UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA The Classification and Evaluation of the Soils of Western San Diego County R. EARL STORIE BULLETIN 552 JUNE, 1933 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA CONTENTS PAGE Introduction 3 Physiography and topography 6 Soils: grouping and descriptions 7 Evaluation of the soils 31 Summary 36 Acknowledgments 37 Glossary of soil terms 38 The Classification and Evaluation of the Soils of Western San Diego County 1 E. EARL STORIED INTRODUCTION During 1929 and 1930 detailed soil surveys covering the western half of San Diego County were made and are now being prepared for publi- cation in three reports under the names of the Oceanside, Capistrano, and El Cajon areas. 3 These areas are shown on the sketch map (fig. 1). The Capistrano Area covers those portions of Orange and San Diego counties lying south of Township 6 South and west of the Riverside County line, while the south boundary coincides with the south boundary of the Santa Margarita Rancho. The Oceanside Area lies to the south and covers the territory from the coast east into the mountains beyond Pala, Pasqual, and Poway valleys, and south to the north line of Town- ship 15. The El Cajon Area extends south to the international boundary and east well into the mountains beyond Lyons Valley. Together these surveys cover all the western half of San Diego County and include most of the agricultural lands. A reconnoissance soil survey 4 covering most of San Diego County was made during the winter of 1915 as one of six such surveys that covered the major portions of southern California, the Sacramento and San Joaquin valleys, and the San Francisco Bay Region. These were gen- eralized surveys with maps made on the scale of 2 miles to the inch (the scale of the Sacramento Valley map is 4 miles to the inch) showing the 1 Received for publication September 13, 1932. 2 Assistant Soil Technologist in the Experiment Station. s Cooperative work between the Division of Soil Technology of the University of California and the United States Department of Agriculture Bureau of Chem- istry and Soils: Storie, R. Earl, and E. J. Carpenter. Soil Survey of the Oceanside Area, Cali- fornia. (In press.) Carpenter, E. J., and R. Earl Storie. Soil Survey of the Capistrano Area, Cali- fornia. (In preparation.) Storie, R. Earl, and E. J. Carpenter. Soil Survey of the El Cajon Area, Cali- fornia. (In preparation.) 4 Holmes, L. C, and R. L. Pendleton. Reconnoissance soil survey of the San Diego Region, California. U. S. Dept. Agr. Bur. Soils, Field Operations 1915, Re- port 64:2509-2581. 1919. 4 University of California — Experiment Station soils in rather inclusive groupings of types within a series, or even in some cases of undifferentiated series. Individual soil types were shown wherever of sufficient extent to be accurately separated out and shown Loguna beacH^'n .: • -^.. f LLy ER5IDE COUNTY ./pSAN DI^GO COUNTY Fail'brook Fig. 1. — Sketch map of the western portion of San Diego County and south- western Orange County, showing location of various soil groups, and the area covered in each of the detailed areas (Capistrano, Oceanside, and El Cajon). B, Mountainous, stony, or broken land (includes isolated areas of group I soils). I, Soils of group I. Ic, Heavy -textured soils of subgroups 15 and Ic occurring on the coastal plain and derived from calcareous parent material. II, Soils of group II, with inclusions of group III soils. III, Light-textured soils from marine -terrace materials (Elkhorn and Marina series). IV, Semimaturely and maturely weathered coastal plain soils of group IV. on the map, but in most cases related types were combined in the recon- noissance surveys. These reconnoissance surveys have served as a guide to the general soil conditions in the several regions, but are being sup- Bul. 552] Soils of Western San Diego County 5 planted as rapidly as facilities permit by detailed soil surveys made on the much larger scale of 1 mile to the inch on the map. These detailed surveys show occurrences of soils in areas as small as 10 acres or less, while the reconnoissance surveys rarely show bodies of soil of less area than 160 acres. The detailed maps are much more complete and show practically all of the different bodies of soils that are of sufficient size to place on the base maps used in the field work. During the fifteen years that elapsed between the making of the Recon- noissance Survey of the San Diego Region and the recently completed detailed surveys, much progress has been made in soil science and in the recognition and interpretation of soil characteristics in the field and laboratory. By reason of recent