminimum temperatures are around freezing andrecord lowest temperatures are between 0 and 10degrees F. In a typical year, the highest summertemperature is around 105 degrees F and the coldestwinter temperature is between 15 and 25 degrees F.

Growing degree days are shown in Table 1. Theyare equivalent to heat units. During the month,growing degree days accumulate by the amount thatthe average temperature each day exceeds a basetemperature (50 degrees F). The normal monthlyaccumulation is used to schedule single orsuccessive plantings of a crop between the lastfreeze in spring and the first freeze in fall.

The Carrizo Plain is quite dry. The mean annualprecipitation is mostly between 8 and 10 inches. Theareas with the highest terrain have mean annual

precipitation between 10 and 14 inches. The meanannual precipitation at Maricopa is about 6.34 inches.Of this, about 4.83 inches, or 76 percent, usually fallsin February through November. The growing seasonfor most crops falls within this period. The heaviest1-day rainfalls during the period of record were 4.15inches at Maricopa on February 10, 1978, and 3.04inches at New Cuyama on March 19, 1991.Thunderstorms occur on about 3 days each year.

It has snowed only about 5 times in the past 50years at Maricopa. The heaviest 1-day snowfall onrecord was 6.0 inches, recorded on January 22, 1962.At New Cuyama, which is more indicative for snow onthe Carrizo Plain, it snows a little in some winters, butseldom more than 1 or 2 inches at any one time. Theheaviest 1-day snowfall at New Cuyama was 3.8inches in March, 1974. Between 1986 and 1999, itsnowed only once and only briefly.

The average relative humidity in mid-afternoon isabout 35 percent. It ranges from around 60 percent inwinter to less than 20 percent in summer. Humidity ishigher at night, and the average at dawn is about 80percent in winter and 50 percent in summer. The sunshines 96 percent of the time possible in summer andabout 60 percent in winter. The prevailing wind is fromthe northwest. Average wind speed is highest, around8 miles per hour, from April to June.

How This Survey Was MadeThis survey was made to provide information about

the soils and miscellaneous areas in the survey area.The information includes a description of the soils andmiscellaneous areas and their location and adiscussion of their suitability, limitations, andmanagement for specified uses. Soil scientistsobserved the steepness, length, and shape of theslopes; the general pattern of drainage; the kinds ofcrops and native plants; and the kinds of bedrock.They dug many holes to study the soil profile, which isthe sequence of natural layers, or horizons, in a soil.The soil profile extends from the surface down intothe unconsolidated material in which the soil formed.The unconsolidated material is devoid of roots andother living organisms and has not been changed byother biological activity.

The soils and miscellaneous areas in the surveyarea are in an orderly pattern that is related to thegeology, landforms, relief, climate, and naturalvegetation of the area. Each kind of soil andmiscellaneous area is associated with a particularkind of landform or with a segment of the landform. Byobserving the soils and miscellaneous areas in thesurvey area and relating their position to specific

10 Soil Survey

segments of the landform, a soil scientist develops aconcept or model of how they were formed. Thus,during mapping, this model enables the soil scientistto predict with a considerable degree of accuracy thekind of soil or miscellaneous area at a specificlocation on the landscape.

Commonly, individual soils on the landscape mergeinto one another as their characteristics graduallychange. To construct an accurate soil map, however,soil scientists must determine the boundariesbetween the soils. They can observe only a limitednumber of soil profiles. Nevertheless, theseobservations, supplemented by an understanding ofthe soil-vegetation-landscape relationship, aresufficient to verify predictions of the kinds of soil in anarea and to determine the boundaries.

Soil scientists recorded the characteristics of thesoil profiles that they studied. They noted color,texture, size and shape of soil aggregates, kind andamount of rock fragments, distribution of plant roots,reaction, and other features that enable them toidentify soils. After describing the soils in the surveyarea and determining their properties, the soilscientists assigned the soils to taxonomic classes(units). Taxonomic classes are concepts. Eachtaxonomic class has a set of soil characteristics withprecisely defined limits. The classes are used as abasis for comparison to classify soils systematically.Soil taxonomy, the system of taxonomic classificationused in the United States, is based mainly on the kindand character of soil properties and the arrangementof horizons within the profile. After the soil scientistsclassified and named the soils in the survey area,they compared the individual soils with similar soils inthe same taxonomic class in other areas so that theycould confirm data and assemble additional databased on experience and research.

