THE LIBRARY

OF

THE UNIVERSITY

OF CALIFORNIA

LOS ANGELES

UHIVEB8ITY OF CALIFOBNIA PUBLICATIONS

COLLEGE OF AGRICULTURE

AGRICULTURAL EXPERIMENT STATION

BERKELEY, CALIFORNIA

THE EFFECTS OF ALKALI
ON CITRUS TREES

BY

W. P. KELLEY AND E. E. THOMAS

BULLETIN No. 318

January, 1920

DIVISION OF SUBTROPICAL HORTICULTURE

COLLEGE OF AGRICULTURE

BERKELEY. CALIFORNIA

UNIVERSITY OF CALIFORNIA PRESS

BERKELEY

1020

EXPERIMENT STATION STAFF

HEADS OP DIVISIONS

David P. Barrows, JMi.l)., LL.D., President of the University.

Thomas Forsyth Hunt, Deau,

Kdward J. WiCKSON, Horticulture (Emeritus).

Walter Mulkord, Forestry, Director of Resident Instruction.

Herbert J. Webber, Director Agricultural Experiment Station.

B. H. Ckocheron, Director of Agricultural Extensioru
Hubert E. Van Norman, Vice-Director; Dairy Management.

James T. Barrett, Acting Director of Citrus Experiment Station; Plant Path-
ology.
William A. Setchell, Botany.
Myer E. Jaffa, Nutrition.
Charles W. Woodworth, Entomology.
Ralph E. Smith, Plant Pathology.
J. Eliot Coit, Citriculture.
John W. Gilmore, Agronomy.
Charles F. Shaw, Soil Technology.

John W. Gregg, Landscape Gardening and Floriculture.
Frederic T. Bioletti, Viticulture and Enology.
Warren T. Clarke, Agricultural Extension.
John S. Burd, Agricultural Chemistry.
Charles B. Lipman, Soil Chemistry and Bacteriology.
Clarence M. Haring, Veterinary Science and Bacteriology.
Ernest B. Babcock, Genetics.
Gordon H. True, Animal Husbandry.
Fritz W. Woll, Animal Nutrition.
W. P. Kellby, Agricultural Chemistry.
H. J. Quayle, Entomology.
Elwood Mead, Rural Institutions.
H. S. Reed, Plant Physiology.
L. B. Batchelor, Orchard Management.
J. 0. WiiiTTEN, Pomology.
Frank Adams, Irrigation Investigations.

C. L. Roadhouse, Dairy Industry.

P. L. Griffin, Agricultural Education.
John E. Dougherty, Ptjultry Husbandry.
S. S. Rogers, Olericulture.
L. J. Fletcher, Agricultural Engineering.
Edwin C. Voorhies, Assistant to the Dean.

CITRUS EXPERIMENT STATION

Division ok A(iKicuLTURAL Chemistry

W. P. Keli.f.v *A. B. Cummins

E. H Thomas S. M. Brcavn

* ResiyiUMl .June 1, 191>».

SB

THE EFFECTS OF ALKALI ON CITRUS TREES*

By W. p. KELLEY and E. E. THOMAS

INTRODUCTION

It is generally believed that citrus trees are especially sensitive to
alkali. One of the best known investigations on the effect of alkali on
citrus was published by Loughridge in 1898.^ In this paper it was
pointed out that orange trees may be severely injured by the use of
saline irrigation water. From studies on certain groves near Corona,
California, it was found that severe injury had been produced as a
result of irrigating with saline water from Lake Elsinore for a period
of from three to four years.

Analysis of the water showed it to contain 917 parts per million
sodium chloride (common salt), 377 parts per million sodium sulfate
(glauber.salt), and 391 parts per million sodium carbonate (black
alkali). Loughridge concluded that the injury to the trees was due
directly to the corrosive action and puddling effect of the black alkali
and indirectly to the antiseptic action of tlie sodium chloride on the
bacterial processes of the soil.