progress in the basic sciences, particu- larly chemistry and physics, there are now available means of measur- ing soil differences that formerly could only be approximated. This has made possible a better understanding of soil morphology 5 and a mate- rial advance in soil classification. During the field work the soils were studied in place, in their natural condition, and the details of the soil profile and their several horizons carefully noted (fig. 4). After these extensive studies in the field, areas representative of selected soil types were located, samples were taken from each horizon of the profile and subjected to physical and chemical study in the laboratories to supple- ment the data gathered in the field. As a result of these studies the new surveys are not only more detailed in the mapping but also are much more complete and definite in the soil descriptions. New series of soils not recognized in the broader classifica- tion of the Reconnoissance Survey have been discovered, studied, de- scribed, and named ; better correlation between the soils of these areas and other parts of the state has caused many changes in series names (table 1) and old series have been more specifically defined. This paper sets forth the salient relationships and differences of the soils of San Diego County and the changes that have been made from the classifica- tion in the Reconnoissance Survey. No attempt is made to give full de- tails of individual soil descriptions ; these will appear in the surveys of the Oceanside, Capistrano, and El Cajon areas. An evaluation or comparative rating of the soils in the three detailed surveys is included in this paper. This is a rating on a percentage basis of all the soil types, soil phases, and miscellaneous materials as mapped in the surveys. Using this rating, or index, the soils are divided into six grades and their distribution shown on maps of the three areas. 5 This and other technical terms are denned in the "Glossary of Soil Terms, page 38. University of California — Experiment Station PHYSIOGRAPHY AND TOPOGRAPHY The portion of San Diego County covered by these surveys consists of two broad physiographic divisions : a coastal plain from 1 to 18 miles in width composed of flat-topped marine terraces, in places badly cut by erosion ; and a mountainous highland district of crystalline rocks that _j LU HIGHLAND AND M0UNTAIN0U5 AREA o v 2 4 6 6 10 12 \- DISTANCE IN MILES FROM COAST EAST NEAR CARLSBAD § ALONG LINE AB [U Fig. 2 2 o UJ -Cross section showing elevation and major soils along line AB (fig. 1) through Carlsbad. Major physiographic divisions also shown. COASTAL PLAIN 1 EL 1 CAJON VALLEYI MOUNTAINOUS 3 C .1 ASEA 1600 1200 600 400 5 o =2 a. jq 1 _ \h i , /] \ 1 1 1 2 4 6 6 10 12 14 16 18 DISTANCE IN MILES EAST FROM MISSION BAY ALONG LINE CD 20 22 24 Fig. 3 — Cross section showing elevation and major soils along line CD (fig. 1) through Mission Bay and El Cajon Valley. covers all the remainder or the eastern portion of the area (figs. 2 and 3 ) . The boundary between the coastal plain and the highland district coincides with that between soil groups IV and I as shown on the sketch map (fig. 1). The coastal plain is dissected by stream channels, many of them heading in the eastern portion and draining the mountainous area. Bul. 552] Soils of Western San Diego County 7 The Santa Margarita, San Lnis Rey, San Dieguito, San Diego, Sweet- water, and Tia Juana rivers all have fairly large drainage areas and also have accumulated the extensive alluvial deposits along their lower courses which form the recent soils of group II. A number of box-like valleys occur at or near the break between the coastal plain and the mountains. These are filled with alluvial deposits of different ages that give rise to maturely weathered, moderately weathered, and unweathered soils of groups IV, III, and II. The Escon- dido, Poway, and El Cajon valleys are the largest and most typical of these filled valleys. Geologically, the coastal plain is made up of tertiary deposits of clay beds, shales, sandstones, conglomerates, limestones, and other slightly to moderately consolidated material ; while the mountainous district is of igneous rock material mainly granitic in character (fig. 6) . Sandy beach deposits occupy some of the terraces immediately bordering the coast. The coastal plain rises from sea level to an elevation of 200 to 600 feet. The maximum elevation of the upland region exclusive of a few high peaks is about 2,700 feet above sea level in the vicinity of Alpine. SOILS: GROUPING AND DESCRIPTIONS Climatic factors such as precipitation, temperature, humidity, etc., have a marked effect on the soils