While a soil survey is in progress, samples of someof the soils in the area generally are collected forlaboratory analyses and for engineering tests. Soilscientists interpret the data from these analyses andtests as well as the field-observed characteristics andthe soil properties to determine the expected behaviorof the soils under different uses. Interpretations for allof the soils are field tested through observation of thesoils in different uses and under different levels ofmanagement. Some interpretations are modified to fitlocal conditions, and some new interpretations aredeveloped to meet local needs. Data are assembledfrom other sources, such as research information,production records, and field experience ofspecialists. For example, data on crop yields underdefined levels of management are assembled from

farm records and from field or plot experiments on thesame kinds of soil.

Predictions about soil behavior are based not onlyon soil properties but also on such variables asclimate and biological activity. Soil conditions arepredictable over long periods of time, but they are notpredictable from year to year. For example, soilscientists can predict with a fairly high degree ofaccuracy that a given soil will have a high water tablewithin certain depths in most years, but they cannotpredict that a high water table will always be at aspecific level in the soil on a specific date.

After soil scientists located and identified thesignificant natural bodies of soil in the survey area,they drew the boundaries of these bodies on aerialphotographs and identified each as a specific mapunit. Aerial photographs show trees, buildings, fields,roads, and rivers, all of which help in locatingboundaries accurately.

This survey area was mapped at two levels ofdetail. At the more detailed level, map units arenarrowly defined. Map unit boundaries were plottedand verified at closely spaced intervals. At the lessdetailed level, map units are broadly defined.Boundaries were plotted and verified at widerintervals. The following areas were mapped at themore detailed level: San Juan Valley, Camatta CanyonValley, Shandon Area, Carrizo Plain, and ElkhornPlain. The remaining uplands were mapped at theless detailed level.

The descriptions, names, and delineations of thesoils in this survey area do not fully agree with thoseof the soils in adjacent survey areas, particularly theSoil Survey of the Los Padres National Forest Area,California, and the Soil Survey of Northern SantaBarbara Area, California. Differences are the result ofa better knowledge of soils, modifications in seriesconcepts, or variations in the intensity of mapping orin the extent of the soils in the survey areas.

Survey ProceduresThe general procedures followed in making this

survey are described in the National Soil SurveyHandbook of the Natural Resources ConservationService and the Soil Survey Manual (USDA, 1996a;Soil Survey Division Staff, 1993).

Before the fieldwork began, preliminary boundariesof slopes and landforms were plotted stereoscopicallyon aerial photographs taken in 1978 and enlarged toa scale of 1:24,000. Soil scientists studied U.S.Geological Survey topographic maps, at a scale of1:24,000, to relate land and image features.


Reconnaissance was made by vehicle before thelandscape was traversed on foot.

Sample areas were selected to represent the majorlandscapes in the survey area. These areas wereinvestigated more closely than the rest of the surveyarea. Extensive notes were taken on the compositionof map units in these preliminary study areas. Asmapping progressed, these preliminary notes weremodified and a final assessment of the composition ofthe individual map units was made.

As the traverses were made, the soil scientistsdivided the landscape into landforms or landformsegments based on use and management of the soils.For example, a hill would be separated from adepression and a gently sloping summit from a verysteep back slope of a ridge.

Observations of such items as landform, blown-down trees, vegetation, roadbanks, and animalburrows were made without regard to spacing. Soilboundaries were determined based on soil

examinations, observations, and photo interpretation.The soil material was examined with the aid of a handauger or a spade to a depth of about 6 feet or tobedrock within a depth of 6 feet. The pedonsdescribed as typical were observed and studied inpits that were dug with shovels, spades, orbackhoes.

Samples for chemical and physical analyses andfor analyses of engineering properties were takenfrom representative sites of several of the soils in thesurvey area. The chemical and physical analyseswere made by the National Soil Survey Laboratory,Natural Resources Conservation Service, Lincoln,Nebraska. The results of the analyses are stored in acomputerized data file at the laboratory. A descriptionof the laboratory procedures can be obtained onrequest from this laboratory. The results of thestudies can be obtained from the State office of theNatural Resources Conservation Service at Davis,California.