The effects were more pronounced in certain groves than in others.
Inherent differences in the soil apparently exerted an influence on the
depth to which the water penetrated and, therefore, caused the salts
to accumulate in greater (quantities in the upper layers of the soil of
certain groves than of others. On the whole, the effects were roughly
proportional to the concentration of the alkali salts that had accumu-
lated in the zone occupied by the roots of tlie trees.

The results of this investigation indicated that citrus trees are
quite sensitive to alkali, and tluit the length of time a given supply
of saline irrigation water may be used without producing injury
depends mainly on the rate the injurious constituents accumulate in
the layei's of soil occupied by the roots of the trees.

In 1900 Ililgard- pointed out that citrus trees are especially sensi-
tive to sodium chloride. He called attention to the previous work at

* Paper No. 53, University of California, (iraduato Scliool of Tropical Ai;ricul-
ture and Citrus Experiment Station. Kiverside, Calif.

1 Effect of Alkali on Citrus Trees. Annual IJeport, Calif. A<ir. Exp. Sta.
1897-8, pp. 99-113.

2 Nature. Value and Utilization of Alkali Lands. Calif. Act. Exp. Sta. Bull.
128 (1900j. p. 28.

209908

306 TNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

Corona in wliich it liad boon found that 2520 pounds per acre of
sodium chloride distributed throuj;h the soil to a depth of four foot,
caused an orange tree to become completeh' leafless, while another
tree nearby, wiiere the soil was similar in other respects, but contained
only 720 ])ounds ]K'r acre of sodium chloride, was much less severely
injured. "Here it is apparently the excess of common salt to which
the difference is duo."

In 1901 LougluMdge'' culled attention to the extreme sensitiveness
of the lemon ti'oe. He said: "Tlie lemon seems to be the least tolerant
of all of the fruit trees, for it was stunted by 1440 pounds common
salt per acre, distributed througli four feet depth, and was killed
by 1900 pounds combined with 1900 pounds carbonate of soda."

In harmony with the conclusions of Loughridge and Hilgard,
recent investigations by the writers have shown that different varieties
and species of citrus trees are quite sensitive to alkali, especially so
in the case of the lemon, and that after a few years irrigation with
saline water, botli lemon and orange trees may be severely injured.
Again, it has been found that the effects produced by a given supply
of impure irrigation water may, for a time at least, be extremely
variable even in different portions of the same grove. Part of this
variability, as shown below, is probably due to differences in the
depth to which the water penetrates, which in turn affects the rate at
whicli the salts accumulate in the root zone.

Experienee in various localities has shown that, under certain
conditions, continued irrigation with comparatively pure water also
tends to hasten tlu' accumulation of injurious amounts of soluble salts.
Several hundred tliousaiid acres located in different parts of Califor-
nia, whicli were free from injurious amounts of alkali previous to the
introduction of irrigation, have since become veritable alkali lands.
Seepage, togctlicr with a rising water table incident to over-irrigation,
have been the ])rineipal means by whicli tlie salts have been brought
u]i from below and deposited near the surface. Small areas of citrus
gi-oves liave ali'eady become heavily charged witli alkali by this means.

In the course of investigations on the nutrition of citrus trees, we
have dt'voted considerable study to certain phases of the alkali prob-
lem. Early in this work, it became evident that the existing state of
knowledge was inade(iuate. The symptoms of alkali injury have not
l)een recognized clearly. The relations of fertilizers to the problem,
and esjiecially the elfet-t of ajiplying irrigation water containing alkali
salts, are inadecjuately understood and appreciatid.

3 Tolerance of Alkali l)v Various Cultures. Calif. A-^r. Exp. Sta. Bull. 133
(1901), pp. 14-1(>.

Bulletin 318 the effects OF ALKALI ON CITRUS TREES 307

It is commonly held that alkali injury is mainly, if not entirely,
due to excessive concentration as such. In the course of this work,
it has become evident, however, that injury may be produced under
certain conditions where the total concentration is relatively low.
The data obtained in a study of this phase of the subject afford the
basis for an interesting hypothesis whicli will be presented elsewhere
and further work is in progress. The discussion in this bulletin will
be confined mainly to the effects of exc( ssive concentration.