of any region. The western part of San Diego County receives from 8 to 20 inches of rain, most of which falls during the winter months. The lowest amount is received along the coast and increases eastward. Winters are warm with little frost on the coastal plain, while the summer heat is considerably tempered by cool breezes from the ocean and occcasional high fogs which intercept the sun's energy and reduce the heat and evaporation. Under these conditions vegetation grows freely during winter when the soils are covered with grass and herbage, but by midsummer these have dried up and the soil is dry and often bare. Under these climatic influences the rainfall does not penetrate deeply into the soil, most of it being used by the growing vegetation during the rainy season. The soils usually are leached only through the surface horizons, are low in organic matter, and prevail- ingly grayish brown, although there is a rather wide range in color. Differences in parent material, degree of weathering, method of for- mation, and lime content have all contributed their share to the diversity of soils encountered. The soils of the highland area generally occur on rolling to mountainous topography where the composition of the parent material has considerable influence on the character of the resulting soils. These soils usually exhibit a youthful or only slightly weathered 8 University of California — Experiment Station profile. Coarse crystalline rocks such as granite give sandy loam soil, while the denser rocks produce finer-textured heavier soils. Bedrock is usually encountered at a shallow depth under such conditions. The soils of the stream valleys consist of outwash from the upland re- gion ; they exhibit young or immature profiles and have a wide range in color and in lime and alkali content. The coastal plain soils have light to medium-textured surface horizons and heavy clay subsoils. Of these the Olivenhain, Tierra, and Las Flores series have a typical solonetz subsoil (horizon B), with the columnar structure and alkaline reaction in this horizon, while the Redding series have heavy-textured subsoils of distinctly acid reaction without the solonetz structure. In any system of soil classification a broader or more comprehensive idea can be had of the soils of a district if they can be grouped together on the basis of common characteristics, especially when these are cor- related with common agricultural values. In the San Diego Reconnois- sance Survey the soils are placed in three broad groups defined as (1) residual soils derived through the disintegration or weathering in place of consolidated rocks, (2) soils derived through the weathering and modification of old unconsolidated waterlaid deposits, and (3) recent alluvial soils. 6 In the detailed surveys of the Capistrano, Oceanside, and El Cajon areas, this scheme has been further elaborated to include four main groups of soils, namely : group I, primary or residual soils derived through the weathering in place of consolidated rocks with the develop- ment of soils having young or immature profiles and which usually have the bedrock or parent material occurring less than 6 feet from the sur- face ; group II, unweathered secondary soils from alluvial material oc- curring in river valleys and on alluvial fans, without definite horizon development and more than 6 feet in depth ; group III, slightly to mod- erately weathered secondary soils from alluvial or coastal plain mate- rials having permeable subsoils and substratum to depths of 6 or more feet ; group IV, weathered secondary soils from old alluvial or coastal plain materials having dense or relatively impermeable heavy clay sub- soils or hardpan horizons formed as the natural result of soil weather- ing processes. The four groups of soils listed below are separated on the basis of maturity of profile and mode of formation. The soil series in each of these groups have been further subdivided into subgroups on the basis of reaction of the soil mass (table 1) . In this table soil series are shown 6 Holmes, L. C, and E. L. Pendleton. Eeconnoissance soil survey of the San Diego Eegion. Field Operations of the Bureau of Soils, 1915. 