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

HIGHLAND AND M0UNTAIN0U5
AREA

o v 2 4 6 6 10 12

\- DISTANCE IN MILES FROM COAST EAST NEAR CARLSBAD
§ ALONG LINE AB

Fig.

2 o

-Cross section showing elevation and major soils along line AB (fig. 1)
through Carlsbad. Major physiographic divisions also shown.

COASTAL PLAIN

1 EL

CAJON

VALLEYI

MOUNTAINOUS

ASEA

1600
1200
600
400

5 o

_<u

j|l_

■o

1 1

<JT3

„ C
O

1 o

\ o "l

Olive

■^

i ,

2 4 6 6 10 12 14 16 18

DISTANCE IN MILES EAST FROM MISSION BAY
ALONG LINE CD

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

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

granitic

light brownish
red or reddish

Fallbrook

J fine sandy loam
I fine sandy loam,

1 Sierra

brown

[ stony phase
[ sandy loam

granitic

brown or grayish
brown

Vista

i sandy loam, stony
( phase

very fine sandy
loam

^Holland

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

mixed basic

brownish red

Las Posas

\ stony fine sandy

fAiken

igneous

{ loam

gravelly sandy
loam

mixed

brown

Ysidora

i gravelly sandy

•Olympic

sedimentary

loam, dark-col-
ored phase

[loamy fine sand

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

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

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

roup II, Unweathered Secondary

Soils

[sandy loam

granitic

light brown

Hanford

1 sandy loam,

[Hanford

j gravelly phase
[fine sandy loam

Non-

calcareous*

granitic

light gray or light

Tujunga

fine sand

Tujunga

soils and

brownish gray

subsoils

[loamy sand

mixed

light brownish

Laguna

<j loamy fine sand

[Yolo

sedimentary

gray

[sandy loam
[sand

granitic

light gray

Cajon

i fine sand

[fine sandy loam

fine sandy loam

\ Hanford

very fine sandy

granitic

dark brownish

Foster

loam

(Foster

Calcareous

gray

very fine sandy

soils and 1

loam, gray

subsoils

mixed cal-

phase

careous sedi-

dark gray

Agueda

clay loam

Dublin

mentary

floam

)

mixed

dull brownish
gray

Alviso

■j very fine sandy
[ loam

[Tidal Marsh

Bul. 552] Soils of Western San Diego County

Table 1 — (Continued)

Subgroup
(reaction of

Composition

parent

material

Color of surface
soil

Series

Type

Series names
as shown in

soil
profile)

As shown in detailed surveys

reconnoissance
of 1915

Group III, Slightly to Moderately Weathered Secondary Soils

sandy coastal

brown

Marina

/loamy sand

\ Kimball

Non-

plain

\ loamy fine sand

calcareous

profile,

slightly to

moderately

sandy coastal

brown

Elkhorn

loamy sand

Kimball

acid sur-

plain

face soils

f sandy loam

granitic

brown

Greenfield

1 sandy loam, cal-
| careous subsoil
[ phase

1 Ramona or
[Hanford

[ sandy loam

\ Ramona

granitic

brown

Ramona

-j sandy loam, stony
[ phase

Non-

calcareous

soils and

(sandy loam

^Kimball

subsoils

mixed

brown

Hames

i sandy loam, fria-
{ ble subsoil phase

[loamy sand

| fine sandy loam

largely

dull brownish

Botella

" sandy clay loam

[►Dublin

sedimentary

gray

sandy clay loam,

brown phase

granitic

dark brownish

San Marcos

/fine sandy loam
\ loamy fine sand

) Foster

gray

largely

light brown

Sorrento

clay loam

Yolo

sedimentary

largely basic

dark brown

Farwell

gravelly sandy

Yolo

igneous

loam

calcareous

dull gray

Commatti

sandy loam

Yolo or Dublin

Non-

sedimentary

calcareous-

surface

sandy loam

soils,

fine sandy loam

calcareous

fine sandy loam,

subsoils

mixed

dull brownish
gray

Salinas

light-colored

phase
loam
clay loam

Yolo

mixed

dark gray

Clear Lake

/loam

^Dublin

\ sandy clay loam

12 University of California — Experiment Station

Table 1 — (Concluded)

Subgroup

Composition

Series

Type

Series names

(reaction of

of
parent

Color of surface
soil

as shown in

soil

reconnoissance

profile)

material

As shown in

detailed surveys

of 1915

Group IV

, Semimaturely or

Maturely Weathered Soils

a
Acid soils

(gravelly sandy

1 Redding or

and

mixed

reddish brown

Redding

1 loam

1 rough broken

subsoils—

J stony sandy loam

[ land

with

[sandy loam

hardpans

[loamy fine sand

mixed marine

light brown

Olivenhain

■j gravelly sandy

Non-

terrace

[ loam

Las Flores

calcareous

soils and

[fine sandy loam

Las Flores

subsoils •

mixed marine

light gray

Las Flores

1 fine sandy loam,

and

resting on

terrace

| friable subsoil

Kimball

a consoli-

{ phase

undifferen-

dated

tiated

sub-

mixed marine

dull brownish

Tierra

(sandy loam

stratum

terrace

gray

\loam

1 sandy loam

J
)

granitic

light reddish
brown

Merriam

1 fine sandy loam
| fine sandy loam,
{ clay phase

[sandy loam

[Placentia

mixed

reddish brown

Aliso

I fine sandy loam

I Kimball

] fine sandy loam,
[ heavy phase

Non-

calcareousl
surface

light brownish

f Las Flores

mixed

gray or light

Huerhuero

fine sandy loam

I and Kimball,

soils,

grayish brown

| undifferen-

calcareous

[ tiated

subsoils

f fine sandy loam

}

mixed

light gray

Stockpen

1 fine sandy loam,
j heavy-textured
[ phase

I Las Flores

mainly

dark gray

Montezuma

clay adobe

Montezuma

d
Non-

sedimentary

calcareous

surface

mixed

brown

Monserate

sandy loam

Placentia

soils,

calcareous

subsoils,

hardpan-

like sub-

stratum

Bul. 552]