As this work has progn ssed, it has become increasingly evident
that many of the citrus growers of California have not sufficiently
grasped the significance of alkali in citrus culture. Especially is this
true in regard to the bearings of impure irrigation water on the
accumulation of alkali in the soil. Fortunately, a large percentage
of the citrus soils was free from alkali previous to the introduction of
irrigation and very much of it still remains free. There are con-
siderable areas located in several districts, however, where harmful
amounts of alkali have accumulated as a result of applying saline
irrigation water and still other areas, not yet seriously injured, where
alkali is accumulating at present as a result of orchard practices which,
if continued, will ultimately produci' injury.

This bulletin will be devoted to a discussion of results obtained in
connection with a study of a considerable number of citrus groves in
different localities in California. The investigations reported herein
deal mainly with the effects of alkali rather than with means of over-
coming the injury. It is undoubtedly a matter of practical importance
for citrus growere to be able to recognize the effects of alkali and
especially to appreciate the relationsliips between existing orchard
practices and the accumulation of alkali.

Unfortunately, the present state of knowledge does not yet make
it possible to predict with as great a degree of certainty as is desirable,
what the effects of a given amount of alkali will be, or how long a given
saline irrigation water may be apj)lied before producing injury. The
extreme variability of soils and the inade(iuaey of knowledge concern-
ing the fundamental relationships between salts and soils, and salts
and plant growth, add to the difficulty. Desi)ite these facts, informa-
tion of some practical im])ortanee has been obtained.

The investigations reported herein should be looked upon as being
preliminary to a study of methods of eonibatiiig alkali in citrus
groves. It is hoped that this discussion will enable citi-us growei-s to
recognize the effects of alkali, to apjin ciatc Ihc sci-imisness of alkali
m citrus culture, to apprelieiid mow cleai'ly 1h(> relationships between
irrigation and the aceunuilatioii of alkali, and to sec that the aiii)liea-

UiVlh^l'N Ot- SUblHuI'lCAL HORTlCULTUKt
' OP AGRICUl" ^

308 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

tion of certain fertilizers, especially nitrate of soda, may, under certain
conditions at least, bear a very important relation to the accumulation
of alkali. Witli this knowledfje, it is hoped that practical citrus
growers will be able to adjust their irrigation and fertilizer practices
in such a way as to retard the further spread of alkali and thus
prevent its accumulation in many groves that have, as yet, not been
seriously injured.

SYMPTOMS OF ALKALI INJURY

DiflPerent varieties and species of citrus trees are affected differently
by alkali. Lemon trees show the effects by a pronounced yellowing
of the margins and burning of the tips of the leaves, followed by
unusually heavy shedding of the leaves in the latter part of the winter
and spring. The subsequent new growth may appear to be quite
normal and vigorous for several mouths, but later a large portion of
the leaves turn yellow in irregularly sliaped areas around the margins
and fall excessively. In the presence of excessive concentrations of
salts, especially chlorides, complete defoliation may take place. Mottle
leaf frequenth' occurs, and sometimes chlorosis. Both the quality and
quantity of the fruit are impaired.

Orange trees also show the effects of alkali in different ways. On
certain soils, mottle leaf is one of the first symptoms. In some locali-
ties, the older leaves assume a brownish hue and tend to curl slightly.
Rather sudden defoliation takes place, especially when excessive
amounts of chloride occur, followed later by a profuse growth of new
shoots. The leaves of the new growth are likely to be undersized and
paler in color than normally. With especially high concentrations of
sulfates and bicarbonatcs in the soil, orange leaves become chlorotic
and strikingly similar to that condition referred to by Hilgard* as
occurring on highly basic soils. The smaller twigs may be killed.
Frequently the leaves are abnormally small on one portion of a tree,
and full-sized on others.