77 p. Bul. 552] Soils of Western San Diego County in subgroups having common reaction characteristics and surface soil colors, as well as profiles of comparable age and a common mode of for- mation. It will be noted that soil series in a subgroup have similar agri- cultural values. GROUP I, PRIMARY SOILS Group I consists of primary soils with youthful to immature profiles, formed in place by the weathering of parent bedrock or substratum. They occur on rolling to mountainous topography east of the coastal plain. Subgroup a, Noncalcareous Soils and Subsoils. — Fallbrook series Las Posas series Vista series Carlsbad series Konokti series Ysidora series • Escondido series TABLE 1 Classification of Soils of Western San Diego County and Southern Orange County Subgroup (reaction of soil profile) Composition of parent material Color of surface Series Type As shown in detailed surveys Series names as shown in reconnoissance of 1915 Group I, Primary Soils [sandy loam 1 granitic light brownish red or reddish Fallbrook J fine sandy loam I fine sandy loam, 1 Sierra brown [ stony phase [ sandy loam 1 granitic brown or grayish brown Vista i sandy loam, stony ( phase very fine sandy loam ^Holland a very fine sandy mixed, yellowish brown Escondido loam , stony ■ Sierra Non- schists phase calcareous stony very fine soils sandy loam and subsoils mixed basic igneous brown Konokti /stony loam \gravelly loam f fine sandy loam lOlympic 1 mixed basic brownish red Las Posas \ stony fine sandy fAiken igneous { loam gravelly sandy loam J mixed brown Ysidora i gravelly sandy •Olympic sedimentary loam, dark-col- ored phase [loamy fine sand I sandstone brown Carlsbad i loamy fine sand, [ gravelly phase fSan Joaquin 10 University of California — Experiment Station Table 1 — (Continued) Subgroup (reaction of soil profile) Composition of parent material Color of surface soil Series Type As shown in detailed surveys Series names as shown in reconnoissance of 1915 Group I, Primary Soils (Continued) Non- calcareous surface, calcareous subsoil and bedrock Calcareous soils and subsoils calcareous- sedimentary calcareous- sedimentary calcareous- sedimentary calcareous- sedimentary light brown dark gray brown dark brownish gray Altamont Diablo Ayar Linne fine sandy loam clay loam I clay loam, gravel- ly phase [clay [ clay adobe | clay adobe, steep phase clay adobe, brown phase j clay loam \clay [loam J sandy clay loam Jclay [stony clay Diablo or Montezuma G roup II, Unweathered Secondary Soils [sandy loam I granitic light brown Hanford 1 sandy loam, [Hanford a j gravelly phase [fine sandy loam J Non- calcareous* granitic light gray or light Tujunga fine sand Tujunga soils and brownish gray subsoils [loamy sand I mixed light brownish Laguna SJ X O oo — o E <- w> o in. i |||| o to o ^^^^^^^^5 41 ^ H n £ g .> r Sa; o H v_ a O O— CD 2 § § 2 " <\2 ^ — C\i vD °0 O c\2 IO ^ VO N S3H0NI NI Hld3Q C3HDNI NI Hld3Q 28 University of California — Experiment Station Subgroup c, Noncalcareous Surface Soils, Calcareous Subsoils ( Solo- net z Soils). — AJiso series Huerhuero series Stockpen series Merriam series Montezuma series The general sequence and number of the structural, consistence, tex- tural, and reaction horizons in these soil series are similar. All occur on terrace or sloping-bench surfaces, and are fairly mature as evidenced Fig. 15. — Erosion in Las Flores soils, group IV, 4 miles east of Oceanside. The heavy clay subsoil has a fluted appearance. These soils have infertile surface soils and very heavy intractable clay subsoils. by the accumulation of colloidal clay in the subsoils and the nodular ac- cumulation of lime in the lower subsoils. They differ from the Oliven- hain, Las Flores, Tierra group described previously in the presence of the horizon of lime accumulation that breaks into cube-like fragments, and in the less consolidated nature of the parent material. All except the heavy-textured Montezuma soils have the sharp line of demarcation be- tween the surface soil and subsoil, with the columnar solonetz-like char- acteristics of this horizon. The Aliso soils are reddish brown, the Huerhuero light brownish gray or light grayish brown, and the Stockpen light gray. These all are de- rived from mixed material. Merriam soils are of light reddish-brown color and derived largely from granitic material. They are associated with the Ramona and other Bul. 552] Soils of Western San Diego County 29 similar soils derived from granitic material and represent a fairly ma- ture soil development of this kind of material under low rainfall. A typical profile of a Huerhuero fine sandy loam is as follows. Aliso, Stockpen, and Merriam soils have similar characteristics (figs. 4 and 16). &**- '^Btfc 1 * am ■ Btefc A ^^ •• H '. ■;' <■■'.