Soils op Western San Diego County

SOIL
TYPE

PROFILE

COLOfc

TEXTURE STRUCTURE

CONSISTENCE
AND DENSITY

Vista

sandy loam
Group I a

light
grayiah brown

sandy
loam

granular

friable

brown

gritty
loam

medium
cloddy

moderately
compact

granitic bedrock

Han ford
sandy loam

Group Ha

72 m;

light
brown

sandy
loam

friable

light
brown

variable -
textured

structureless

friable

Uamona
sandy loam

Group Ulb

A 5

5 ,4

?*«

-xHi

50
C.

: -. '

sandy loam

granular

friable

reddish
brown

sandy loam
loam

medium granular
nut structure

shcjhtly £ompact_

moderately
compact

dull reddish
brown

sandy
clay loan

fairly compact
dense, hard

brown

loam

amorphous

slightly
compact

Merriam
sandy loam

Group Wc

brown

sandy loam

granular

friable

dull brownish
red

columnar
(.solonetz)

very compact
dense and hard

:lay or clay
loam

compact and
hard

light brown

varible
textured

cloddy

fairly compact
and hard

Fig. 4. — Soil profiles shown diagrammatically with one soil from each major
group. All four soils are derived from acid igneous (granitic) material.

Soils in this subgroup have surface soils of brown or reddish-brown
color with brown, reddish-brown, red, or yellowish subsoils. Bedrock
usually occurs at a depth of from 1 to 4 feet from the surface. Stones are
often present in shallow areas or on steep slopes. A moderate degree of
leaching and of downward migration of clay is indicated by a small but
definite accumulation of colloidal clay in the subsoils. The moisture-
holding capacity of the surface soils is low to medium, and the subsoils
slightly higher. Both surface soils and subsoils give reactions of pH 6.6
to 7.2. In other parts of the state where the rainfall is much heavier (30

14 University of California — Experiment Station

to 60 inches) soils from the same kind of parent material are distinctly
acid in reaction (pH 5.7 to 6.3).

The Fallbrook and Vista series of soils are formed by the weathering
in place of granitic rocks. The Fallbrook is light red to reddish brown
with a redder, denser, and heavier-textured subsoil, while the Vista is
brown or light brown throughout the profile (fig. 4) with less evidence
of clay accumulation in the subsoil. In the Reconnoissance Survey they
were included with the Sierra and Holland series, respectively, which
they resemble in many respects, differing particularly by being more
basic in reaction. The Sierra and Holland soils are formed where the
rainfall is much heavier and the effects of leaching much more evident,
while the Fallbrook and Vista are their equivalents formed under more
arid conditions. The Fallbrook and Vista soils are all of light (sandy)
texture. Coarse sandy loam, stony sandy loam, and fine sandy loam
types occupy a large acreage over the highland (fig. 5) area, inter-
spersed with rough mountainous and rough stony land (fig. 6), and,
where sufficient water is available for irrigation purposes and where
the topography is favorable, are considered desirable for a wide range
of crops.

The Escondido soils are yellowish brown to reddish brown with very
friable subsoils resting directly on the disintegrating schistose parent
bedrock. They were included with the Sierra soils in the Reconnoissance
Survey, from which they differ in profile characteristics and in origin.
The soils are of very fine sandy loam or silt loam texture and are of good
agricultural value where the stone content is not too high and the soils of
good depth over the bedrock.

The Konokti and Las Posas series are derived from basic igneous rocks
(diorites, diabases, etc.) and occur along the boundary between the
coastal plain and the upland regions. In the Reconnoissance Survey the
brown-colored Konokti was included with the Olympic and the brownish-
red Las Posas with the Aiken series. They resemble the Olympic and
Aiken series but, since they were formed under more arid conditions, are
more basic in reaction. Limiting factors for agricultural use are the
steepness of slopes, stone content, and relatively shallow depth in cer-
tain areas.

The Carlsbad series in the Reconnoissance Survey was included in the
San Joaquin series, but the more detailed studies showed that instead
of being a hardpan, the red sandstone-like material beneath the soils is a
substratum of parent material from which they are being weathered
(fig. 7) . They occupy elevated ridges paralleling the coast. The soils are
brown, sandy, and contain large quantities of small rounded concretions

Bul. 552]

Soils of Western San Diego County

("iron pellets"). Subsoils are similar to the surface soils, without any
clay accumulation, and rest on the standstone-like substratum at depths
of 2 to 5 feet. The organic content and general fertility of the Carlsbad

Fig. 5. — Area of Vista and Fallbrook soils, east of El Cajon. Note rough stony
areas in distance and rock outcrops in foreground.

Fig. 6. — Rough mountainous area east of coastal plain shown as B on the
sketch map (fig. 1). Note small area of tillable land.

series of soils is low, but good results are being secured with bulbs, truck
crops, etc., where the soil is heavily fertilized, since the sandy texture
makes it easy to handle.

The Ysidora soils are brown and rest on a grayish-brown hardpan-like
parent material at depths of 1 to 3 feet. Subsoils are variable, consisting
of brown, fairly compact material that may range in texture from a

16 University of California — Experiment Station

sandy loam to a clay. The series occurs on sloping terrace-like topog-
raphy, having small mounds and depressions referred to as "hogwal-
lows" scattered over the surface. The surface soils are of gravelly sandy
loam texture. Soils of this series are of low agricultural value on account
of their variable depths and uneven surface. The Ysidora was included
with the Olympic series in the Reconnoissance Survey.

Fig. 7. — Profile of Carlsbad loamy fine sand, east of Ocean-
side, included in group I. Note the hardpan-
like substratum.