Premature shedding of the leaves takes place with both oranges
and lemons affected by small amounts of alkali, which may be pro-
tracted throughout tlie greater part of the winter mouths, thus greatly
reducing the number of leaves remaining on tlie trees at the close of
the dormant ])eriod. Navel oranges are more sensitive than Yalencias,
and Eureka lemons more sensitive than Lisbons. In general, lemon
trees are more sensitive than orange trees. Neither orange nor lemon

■1 Marlv subsoils and tlic Clilurosis or Yellowing of Citrus Trees. Calif. A^.
Exp. Sta.'Cir. Xo. 27 (lOOC).

Bulletin 318 the effects OP aekaei on citri's trees 309

trees reach their usual size on soil that contains injurious amounts of
alkali.

It has been found that oran«:e trees affected by alkali are unusually
susceptible to injury from adverse climatic conditions. Hot winds
burn the- young leaves and frosts produce more serious injury than
with normal trees. Alkali injury is also accentuated by the lack of
care, such as improper tillage, the insufficient use of manure or other
fertilizer, and withholding irrigation, tlicrcby allowing the soil
to become too dr3\ If the soil by allowed to dry out excessively, the
concentration of alkali in the soil moisture may become harmful,
while a more abundant supply of water would so dilute the salts
present as to reduce the concentration to a point where normal growth
could take place.

THE EFFECTS OF IRRIGATION WATER

Despite the wide publicity that has been given the subject of
irrigation waters and the many analyses that were published by
Plilgard in the reports of the California Station, our studies in the
different citrus districts suggest( d the desirability of making a survey
of the irrigation water in use at present. oMore than a thousand
samples have been analyzed. It has been found that the vast majority
are practically free from alkali. Especially is this true of the water
that is drawn from points located near the large watersheds, such, for
example, as the Sierra Nevada and the San Bernardino mountains.
Usually the wells that are located near tlie course of streams that
originate in those mountains are also sufficiently pure.

On the other hand, wells located at some distance from the large
watersheds and relatively large streams that tliemselves originate
directly in the mountains, show a wide range in eomposilion. A con-
sideral)le iuiml)er of such wells contain notable amounts of salts.
These are widely distributed over a considerable number of citrus dis-
tricts in several counties. Tn certain localities the dissolved salts are
predominantly chlorides, others sulfates and in still others biearbon-
ates. A few wells have been found to eontaiji large amounts of
nitrates.

The results of this survey ai-e, on tlie whole, in elose agreement
with the ])ul)lished conclusion of Dr. llilgard. We (piote from him
as follows:'"'

"The investigations made by tlie Station have sliown that aside
fnmi the freipiently saline cluiivieter of the well and even the artesian

M'alif. Agr. Exp. Sta. Iliill. 128 (IDOO), p. :il.

310 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION

waters of the iictrolciim bearino: regions of the State in tlie coast
ranges, the streams of that region, especially the smaller ones, are
sometimes too strongly charged with alkali (in this case largely the
snlfates of soda and magnesia) to be snitable either for irrigation
or domestic nse. Towards the end of the dry season, even the larger
streams of the southern coast ranges, with their diminished flow, some-
times show an excess of salts. Tliis seems also to be true of the San
Jacinto river, which feeds Elsinore Lake." On the other hand, he
says: ''The wati'rs flowing from the Sierra iNIadrc, south of the
Tehachapi range, are tliroughout of excellent ([uality for irrigation
purpos(>s, as are all those flowing from the Si(>rra Nevada. The same
is true of the artesian waters of the valley of southern California, from
Los Angeles east to Redlands."

A considerable number of groves that have been irrigated with
saline water have been under close observation for one or more years.
As a means of securing information on the effects, soil samples, drawn
with a one-inch soil tube, have been analyzed and wherever possible
adjacent areas that have been irrigated with comparatively pure
water, or virgin soil, have also been sampled. Some of the results are
submitted below, together with analyses of the irrigation waters that
have been applied.