13

The general soil map with this publication showsbroad areas that have a distinctive pattern of soils,relief, and drainage. Each map unit on the general soilmap is a unique natural landscape. Typically, itconsists of one or more major soils or miscellaneousareas and some minor soils or miscellaneous areas. Itis named for the major soils or miscellaneous areas,known as major components. The components of onemap unit can occur in another but in a differentpattern.

The general soil map can be used to compare thesuitability of large areas for general land uses. Areasof suitable soils can be identified on the map.Likewise, areas where the soils are not suitable canbe identified.

Because of its small scale, the map is not suitablefor planning the management of a farm or field or forselecting a site for a road or building or otherstructure. The soils in any one map unit differ fromplace to place in slope, depth, drainage, and othercharacteristics that affect management.

Soils on the Bolson Floor

1. Chicote-Playas

Very deep, nearly level to moderately sloping,somewhat poorly drained and poorly drained soilsthat formed in fine textured lacustrine sediments andalluvium on the bolson floor

Setting

Landform: The bolson floor of the Carrizo PlainSlope: 0 to 9 percent

Composition

Extent of the map unit in the survey area: 5 percentExtent of the components in the map unit:

Chicote soils63 percentPlayas17 percentMinor soils20 percent

Soil Properties and Qualities

ChicoteDepth class: Very deepDrainage class: Somewhat poorly drainedPosition on landform: Lake plains adjacent to playasParent material: Alluvium from sedimentary rocks;

lacustrine sedimentsTexture of the surface layer: Silty clay loam and silt

loamSlope: Nearly level to moderately sloping

PlayasDepth class: Very deepDrainage class: Poorly drainedPosition on landform: Lowest areas on the bolson

floorParent material: Alluvium from sedimentary rocks;

lacustrine sedimentsSlope: Nearly level

Minor soils Polonio soils on alluvial fans Yeguas soils on alluvial flats and alluvial fans Small areas of slick spots on the nearly levelChicote soils

Use and Management

Major uses: Livestock grazing and homesitedevelopment in areas of the Chicote soils andseasonal use by waterfowl and shore birds inareas of the Playas

Management concerns: High content of salt andalkali, frequent flooding and ponding,compaction when wet, slow permeability, andhigh shrink-swell potential. Also, the Playasare subject to wind erosion when the surfaceis dry.

Management measures: Maintain vegetation, deferuse of heavy equipment and livestock grazingwhen the soils are wet, use special designs forhouse foundations and septic systems, and divertwater around homesites

General Soil Map Units

14 Soil Survey

2. Yeguas-Pinspring

Very deep, nearly level and gently sloping, welldrained soils that formed in alluvium from mixed rocktypes on alluvial fans and alluvial flats

Setting

Landform: Alluvial fans and flats on the bolson floor ofthe Carrizo Plain

Slope: 0 to 5 percent

Composition


Yeguas soils39 percentPinspring soils39 percentMinor soils22 percent


YeguasDepth class: Very deepDrainage class: Well drainedPosition on landform: Alluvial fans and alluvial flatsParent material: Alluvium derived from sandstone,

shale, and basaltTexture of the surface layer: LoamSlope: Nearly level and gently sloping

PinspringDepth class: Very deepDrainage class: Well drainedPosition on landform: Alluvial flatsParent material: Alluvium from mixed rock typesTexture of the surface layer: LoamSlope: Nearly level and gently sloping

Minor soils Thomhill soils on alluvial flats and alluvial fans Polonio and Wasioja soils on alluvial fans Small, weakly defined channels subject to floodingduring high-intensity rain storms Small areas of slick spots on alluvial flats

Use and Management

Major uses: Livestock grazing, dry-farmed cropland,and homesite development

Management concerns: Compaction and floodingManagement measures: Maintain vegetation, defer

livestock grazing and use of heavy equipmentwhen the soils are moist or wet, and divert wateraround homesites

Soils on Alluvial Flats, AlluvialFans, Flood Plains, and Terraces

3. Polonio-Padres-Wasioja

Very deep, nearly level to moderately sloping, welldrained soils that formed in alluvium fromsedimentary rocks on alluvial flats and alluvial fans

Setting

Landform: Alluvial flats and gently sloping andmoderately sloping alluvial fans; in the Carrizoand Elkhorn Plains


Composition


Polonio soils25 percentPadres soils19 percentWasioja soils19 percentMinor soils37 percent