Subgroup b, Noncalcareous Surface Soils, Calcareous Subsoils, and
Calcareous Parent Materials. —
Altamont series
Diablo series

The Altamont and Diablo series are derived from calcareous sedi-
mentary rocks and occur on the coastal plain. The Altamont soils are
light brown or brown, while the Diablo is dark gray. Subsoils are of
somewhat grayer color in each case, are calcareous, and have a somewhat
greater amount of colloidal clay than the surface soils. Highly calca-
reous bedrock from which the soils are derived occurs at depths of 2 to 4
feet. Both soils normally occur on a gently sloping surface, but occa-
sionally on fairly steep slopes. The Diablo soils are shown on the Recon-
noissance map, but the Altamont soils were included with the Diablo
series, being described as soils of a browner color than typical Diablo.

Bul. 552] Soils op Western San Diego County 17

The Altamont series has fine sandy loam, clay loam, and clay types, while
the Diablo series has clay adobe types. The clay loam types are shallower
and more subject to erosion than the clay types. The heavier types are
fertile but more difficult to till owing to their stickiness when wet and
hardness on drying.

Subgroup c, Calcareous Soils and Siibsoils. —

Ayar series

Linne series

The Ayar series has brown soils and subsoils, while the Linne series
has dark gray or dark brownish-gray soils and subsoils. The lime con-
tent is high in both the surface soils and subsoils, and the latter usually
contain pieces of marly bedrock from which the soils have been derived.
The upper part of the parent bedrock, which is usually found at depths
less than 3 feet, is soft. The extremely granular structure of the soils and
subsoils seems to mask the heavy texture and causes them to appear
lighter than a clay or clay loam, which a mechanical analysis proves
them to be. Both soil series occur on the higher coastal plain region on a
flat to gently sloping surface. The soils have a high moisture-holding
capacity, are sticky when wet, but are friable at the ordinary field mois-
ture content, due to the flocculating effect of the lime present in the soil
mass. Good yields of grain, grain hay, and beans are secured when
sufficient rain falls.

In the Reconnoissanee Survey the Linne was included in the Monte-
zuma series, with the Ayar described as a browner inclusion. They do not
properly belong with the Montezuma, which is derived from different
parent material and has noncalcareous surface soils as well as other
differences in profile characteristics.

GROUP II, UNWEATHERED SECONDARY SOILS

Group II consists of unweathered secondary soils formed by deposits
of recent alluvial material, occurring in river valleys and on alluvial
fans or alluvial slopes.

Subgroup a, Noncalcareous Soils and Subsoils. —
Hanf ord series
Tujunga series
Laguna series

Soils of the Hanf ord and Tujunga series are derived from granites,
while the Laguna is derived from coastal-plain material of sedimentary
origin. All occupy recent alluvial fans and flood plains and have deep,
sandy, permeable soils and subsoils. They have been deposited under
conditions of good drainage and have no accumulation of alkali or lime.

18 University of California — Experiment Station

The Hanford soils are of a light brown or brown color in surface soil
and subsoil. The surface soils are generally sandy loams and the subsoils
often stratified with alternating layers of sandy loams and sands. The
soil material is all highly micaceous, of medium to low moisture-holding
capacity and of fair to good organic content. They are of a high pro-
ductive capacity and suited to a wide range of crops.

The Tujunga soils are of light gray or light brownish-gray color and
of coarse texture, the fine sand type predominating. They usually border
present stream channels, being of very recent deposition. The soils are
raw, often excessively permeable, of low moisture-holding capacity and
of low organic content, all of which renders them of somewhat less pro-
ductive value than the Hanford.

The Laguna soils are light brownish gray in color generally of loamy
sand or sandy loam texture. They are generally of somewhat lower pro-
ductive capacity than the Hanford series because the soil material
had its origin in the poorer, sandy coastal plain material of leached
character.

Hanford and Tujunga soils were so mapped in the Reconnoissance
Survey. Owing to their small extent the Laguna soils were included with
the Yolo series, from which they differ in being of lighter color and of
poorer quality.

Subgroup b, Calcareous Soils and Subsoils. —

Foster series
Cajon series
Agueda series
Alviso series

Soils of the Foster and Cajon series are derived from granitic outwash
material under conditions of restricted drainage with an accumulation
of lime from calcareous waters. They are often saline in the lower-lying
areas.

Foster soils are of dark brownish-gray color, while the Cajon series
are light gray. Cajon soils usually border stream channels, are of light
sandy texture, low moisture-holding capacity and subject to overflow.
These factors limit their agricultural use. The Foster soils are of medium
texture, have a moderate organic content, hold considerable moisture,
and are utilized for alfalfa, field, and truck crops. In general they are
not adapted to fruit culture because of the drainage and alkali problem.
The Cajon series was included with the Hanford in the Reconnoissance
Survey.

The Agueda soils occur on outwash from the dark-colored calcareous
soils of the Linne series. Both surface and subsoils are of dark brownish-

Bul. 552] Soils of Western San Diego County 19

gray or dull-gray color, of loam, clay loam, or clay texture, granular
structure, and high moisture-holding capacity. This soil is well drained,
contains no alkali, and is adapted to field crops. It is extensively used for
beans. The Agueda was mapped as the Dublin in the Reconnoissance
Survey. It differs from the Dublin in lime content, as well as in other
features, such as origin.

Alviso soils occupy low tidal marsh land that has been derived from
mixed rock material. They are of dull brownish-gray color and are rather
variable in texture and to a large extent have been reworked by the
action of the tides as the water moves in and out of the lagoons. They are
poorly drained and highly saline, and therefore of little value at the
present time. Ultimately certain areas may be reclaimed by building
levees and then leaching with fresh water. The Alviso series was included
with Tidal Marsh in the Reconnoissance Survey.

GROUP III, SLIGHTLY TO MODERATELY WEATHERED
SECONDARY SOILS

Group III consists of slightly to moderately weathered secondary soils
from alluvial or coastal plain materials, with subsoils slightly or mod-
erately denser and heavier in texture than surface soils.