■'■'* Fig. 16. — Huerhuero fine sandy loam, group IV, Capistrano area. Note the sharp line of contact between surface and subsoil horizons. An accumulation of lime at a depth of about 3 feet is indicated by the arrow. The Ai horizon consists of 4 to 10 inches of slightly acid (pH 6.0 to 6.6) friable sandy loam or fine sandy loam ; A 2 horizon of light gray laminated sandy loam y 1Q to y^ inch in thickness occurring as a thin coating over the clay horizon ; B x horizon 8 to 14 inches in thickness of extremely compact columnar clay, distinctly basic in reaction (pH 7.1 to 8.5), and high in colloidal clay; B 2 horizon of compact clay loam or clay, breaking up in regular-shaped cubes with lime present as nodules and in seams and cracks; and the parent material or C horizon of a moderately compact loam or sandy loam having a pH of 7.0 to 8.0, but having practically no soluble salts present. The detailed studies show the typical Montezuma soils to be of minor extent. Most of the soils that were mapped as Montezuma in the Recon- noissance Survey have been classified as the Diablo or Linne series on the basis of profile differences and the consolidated calcareous parent mate- rial. The Montezuma soils consist of heavy-textured (clay adobe) non- calcareous dark gray surface soils and heavy-textured lighter-colored 30 University of California — Experiment Station calcareous clay subsoils, with a lower subsoil having a cubical structure and containing nodular accumulations of lime. They are derived from heavy-textured sediments and are underlain by a substratum of dull- brownish-gray, irregularly calcareous, dense but unconsolidated, clayey deposits. The soils included in this group have a somewhat higher value than those of the preceding group (Olivenhain, Las Flores, and Tierra series) since they have deeper surface soils and more permeable structure of the lower subsoil, and do not have the degree of consolidation of the parent material, and the salinity so often present in the other group. The heavy relatively impervious solonetz upper subsoil horizon limits the penetration of moisture, roots, and air, making the production of deep-rooted irrigated crops very difficult. The Merriam was included with the Placentia of the Reconnoissance Survey. It is similar to the Placentia in most soil characteristics, but differs from it in having the solonetz-like B x horizon and accumulated lime in the B 2 horizon. The Aliso and Huerhuero series were included with the Kimball and Las Flores of the Reconnoissance Survey. They differ mainly in the ac- cumulated lime. The Aliso is a new soil series recognized for the first time in San Diego County, while the Huerhuero was established in the Paso Robles area to include the lighter-colored more arid equivalent of the Antioch series. The Stockpen soils were included with the Las Flores of the Recon- noissance Survey from which they differ mainly in their lighter color and in the presence of accumulated lime. Subgroup d, Noncalcareous Surface Soils, Calcareous Subsoils, with Hardpan or Hardpan-like Substratum. — Monserate series The Monserate series is characterized by the presence of a light brown- ish-colored iron-and-silica-cemented hardpan that may be calcareous in the upper portion in seams and crevices. A cubical-structured calcare- ous clay layer overlies the hardpan. The A, B 1? and B 2 horizons are similar in color to those of the Aliso and Merriam series in being brown or reddish brown. The hardpan often rests on a brown, moderately con- solidated substratum of similar color so that it is often difficult to deter- mine the thickness of the hardpan. The hardpan or hardpan-like sub- stratum usually occurs at a depth of 3 to 4 feet from the surface. Mon- serate soils are of mixed origin, although granitic material often shows up fairly distinctly in the profile. In the Reconnoissance Survey they were included as a hardpan variation of the Placentia. Bul. 552] Soils of Western San Diego County 31 EVALUATION OF THE SOILS In table 2, all the soil types of the El Cajon, Oceanside, and Capistrano areas have been arranged in a comparative rating on the basis of the degree to which they present conditions considered favorable for the growth of plants. Soils presenting the most favorable general conditions Fig. 17. — Grouping of soils of El Cajon Area, San Diego County, California, on the basis of soil index. Grade 1 — Excellent soils, index 80-100. 2— Good soils, index 60-80. 3 — Fair soils, index 40-60. 4 — Poor soils, index 20-40. 5 — Very poor soils, index less than 20. 6 — Miscellaneous nonagricultural materials, index 0-5. are given a rating of 100 per cent, and the other soils are rated in com- parison. This soil rating, or index of soil valne, 7 is based on the soil factor alone and does not include the effect of local climate, availability of water for irrigation, the location, or other site factors that enter into land appraisals. In arriving at the "index" or rating on the individual 7 Storie, K. Earl. An index for rating the agricultural value of soils. 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