PolonioDepth class: Very deepDrainage class: Well drainedPosition on landform: Alluvial fansParent material: Alluvium derived from calcareous

sedimentary rocksTexture of the surface layer: Loam, clay loam, and

gravelly loamSlope: Nearly level to moderately sloping

PadresDepth class: Very deepDrainage class: Well drainedPosition on landform: Alluvial flats and alluvial fansParent material: Alluvium derived from sedimentary

rocksTexture of the surface layer: Sandy loam and gravelly

sandy loamSlope: Nearly level to moderately sloping

WasiojaDepth class: Very deepDrainage class: Well drainedPosition on landform: Alluvial flats and alluvial fansParent material: Alluvium derived from mixed rock

typesTexture of the surface layer: Loam and sandy loamSlope: Nearly level and gently sloping


Minor soils Thomhill soils on alluvial flats and alluvial fans Capay soils on alluvial fans Yeguas and Pinspring soils on alluvial flats Gravel, sand, and borrow pits Small slick spots in nearly level areas on alluvialflats

Use and Management

Major uses: Dry-farmed cropland and livestockgrazing

Management concerns: Water erosion and, in areasof the Polonio soil, compaction

Management measures: Till on the contour, maintaina cover crop, maintain crop residue, and deferuse of heavy equipment and livestock grazingwhen the soils are wet

4. San Emigdio-Xerofluvents-Elder

Very deep, nearly level to moderately sloping, welldrained to somewhat poorly drained soils thatformed in alluvium from mixed rock types, mostlyfrom sedimentary rocks; on alluvial fans and floodplains

Setting

Landform: Alluvial fans and flood plains in the SanJuan Valley and Camatta Canyon area


Composition


San Emigdio soils29 percentElder soils22 percentXerofluvents10 percentMinor soils39 percent


San EmigdioDepth class: Very deepDrainage class: Well drainedPosition on landform: Alluvial fans and flood plainsParent material: Alluvium derived from calcareous

sedimentary rocksTexture of the surface layer: Sandy loam and loamSlope: Gently sloping and moderately sloping

XerofluventsDepth class: Very deepDrainage class: Somewhat poorly well drainedPosition on landform: Flood plains

Parent material: Alluvium derived from mixed rocktypes

Texture of the surface layer: Sand, loamy sand, andgravelly sandy loam

Slope: Nearly level

ElderDepth class: Very deepDrainage class: Well drainedPosition on landform: Alluvial fans and flood plainsParent material: Alluvium derived from mixed rock

typesTexture of the surface layer: Sandy loam and fine

sandy loamSlope: Nearly level to moderately sloping

Minor soils Sorrento soils on alluvial fans Riverwash in and along active stream channels Botella soils on alluvial fans and alluvial flats Metz soils on flood plains

Use and Management

Major uses: Dry-farmed cropland, irrigated cropland,and vineyards in areas of the San Emigdio soiland livestock grazing

Management concerns: Flooding, erosion, and, inareas of the Sorrento soil, compaction

Management measures: Maintain crop residue,maintain cover crops, and till on the contour

5. Arbuckle-Camatta

Very shallow to very deep, gently sloping to steep,well drained soils that formed in alluvium fromsedimentary rocks on stream terraces

Setting

Landform: Stream terraces in the San Juan Valley andCamatta Canyon area


Composition


Arbuckle soils65 percentCamatta soils5 percentMinor soils30 percent


ArbuckleDepth class: Very deepDrainage class: Well drained

16 Soil Survey

Position on landform: Stream terracesParent material: Alluvium derived from sandstone and

shaleTexture of the surface layer: Sandy loamSlope: Gently sloping to steep

CamattaDepth class: Very shallow and shallow to indurated

hardpanDrainage class: Well drainedPosition on landform: Stream terracesParent material: Alluvium derived from calcareous

sandstone and shaleTexture of the surface layer: LoamSlope: Moderately sloping to moderately steep

Minor soils Chanac soils on stream terraces San Emigdio, Padres, and Polonio soils on alluvialfans Xerofluvents on flood plains

Use and Management


Management concerns: Erosion, compaction in areasof the Arbuckle soil, shallow rooting depth, andslow permeability in areas of the Camatta soil

Management measures: Maintain crop residue anddefer livestock grazing and use of heavyequipment when the soils are wet