Subgroup a, Noncalcareous Profile; Leached Marine-Terrace Soils. —
Marina series
Elkhorn series

The Marina and Elkhorn series are the result of weathering of sandy
coastal-plain deposits immediately joining the shore line. Both have
sandy surface soils of light brown, medium brown, or light grayish-
brown color. When moist the soils appear to be of a reddish-brown color.
The surface soils are low in humus, somewhat leached, and slightly to
moderately acid in reaction. Subsoils are of about the same texture as
the surface, of yellowish-brown color, but more dense. Subsoils of the
Elkhorn series are more compacted than those of the Marina series and
represent an older, more maturely weathered development. Elkhorn sub-
soils when dry appear semicemented and are somewhat difficult to pene-
trate with a pick or shovel.

These soils are being utilized for avocados, bulbs, flowers, and winter
vegetables. Because of their nearness to the ocean, climatic conditions
seem ideal. The surface soils are friable and easy to till, but lacking
somewhat in humus and general fertility. Barnyard manures, bean
straw, and commercial fertilizers are extensively used in supplying this
need. The Marina and Elkhorn soils were included with the Kimball

University of California — Experiment Station

series in the Reconnoissance Survey, but the detailed studies brought
out many differences in profile characteristics. These two series have
recently been mapped in Monterey County.

36
3 46

E 60

IU Vista

Q sandy

loam,

PER CENT TOTAL CLAY

10 20 10 20 10 20 30 10 20 30 10 20 30 4C

lib-

Han ford

sandy

loam,

Greenfield
sandy
loam,

Ramona

sandy

loam,

Merriam

sandy

loam,

group la group Ha grouplllb group Ulb group IZc

Olivenhain
loamy
fine sand,
group EZb

Fig. 8. — Total clay content of selected soils in each group by horizons. Note
that the clay content in the subsoil of the Eamona sandy loam is considerably
greater than that in the same horizon of the Greenfield or Hanford sandy loams.

PER CENT COLLOIDAL CLAY

0JP_Z0 10 2 10 20 10 ZO 102030 10 20 50 AC

CO
LU

O |2
~ 24
2: 36

H 60
S 7Z

Hi,

Vista

sandy

loam.

Hanford Greenfield Ramona
sand_y sandy sandy
loam, loam, loam,

Merriam

sandy

loam.

groupla grouplla g roup ILT b group nib groupLYc

Olivenhain
loamy
fine sand,
group Ub

Fig. 9. — Colloidal clay content of selected soils in each group by horizons (the
same soils are in fig. 8). The colloidal clay content in the subsoils increases with
the maturity of the soils. The moderately weathered Eamona sandy loam has a
much greater content of colloidal clay than the unweathered Hanford sandy loam.

Subgroup b, Noncalcareous Soils and Subsoils. —
Greenfield series
Ramona series
Hames series
Botella series
Soils of the Greenfield and Ramona series are derived from granitic
parent material and represent two stages of soil weathering beyond the
immature Hanford series. Both soils are brown in color and highly mica-

Bul. 552]

Soils of Western San Diego County

ceous. Greenfield soils have a slight accumulation of colloidal clay and a
moderate degree of compaction in the subsoils, while the Ramona soils
have the greater accumulation of colloidal clay and the denser and more
compact subsoil characteristic of an older soil (figs. 8 and 9). Consid-
erable colloidal glazing in cracks and on the faces of lumps and clods is
in evidence in the Ramona subsoils, but is absent from the Greenfield.

Fig. 10. — Eecent alluvial soils of group II in foreground,

Eamona soils of group III on the terrace, and primary

soils of group I on the hills. Note the erosion

on the terrace.

The colloidal clay content in the B horizon of the Greenfield is usually
about 7 per cent, while the same horizon of the Ramona has from 12 to
16 per cent of colloidal clay. Surface soils are predominantly of sandy
loam texture. The Ramona soils occur on terraces or elevated benches
(fig. 10), while the Greenfield lie on alluvial fans or lower alluvial ter-
races. The soils are well drained, readily penetrated by water or plant
roots, and are considered desirable for a wide range of crops. Both
are valuable citrus soils of southern California. The Greenfield series was
included with the Ramona or Hanford soils on the Reconnoissance map.
The Hames soils are of brown or light brown color and similar in age
and general profile development to the Ramona series, but are derived
from material of mixed geological origin and lack the micaceous par-
ticles and quartz grains found so abundantly in the Ramona profile.

22 University of California — Experiment Station

The surface texture is a sandy loam. Agriculturally, it has about the
same value as the Ramona and Greenfield soils. It was included with the
soils mapped as the Kimball series in the Reconnoissance Survey, but
was established as a distinct series in the more recent surveys.

Botella soils are derived largely from coastal plain sedimentary mate-
rial of nonmicaceous character and are of dull grayish-brown or dull
brownish-gray color. The profile shows a slight accumulation of colloidal
clay in the subsoil along with a moderate degree of compaction. The C
horizon is made up of variable-textured, friable alluvial soil material
extending to more than 6 feet in depth. Normally these soils occur on
well-drained alluvial slopes or low terraces, although in a few places
slightly mottled subsoils are an evidence of local poor-drainage condi-
tions. The soils are well supplied with organic matter, contain no alkali,
and are considered very desirable for general field and truck crops.
Three types are mapped in the detailed surveys, Botella loamy sand,
Botella fine sandy loam, and Botella sandy clay loam. The first two
sandier types are easier to till than is the sandy clay loam, which has a
higher colloidal clay content, rendering the soil sticky and plastic when
wet. The Botella soils were included with the Dublin in the earlier Re-
connoissance Survey. They differ from the Dublin in being of lighter
color, having denser and more colloidal subsoils, and in other profile
characteristics.

Subgroup c, Noncalcareous Surface Soils and Calcareous Subsoils. —

San Marcos series
Salinas series
Sorrento series
Farwell series
Commatti series
Clear Lake series

Soils of the San Marcos series are derived from granitic or micaceous
rocks and are of dark brownish-gray color. Subsoils are of the same
color or slightly darker, mottled, highly calcareous, and only slightly
heavier in texture and slightly more compact than the surface. San
Marcos soils are subject to overflow and to poor drainage conditions dur-
ing the winter and spring months. Alkali is present over a large portion
of these soils, which along with poor drainage limits agricultural de-
velopment. Loamy fine sand and fine sandy loam types have been map-
ped in the recent detailed surveys. This series was included with the
Foster in the Reconnoissance Survey but in the recent surveys has been
differentiated on the basis of the noncalcareous surface.

Bul. 552] Soils of Western San Diego County 23

The Salinas series has soils of dull brownish-gray or dark grayish-
brown color with a slightly weathered profile, and moderately calcareous
subsoils. These soils have their origin in a variety of rocks. Types of
sandy loam, fine sandy loam, loam, and sandy clay loam texture have
been mapped in the surveys. All are considered of high value for truck
and field crops because they are fertile and easy to till and irrigate. They
have good drainage and do not contain alkali. Frost conditions limit cer-
tain crops in some of the narrow valleys where the soils are located. Soils
of this series were mapped in recent surveys in Monterey and San Luis
Obispo counties. In the Reconnoissance Survey they were included with
the soils mapped as Yolo.

The Sorrento soils are similar in profile to those of the Salinas series,
differing in being of light brown or brown color and derived from allu-
vial material mainly of sedimentary rock origin. Subsoils are light
brown, slightly compact, with a slight clay accumulation, and slightly
calcareous. The series is developed on smooth valley floors and slopes on
which drainage is good. The soils are of good moisture-holding capacity
and fertility and with irrigation and favorable temperature are adapted
to a wide range of crops. In the Reconnoissance Survey they were
mapped as the Yolo, but are now recognized as a new series similar to
the Yolo series but developed under lower rainfall and having a slightly
weathered profile with a slight accumulation of lime. Only one type, the
Sorrento clay loam, has been mapped in the detailed areas.

The structural development, compaction, and lime content in the sub-
soils of the Farwell series are about the same as in the Sorrento and
Salinas, but the soils differ in being of dark brown color and in being
derived largely from basic material. They occupy alluvial fans and ter-
races along the coast between the mouth of Horno Canyon and Laguna
Beach, where there is considerable outwash from schistose material. The
gravelly sandy loam type has been mapped. The soil has about the same
value and is used for the same crops as the Sorrento and Salinas series.
As with the others, the series was included with the Yolo of the Recon-
noissance Survey.

The Commatti series is characterized by dull gray to brownish-gray
surface soils and slightly compact and heavier-textured calcareous sub-
soils of about the same color. The soils are derived mainly from calcare-
ous sedimentary rocks and occupy alluvial fans and low terraces of
similar position to the other soil series of this subgroup, although of
somewhat greater age as evidenced by the heavier-texture subsoil. Sur-
face soils are of sandy loam texture, friable, easy to till, and of a good
moisture-holding capacity, although they are low in organic matter.

University of California — Experiment Station

Where climatic conditions are favorable, these soils are adapted to a
wide range of crops. They were included with both the Yolo and Dublin
series in the Reconnoissance Survey.

The Clear Lake soils are of mixed origin and have a dark gray or black
surface soil, an upper subsoil of about the same color, but of slightly
heavier texture, moderately compact and with some lime accumula-

Fig. 11. — Bedding gravelly sandy loam (group IV), east of Del

Mar, showing gravelly and cobbly substratum, shallow

depth of soil, and low brush cover.

tion, and a lower subsoil of light brownish-gray or dull brownish-gray,
slightly mottled, calcareous clay loam. Surface soils are of loam or sandy
clay loam texture. They occupy flat benches or stream bottoms and have
poor subdrainage, which makes them not so well adapted to development
as the other soils of the subgroup. Surface soils are well supplied with
organic matter and are absorptive and retentive of moisture. The Clear
Lake series was included with Dublin in the Reconnoissance Survey,
but is now separated, mainly because of the lime content in the subsoils.

GROUP IV, WEATHERED SECONDARY SOILS

Group IV consists of weathered secondary soils from old alluvial or
coastal plain materials with heavy clay subsoils. These soils usually occur
on terraces of the coastal plain.

Bul. 552]

Soils of Western San Diego County

Subgroup a f Acid Soils and Acid Subsoils, Thoroughly Leached. —
Redding series

The Redding soils are characterized by a light reddish-brown surface
layer of gravelly sandy loam, sandy loam, or stony sandy loam texture
5 to 10 inches thick and a subsoil layer of deep red, compact clay 10 to
20 inches in thickness that rests on a thick cobbly cemented hardpan-like
substratum. Often a true hardpan of red silica and iron-cemented mate-

Fig. 12. — Profile of Olivenhain loamy fine sand, group IV. Note the

columnar (solonetz) B horizon and the consolidated C

horizon consisting of marine sediments.

rial with many imbedded rounded stones 1 to 4 inches in diameter rests
directly on top of the thick substratum. Often a layer of highly colloidal,
drab-colored clay overlies the hardpan (fig. 11). All horizons are dis-
tinctly acid (pH 4.4 to 6.0) . This represents one of the most acid soils of
the state. Redding soils occur on high flat-topped mesas and are derived
from material of mixed origin that has been maturely weathered. The
shallow depth and the high content of gravel and stone limit the use of
these soils. The stony sandy loam type includes steep, eroded areas in
the Poway Hills and has a high content of stone. These steeper areas
were included with rough broken land in the Reconnoissance Survey.
Redding types are of very low value.