Soils on Hills and Mountains

6. Balcom-Nacimiento

Moderately deep and deep, strongly sloping to verysteep, well drained soils that formed in materialweathered from sandstone and shale on hills andmountain slopes

Setting

Landform: Hills and mountains, predominantly in thenorthwestern part of the Temblor and La PanzaRanges


Composition


Balcom soils37 percentNacimiento soils24 percentMinor soils39 percent


BalcomDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from soft,

calcareous sandstone and shaleTexture of the surface layer: LoamSlope: Strongly sloping to very steep

NacimientoDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from soft,

calcareous sandstone and shaleTexture of the surface layer: Clay loamSlope: Strongly sloping to steep

Minor soils Aido, Choice, and Calleguas soils on hills andmountains

Use and Management

Major uses: Livestock grazing and dry-farmedcropland

Management concerns: ErosionManagement measures: Maintain crop residue, till on

the contour, and do not till in the steeper areas

7. Bellyspring-San Timoteo-San Andreas

Moderately deep, strongly sloping to very steep, welldrained soils that formed in residuum weathered fromsedimentary rocks on hills and mountains

Setting

Landform: Hills and mountains in the San Juan Hillsand Temblor Range


Composition


Bellyspring soils22 percentSan Timoteo soils17 percentSan Andreas soils15 percentMinor soils46 percent


BellyspringDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountains


Parent material: Residuum weathered from sandstoneTexture of the surface layer: Sandy loamSlope: Strongly sloping to very steep

San TimoteoDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from soft,

calcareous sandstoneTexture of the surface layer: Sandy loamSlope: Moderately steep to very steep

San AndreasDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from

sandstoneTexture of the surface layer: Sandy loamSlope: Strongly sloping to very steep

Minor soils Panoza soils on hills and mountains Arnold, Akad, and Saucito on hills and mountains Rock outcrop on hills and mountains

Use and Management


Management concerns: ErosionManagement measures: Maintain plant cover and

construct trails and water troughs for livestock

8. Panoza-Beam-Hillbrick

Shallow to moderately deep, strongly sloping to verysteep, well drained soils that formed in residuumweathered from sedimentary rocks on hills andmountains

Setting

Landform: Hills and mountains in the Temblor Range,Caliente Range, Panorama Hills, Elkhorn Scarp,and Elkhorn Hills


Composition


Panoza soils25 percentBeam soils13 percentHillbrick soils11 percentMinor soils51 percent


PanozaDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from shale,

sandstone, and conglomerateTexture of the surface layer: Loam and stony loamSlope: Moderately steep to very steep

BeamDepth class: ShallowDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from soft,

calcareous shale, conglomerate, and sandstoneTexture of the surface layer: Sandy loam and fine

sandy loamSlope: Strongly sloping to very steep

HillbrickDepth class: ShallowDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from shale and

sandstoneTexture of the surface layer: Loam and sandy loamSlope: Moderately steep to very steep

Minor soils Calleguas, Jenks, Kilmer, San Timoteo, andSeaback soils and Xerorthents and XericTorriorthents; on hills and mountains Rock outcrop on hills and mountains Badlands on very steep, highly eroded hills andmountains

Use and Management

Major uses: Livestock grazingManagement concerns: Erosion and, in areas of the

Beam and Hillbrick soils, shallow rooting depthManagement measures: Maintain plant cover and


9. Aramburu-Temblor-Reward

Shallow to deep, moderately steep to very steep, welldrained soils that formed in residuum weathered fromsedimentary rocks on hills and mountains

Setting

Landform: Hills and mountains, at the higherelevations in the Temblor Range


18 Soil Survey

Composition


Aramburu soils41 percentTemblor soils19 percentReward soils10 percentMinor soils30 percent


AramburuDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from sandstone

and shaleTexture of the surface layer: Very channery clay loamSlope: Moderately steep to very steep

TemblorDepth class: ShallowDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from shale and

sandstoneTexture of the surface layer: Very channery loamSlope: Steep and very steep

RewardDepth class: DeepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from

calcareous shale and sandstoneTexture of the surface layer: Channery loamSlope: Moderately steep and steep

Minor soils Santa Lucia, Hillbrick, and Kilmer soils on hills andmountains Rock outcrop on hills and mountains

Use and Management

Major uses: Livestock grazingManagement concerns: Water erosion and, in areas

of the of Temblor soil, shallow rooting depthManagement measures: Maintain plant cover and