26 University of California — Experiment Station

Subgroup b, Noncalcareous Soils and Subsoils Resting on a Partially

Consolidated Substratum (Solonetz-like Soils). —

Olivenhain series
Las Flores series
Tierra series

These coastal plain soils are developed on old marine-terrace deposits
and have surface soils that are friable, permeable, and of loamy fine
sand, fine sandy loam, sandy loam, or loam texture. The surface soil at a
depth of 6 to 10 inches rests abruptly on an extremely waxy tenacious
clay or sandy clay layer that has a definite columnar or solonetz-like
structure on drying (fig. 12). This is slowly permeable to water and
difficult of penetration by roots. When moist, it is extremely sticky and
when dry very hard. From 85 to 95 per cent of the clay content of the
solonetz horizon is colloidal (fig. 13) . The clay layer rests directly on the
moderately consolidated sandstone-like marine substratum at a depth
of 12 to 36 inches from the surface. Surface soils are slightly acid (pH
6.0 to 6.6), while the clay layer is decidedly basic (pH 7.1 to 8.5). The
parent material contains a moderate amount of sodium chloride and
other soluble salts (0.02 to 0.20 per cent). The leached surface, the
heavy impervious clay layer, and the saline parent material cause these
soils to be of low agricultural value. After the heavy rains during the
winter of 1931-32 serious drainage problems have become evident on
these soils with severe damage to permanent crops such as citrus and
avocados. They are also very badly dissected by erosion in certain areas,
exposing the clay subsoil or the parent material (fig. 15).

The three series may be distinguished by color. The Olivenhain has
light brown surface soils and dull brown subsoils ; the Las Flores has
light gray surface soils and dull brown subsoils ; while the Tierra has
dull brownish-gray surface soils and dull brown subsoils. The parent
material of the Las Flores series is of somewhat lighter color than that
of the Olivenhain and Tierra. It is of a light gray sandstone-like nature
(fig. 15).

On some of the steeper slopes the light gray surface of the Las Flores
rests directly on the gray sandstone-like parent material without any
clay horizon lying between the surface soil and the parent material.

The Olivenhain is a new soil series recognized for the first time in the
Oceanside area. The Tierra was recognized as such for the first time in
the Salinas area in Monterey County. Since then it has been mapped in
the Paso Robles, San Luis Obispo, and Santa Ynez areas in California.
These soils were all included with the Las Flores soils of the Recon-
naissance Survey.

Bul. 552]

Soils of Western San Diego County

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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

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 *

■

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

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. (Unpublished
at the time this is written.)

University of California — Experiment Station

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Bul. 552]

Soils of Western San Diego County

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34 University of California — Experiment Station

R2.W.

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Fig. 18. — Grouping of soils of Oceanside 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.

Bul. 552]

Soils of Western San Diego County

soil type, inherent soil characteristics are considered, such as the depth,
texture, and density of the surface soil and subsoil, reactions, alkali con-
tent, and drainage conditions. The rating covers the entire area of each
soil type as occurring in these surveys, and in applying it to an hidi-

ng. 19. — Grouping of soils of Capistrano Area, San Diego and Orange counties,
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.

vidual body of the soil on a farm, the index rating may have to be raised
or lowered slightly because of local abnormal conditions.

On the basis of this rating, the soils have been placed in six grades as
indicated in the table, there being a range of about 20 index points within
each grade except the last. This gives a considerable range in the index
rating of the soils within each grade. Figures 17, 18, and 19 show the dis-
tribution of these grades in the areas. The soils of grade 1 are scattered
irregularly throughout the region in small valleys. There is a narrow
belt of soils of grade 2 along the coast bordering the broad band of grades

36 University of California — Experiment Station

4 and 5 soils which occupy the mesa-like areas of old marine terraces
along the coastal plain. Irregular-shaped bodies of the soils of grades 2
and 3 occupy the upland area between the mesas and the mountains,
interspersed with large areas of grade 6 material. The last is nonagri-
cultural because of its stony character and mountainous topography.

SUMMARY

The Reconnoissance Soil Survey of the San Diego Region and other
generalized soil surveys of southern California, the Sacramento and San
Joaquin valleys, and the San Francisco Bay Region, show the soils in
rather inclusive groupings. The reconnoissance surveys are now being
supplanted by detailed soil surveys as rapidly as facilities permit. These
detailed soil surveys 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.

During 1929 and 1930 three detailed soil surveys were made covering
the western half of the area surveyed in the Reconnoissance Soil Survey
of 1915. Forty different series of soils are mapped in the detailed studies,
while there are eighteen soil series in the Reconnoissance Survey.

The different soils in the San Diego County areas are discussed under
four main groups separated on the basis of maturity of profile and mode
of formation. These have been subdivided into subgroups on the basis of
reaction of the soil mass. Soil series in each subgroup have fairly similar
agricultural values.

Group I : Primary soils are formed in place by the weathering of the
parent bedrock or substratum on which the soils rest, and occur on the
rolling to mountainous topography east of the coastal plain. The Fall-
brook, Vista, Konokti, Escondido, Las Posas, Carlsbad, and Ysidora
series of soils have noncalcareous profiles; the Altamont and Diablo
series have noncalcareous surface soils and calcareous subsoils ; and the
Ayar and Linne soils have both surface soils and subsoils calcareous.

Group II : Unweathered secondary soils are formed by deposits of
recent alluvial material. The Hanford, Tujunga, and Laguna series have
noncalcareous soils and subsoils ; the Foster, Cajon, Agueda, and Alviso
series have calcareous soils and subsoils.

Group III : Slightly to moderately weathered secondary soils are de-
rived from alluvial or coastal plain materials and have subsoils slightly
or moderately denser and heavier in texture than the surface soils. The
Marina and Elkhorn series have sandy leached marine-terrace soils
which are the result of weathering of sandy coastal-plain deposits imme-

Biil. 552] Soils of Western San Diego County 37

diately joining the shore line. The Greenfield, Ramona, Hames, and
Botella series have noncalcareous soils and subsoils; while the San
Marcos, Salinas, Sorrento, Farwell, Commatti, and Clear Lake series
have noncalcareous surface soils and calcareous subsoils.

Group IV : These are weathered secondary soils from old alluvial or
coastal plain materials. These soils usually occur on terraces and have
extremely heavy clay subsoils. The Redding series has highly acid soils
and subsoils. The Olivenhain, Las Flores, and Tierra series have non-
calcareous surface soils and heavy clay subsoils that rest on a partially
consolidated substratum at a depth of 1 to 3 feet from the surface. The
Aliso, Huerhuero, Stockpen, Merriam, and Montezuma series all have
a nodular accumulation of lime in the lower subsoils and a parent mate-
rial of less consolidated nature than that of the Olivenhain, Las Flores,
and Tierra series. The Monserate series has noncalcareous surface soils
and calcareous subsoils which rest on a hardpan or hardpan-like sub-
stratum. With the exception of the Redding series all the soils in this
group have solonetz characteristics.

The soils mapped in the El Cajon, Oceanside, and Capistrano detailed
soil surveys have been evaluated on a comparative basis designated as
the "index of soil value" and expressed as percentage. This rating is
based on the soil characteristics which govern their agricultural value,
such as the depth, texture, and density of the surface soil and subsoil,
reactions, alkali content, and drainage conditions. On the basis of their
index values the soils have been graded into 6 grades : excellent soils,
good soils, fair soils, poor soils, very poor soils, and miscellaneous non-
agricultural materials.

ACKNOWLEDGMENTS

The writer wishes to acknowledge the assistance of Professor C. F.
Shaw and Professor W. W. Weir of the College of Agriculture in the
preparation and editing of this manuscript. The field work and the in-
spection were done in cooperation with the United States Department
of Agriculture Bureau of Chemistry and Soils represented by Mr.
E. J. Carpenter, Soil Surveyor; and Mr. Macy H. Lapham, Western
Inspector.

38 University of California — Experiment Station

GLOSSARY OF SOIL TERMS

Acid soil:* a soil that is deficient in available bases, particularly calcium, and that
gives an acid reaction when tested by standard methods.

Acid igneous origin: soils having their origin in material from the disintegration
and decomposition of igneous and metamorphosed igneous rocks high in quartz
(granites).

Accumulated lime: lime that has been developed or accumulated in a soil horizon
through natural soil weathering processes.

Alkali soil:* a soil containing any soluble salts in sufficient amount to cause injury
to economic plants.

Alkaline soil:* a soil containing an excessive amount of the alkaline (in true chem-
ical sense) salts, usually sodium carbonate.

Alluvial soil:* soil formed from materials transported by flowing waters and de-
posited as alluvial fans and flood plains.

Amorphous structure :* a soil of fine texture having a massive or uniform arrange-
ment of particles throughout the horizon.

Basic igneous origin: soils having their origin in material from the disintegration
and decomposition of igneous and metamorphosed igneous rocks low in quartz
(such as basalts).

Calcareous soil:* a soil containing sufficient calcium carbonate to effervesce when
tested with weak hydrochloric acid.

Colloidal clay: The finer or ultra-clay particles. Wherever used in this report clay
particles are assumed to be less than 0.005 millimeter in effective diameter and
colloidal clay less than 0.001 millimeter in effective diameter.

Columnar structure :* a natural arrangement of the soil mass in more or less regu-
lar columns separated by vertical cleavage planes, and usually broken by hori-
zontal cracks into sections with longer vertical than horizontal axes.

Concretions: small rounded nodules, usually made up of concentric layers, and of
hard consistence, and ordinarily not larger than a pea. The most common con-
cretions are cemented by lime or iron.

Consistence :* soil consistence is a term expressing the degree of cohesion of the
soil and the resistance opposed to forces tending to deform or rupture the ag-
gregates. Common terms in use to express consistence are loose, friable, soft,
hard, dense, compact, impervious.

Cubical structure : the natural arrangement of the soil mass into more or less regu-
lar cube-shaped blocks having the vertical and horizontal axes nearly equal.

Granular structure:* aggregates varying in size up to 2 centimeters in diameter,
of medium consistence, and more or less subangular or rounded in shape.

Hardpan:* a horizon of accumulation that has been thoroughly cemented to an
indurated rock-like layer that will not become soft when wet.

Horizon or soil horizon:* a layer or portion of the soil profile more or less well de-
fined, and occupying a position approximately parallel to the soil surface.

Horizon A :* the upper horizon of the soil mass, from which material has been re-
moved by percolating water, the surface soil. This horizon is generally sub-

* Terms marked (*) are taken from: Shaw, C. F. A glossary of soil terms.
American Soil Survey Association Bui. 9:23-58. 1928.

Bul. 552] Soils of Western San Diego County 39

divided into two or more subhorizons, of which A is not a part of the mineral
soil, but is the accumulation of organic debris upon the soil surface. Other sub-
horizons are designated as A a , A 2 , etc.

Horizon B :* the horizon of deposition to which materials have been added by per-
colating waters, the subsoil. This horizon may be divided into several sub-
horizons designated as B l7 B 2 , B 3 , etc.

Horizon C :* the horizon of relatively unweathered material underlying the B
horizon, the substratum. The C horizon, while often described as unweathered
usually shows some modification in the upper portion and may have several sub-
horizons. In most cases it represents a parent material similar to that from
which the soil was formed. In some cases a stratum or geological formation of
material different from that of which the soil was formed may underlie the soil.
With such conditions there is actually no true C horizon, the B horizons resting
directly on unrelated material. In actual practice, however, this is usually called
the C horizon, its character and lack of relation to the soil being brought out in
the descriptions.

Immature soil:* a soil having a profile with compact subsoil horizons with distinct
clay accumulations; moderately weathered immature soil.

Marine soil:* soil formed from materials deposited by the waters of oceans and
seas, exposed by elevation of the land or by the dessication of the sea.