10. Saltos-Tajea-Gaviota

Shallow to moderately deep, moderately steep to verysteep, well drained soils that formed in residuumweathered from sandstone on hills and mountains

Setting

Landform: Hills and mountains in the San Juan Hillsand Caliente Range


Composition


Saltos soils23 percentTajea soils19 percentGaviota soils14 percentMinor soils44 percent


SaltosDepth class: Very shallowDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from sandstoneTexture of the surface layer: Loam and sandy clay

loamSlope: Moderately steep to very steep

TajeaDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from hard

sandstoneTexture of the surface layer: Loam and clay loamSlope: Moderately steep and steep

GaviotaDepth class: Very shallow and shallowDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from sandstoneTexture of the surface layer: Sandy loamSlope: Moderately steep to very steep

Minor soils Bellyspring and Millsholm soils on hills andmountains Rock outcrop on hills and mountains

Use and Management

Major uses: Livestock grazingManagement concerns: Water erosion, shallow

rooting depth in areas of the Saltos and Gaviotasoils, and wildfire

Management measures: Maintain plant cover,construct trails and water troughs for livestock,construct firebreaks, and manage brush


11. Aido-Ayar-Hillbrick

Shallow to deep, moderately steep to very steep, welldrained soils that formed in residuum weathered fromsedimentary rocks on hills and mountains

Setting

Landform: Hills and mountains, mainly in the TemblorRange


Composition


Aido soils46 percentAyar soils21 percentHillbrick soils12 percentMinor soils21 percent

Soil Properties and QualitiesAidoDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from

calcareous shale and fine-grained sandstoneTexture of the surface layer: ClaySlope: Moderately steep to very steep

AyarDepth class: DeepDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from sandstone

and shaleTexture of the surface layer: ClaySlope: Strongly sloping to steep

HillbrickDepth class: ShallowDrainage class: Well drainedPosition on landform: Hills and mountainsParent material: Residuum weathered from sandstone

and shaleTexture of the surface layer: LoamSlope: Strongly sloping to very steep

Minor soils Rock outcrop on ridgetops Xerorthents on hills and mountains

Use and Management

Major uses: Livestock grazing and dry-farmedcropland

Management concerns: Erosion, a high shrink-swellpotential and compaction in areas of the Aido and

Ayar soils, and shallow rooting depth in areas ofthe Hillbrick soil

Management measures: Maintain crop residue or plantcover, till on the contour, avoid tilling in the steeperareas, and defer grazing and use of heavyequipment when the soils are wet

12. Godde-Xerorthents-Rock Outcrop

Rock outcrop and shallow, steep and very steep, welldrained and somewhat excessively drained soils thatformed in material derived from sandstone at higherelevations on mountains

Setting

Landform: High mountains in the Caliente RangeSlope: 30 to 75 percent

Composition


Godde soils40 percentXerorthents20 percentRock outcrop15 percentMinor soils25 percent


GoddeDepth class: ShallowDrainage class: Somewhat excessively drainedPosition on landform: MountainsParent material: Residuum weathered from sandstoneTexture of the surface layer: Sandy loamSlope: Steep and very steep

XerorthentsDepth class: Very shallow and shallowDrainage class: Well drainedPosition on landform: MountainsParent material: Residuum weathered from

sandstoneTexture of the surface layer: Sandy loamSlope: Steep and very steep

Rock outcrop Exposures of hard sandstone and shale

Minor soils Gaviota, Saltos, Panoza, Aido, Nacimiento, andBeam soils on the lower, warmer mountain slopes Yeguas soils on alluvial fans in high mountain areas

Use and Management

Major uses: Livestock grazingManagement concerns: Water erosion and shallow

rooting depth

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Management measures: Maintain plant cover andconstruct trails and water troughs for livestock

13. Semper-Rock Outcrop-Muranch

Rock outcrop and shallow to moderately deep, steepand very steep, well drained soils that formed inresiduum weathered from basalt and sandstone onhills and mountains

Setting

Landform: Mountains in the Caliente RangeSlope: 30 to 100 percent

Composition


Semper soils35 percentRock outcrop11 percentMuranch soils8 percentMinor soils46 percent


SemperDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Mountains in the Caliente