Mature soil:* a soil having a profile with a compact highly colloidal dense clay
subsoil horizon or a cemented rock-like hardpan horizon; fully weathered ma-
ture soil; the end product of weathering under the existing conditions; a climax
soil in dynamic equilibrium with its environmental factors.

Maturity: stage of development of soil weathering or soil age, shown by the
horizon development of the profile.

Mechanical analysis:* a laboratory process of separating the soil into groups of
grain sizes, used to determine the textural composition of soils.

Micaceous soil : a soil containing visible mica particles, usually derived from acid
igneous rock sources.

Mixed origin: soils which have their origin in material from mixed or undeter-
mined rock sources.

Moisture equivalent : a laboratory method of determining the moisture-retaining
power of soils. It may be defined as the percentage of water retained by a soil
after centrifuging in a standard moisture-equivalent machine under standard
conditions. It provides a basis for laboratory comparison of the moisture-hold-
ing capacity of different soils. The moisture equivalent has been found to ap-
proximate closely the field moisture capacity for medium-textured soils.

Nut structure :* compact aggregates, more or less rounded in shape, of hard to
medium consistence and usually from % to 4 centimeters in diameter.

Parent material:* see horizon C.

Primary soils:* soils developed through the disintegration and decomposition of
rocks in place and the weathering of the resulting debris to true soils with
definite horizons of eluviation and illuviation; residual soils.

Profile or soil profile:* a vertical section of the soil from the surface into the
underlying unweathered material.

* Terms marked (*) are taken from: Shaw, C. F. A glossary of soil terms.
American Soil Survey Association Bul. 9:23-58. 1928.

40 University of California — Experiment Station

Recent soil:* a soil having a profile without definite horizons of eluviation or illu-
viation ; relatively unweathered recent or very immature soil. Eeeent soils usually
are secondary soils composed of recently deposited transported materials, there
being no evidence of any downward migration of clay, lime, or other material,
no evidence of differences in the degree of weathering of the minerals at vary-
ing depths, and no indication of any changes in structure of the soil.

Residual soil:* see primary soil.

Saline soil:* a soil containing excessive amounts of the neutral or nonalkaline
.salts, usually chlorides and sulfates.

Secondary soils:* soils developed through the accumulation and weathering of
materials, originating from previously existing soils and from rock debris, that
have been eroded from their former locations and redeposited by the transport-
ing agents (alluvial, aeolian, glacial, etc., soils).

Sedimentary origin: soils having their origin in the disintegration and decomposi-
tion of material from sedimentary rock sources such as sandstones, shale, and
limestone.

Semimature soil:* a soil having a profile with compact, semicemented horizons
with high clay accumulations; strongly weathered soil.

Soil series:* a grouping of soils having the same character of profile (the same
general range in color, structure, consistence, and sequence of horizons), the
same general conditions of relief and drainage, and usually a common or similar
origin and mode of formation. The name of the series is taken from the region
where the first member of that series of soils was discovered, as, for example,
Hanford series.

Soil morphology : that part of soil science dealing with the form, arrangement,
structure, and other characteristics of the soil mass in its natural condition in
place.

Soil structure:* structure is a term expressing the arrangement of the individual
grains and aggregates that make up the soil mass. The structure may refer to
the natural arrangement of the soil when in place and undisturbed, or to the
soil at any degree of disturbance. See "granular," "nut-structure," "adobe," and
"columnar."

Soil texture:* texture is a term indicating the coarseness or fineness of the soil;
the amount or quantity of each of the grain-sized group of particles that con-
stitute the soil. As the soil is usually made up of particles of widely varying
size, the textural terms usually express the mass effect or the combined effect
of all these grain sizes, but they indicate the predominance (in quantity or in
textural effect) of a certain group of grains.

Soil type:* a soil which throughout the full extent of its occurrence has relatively
uniform texture of the surface soil and relatively uniform profile characteristics.
It is the unit of soil mapping. The name of the soil type is a combination of
series name and the textural grade designation, as, for example, Hanford
sandy loam.

Solonetz soil: soil which has a heavy-textured B horizon containing much colloidal
clay in a highly dispersed state, and which on drying breaks up into vertical
columns (columnar structure), which are usually rounded on the top and may
be capped by a grayish layer, usually thin. The transition between the surface

* Terms marked (*) are taken from: Shaw, C. F. A glossary of soil terms.
American Soil Survey Association Bui. 9:23-58. 1928.

Bul. 552] Soils of Western San Diego County 41

soil (A horizon) and the heavy-textured columnar layer is very abrupt, both in
physical and chemical characteristics. American soil literature has stressed the
morphological characteristics of the solonetz rather than its chemical makeup.
In Eussian literature, a solonetz soil is defined as having slightly acid surface
soil, with the sesquioxides and clay removed from the upper horizon (A) to the
B, the absorptive complex partly saturated with sodium, and the soluble salts
and carbonates in the lower B 2 or B 3 horizons.

Subsoil:* see "horizon B."

Substratum:* see "horizon C."

Surface soil:* the upper horizon or surface layer of the soil mass, the horizons
above horizon A 2 . In describing cultivated soils, it usually includes that por-
tion that is modified by plowing and other tillage operations.

Textural grade:* a classification of soils based on texture alone.

Transported soil:* soil formed by the consequent or subsequent weathering of ma-
terials transported and deposited by some agency such as water, air, or ice;
secondary soils.

Typical profile:* a profile definitely representative of a soil series, the standard
of the type or series, as established by careful field study.

Weathered profile:* a soil profile which has been changed by soil weathering pro-
cesses; a profile having eluvial and illuvial horizons.

Young soil:* a soil having a profile with slightly compact subsoil horizons, but
with little evidence of clay accumulations; slightly weathered immature soil.

* Terms marked (*) are taken from: Shaw, C. F. A glossary of soil terms.
American Soil Survey Association Bul. 9:23-58. 1928.

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