RangeParent material: Residuum weathered from soft

sandstoneTexture of the surface layer: Very fine sandy loamSlope: Steep and very steep

Rock outcrop Exposures of basalt, sandstone, or shale on hillsand mountains

MuranchDepth class: Moderately deepDrainage class: Well drainedPosition on landform: Mountains in the Caliente

RangeParent material: Residuum weathered from basaltTexture of the surface layer: LoamSlope: Steep and very steep

Minor soils Xerorthents on hills and mountains

Badlands on very steep, highly eroded hills andmountains Lithic Torriorthents, Hillbrick soils, and Kilmer soilson hills and mountains

Use and Management

Major uses: Livestock grazingManagement concerns: Water erosionManagement measures: Maintain plant cover and


14. Cieneba-Rock Outcrop

Rock outcrop and shallow, steep and very steep,somewhat excessively drained soils that formed inresiduum weathered from granitic rock on hills

Setting

Landform: Hills in the La Panza RangeSlope: 30 to 75 percent

Composition


Cieneba soils75 percentRock outcrop5 percentMinor soils20 percent


CienebaDepth class: Very shallow and shallowDrainage class: Somewhat excessively drainedPosition on landform: Hills of the La Panza RangeParent material: Residuum weathered from graniteTexture of the surface layer: Coarse sandy loamSlope: Steep and very steep

Rock outcrop Exposures of granitic rock on hills and mountains

Minor soils Gaviota and Arnold soils on hills and mountains Badlands on hills

Use and Management

Major uses: Wildlife habitat and watershedManagement concerns: Water erosion and wildfireManagement measures: Maintain plant cover,

construct firebreaks, and manage brush

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Figure 9.An aerial view of Camatta Canyon from the north showing the geomorphic setting of soils. Elder sandy loam and SanEmigdio sandy loam support carrots and alfalfa on the irrigated flood plain. Arbuckle sandy loam supports vineyards on thestream terraces adjacent to the flood plain. Balcom loam and Nacimiento clay loam support rangeland on the hills to theeast of the canyon. Camatta loam supports rangeland on the up-lifted stream terraces sloping to the west of the canyon.

Detailed Soil Map Units

The map units delineated on the detailed soil mapsin this survey represent the soils or miscellaneousareas in the survey area. The soils or miscellaneousareas are components of the map units. The map unitdescriptions in this section, along with the maps, canbe used to determine the suitability and potential of aunit for specific uses (fig. 9). They also can be used toplan the management needed for those uses. Moreinformation about each map unit is given under theheading Use and management of Soils.

A map unit delineation on a soil map represents anarea dominated by one or more major components. Amap unit is identified and named according to thetaxonomic classification of the major component.Within a taxonomic class there are precisely definedlimits for the properties of the soils. On the landscape,however, the soils are natural phenomena, and theyhave the characteristic variability of all naturalphenomena. Thus, the range of some observedproperties may extend beyond the limits defined for a

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taxonomic class. Areas of soils of a single taxonomicclass rarely, if ever, can be mapped without includingareas of other taxonomic classes. Consequently,every map unit is made up of components for which itis named and some minor components that belong totaxonomic classes other than those of the majorcomponents.

Most minor soils have properties similar to those ofthe dominant soil or soils in the map unit, and thusthey do not affect use and management. These arecalled noncontrasting, or similar, components. Theymay or may not be mentioned in a particular map unitdescription. Other minor components, however, haveproperties and behavioral characteristics divergentenough to affect use or to require differentmanagement. These are called contrasting, ordissimilar, components. They generally are in smallareas and could not be mapped separately becauseof the scale used. Some small areas of stronglycontrasting soils or miscellaneous areas are identifiedby a special symbol on the maps. The contrastingcomponents are mentioned in the map unitdescriptions. A few areas of minor components maynot have been observed, and consequently they arenot mentioned in the descriptions, especially wherethe pattern was so complex that it was impractical tomake enough observations to identify all the soils andmiscellaneous areas on the landscape.

The presence of minor components in a map unitin no way diminishes the usefulness or accuracy ofthe data. The objective of mapping is not to delineatepure taxonomic classes but rather to separate thelandscape into landforms or landform segments thathave similar use and management requirements. Thedelineation of such segments on the map providessufficient information for the development of resourcepla

Soil Survey of San Luis Obispo County, California, Carrizo Plain Area

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