The analytical results are expressed as parts per million of the
soil or water. In contrast to previous publications, we have not
attempted to estimate the amounts of the several salts present. The
state of present knowledge does not make it possible to determine
definitely the actual amounts of the different salts that occur in com-
plex mixtures, such as irrigation waters or soils. By analysis the
components of the different salts may be determined, but while vari-
ous schemes have lieen employed for calculating the amounts of salts
present, all of them are more or less arbitrary and have little justi-
fication in modern cliemistry. Accordingly, the analytical data are
submitted as determined without calculating the theoretical salt com-
binations.

The analyses recorded in table 1 have been chosen to show the
wide range in e()m]iosition found among tlie irrigation supplies. Some
of these contain large aniounls of salts, othei's lesser amounts. As
will 1)(' ]ioiiit('d out more fully below, the effi'cts of some of these
waters liave been extremely injurious. Sample No. 84 represents suit-
able water. This sam])le, drawn from wells loeat( d near the San
Bernardino ^Mountains, fairly represents the main supplies of moun-
tain water of southern California, the effects of which have been
entirelv satisfactorv.

Bulletin 318 r|,jjj^ EFFECTS OF ALKALI OX CITKIS TREES 311

It is not necessary to discuss the amounts of, and variations among,
the individual constituents of these waters. Casual observation of
tlie analyses will suffice to show tiuit there is a v/ide range of difference
in the content of total dissolved materials and that a number of the
individual constituents occur in certain samples in relatively large
amounts. The most significant differences in these watei's probably
lie in the chlorine and sodium. The unusually high nitrate content
of sample No. 119 is a matter of special interest. Where such water
is used for irrigation, it is highly improbable that nitrogenous ferti-
lizers will be needed.

The variations f(mnd among sami)les that contain relatively large
amounts of salts, such, for example, as Nos. C42 and 643, are probably
of little practical significance. On the other hand, samples Nos. 103
and 105 contain still greater amounts of salts, especially so in the
case of the latter. Sample No. 150 is of intermediate composition and
represents a type of water that is being used at present on several
thousand acres of citrus in California. As will be pointed out later,
the use of this water on a lemon grove for a period of approximately
twenty years, produced definite injury.

The numbers of pounds of a given constituent that will be added
to the soil by an irrigation water may be readily calculated from the
analysis. For example : an acre foot of water, No. 119, which contains
1479 parts per million soluble solids, will supply the soil 3993 pounds
of solids, while an acre foot of No. 84, containing 222 parts per million,
will add only 599 pounds. In view of the fact that the amounts of
water ap])lied varies widely in different localities and in different
years in a given grove, it is not ]K)ssible to state the exact amounts
of salts that have been added to the soil in a given case. It is only
possible at present to make qualitative comparisons among the groves.
It is evident, however, that large amounts of alkali nuist necessarily
have been adth d to the soil where such water as Nos. 119, 642 and 643
have been applied. Still greater amounts nnist have been added in
a given period witli Nos. 103 and 105, while with No. 150, tlie rate of
salt addition has been considerably less.

During the past eight years, several hundred acres of orange
orchards located near Riverside, which were previously irrigated with
suitable water, have be<']i irrigated with saline water similar to samples
Nos. 119, 642 and 643. Other groves adjacent 1o these have been
irrigated from the beginning with eouiparatively pure water (No.
84). So far as can now be detei'inined, the soil in this innnediate
locality was i'easona])ly unii'oi'm and i'vvv from alkali previous to
planting the orcliai'ds. Tlie soil is of a sandy loam cliaractei', reason-

312 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION

ably deep and free from hardpaii. Throughout this district, the
soil is deficient in organic matter and nitrogen, the liberal application
of both of which is required for successful citrus culture.

The orange trees are about twenty-four years old. A number of
these groves have been under close observation for a period of about
three years. A large portion of the trees irrigated with the saline
water have already been severely injured ; some of them are almost
dead and a large portion unprofitable. The degree of the injury is
much more pronounced at the present time (1919) than it was in 1917,
while in 1916 injurious effects had scarcely begun to appear. The
•accompanying photographs, plates 1 and 2, illustrate the effects and
show the appearance of the trees in the spring of 1919. They show
the striking contrast between the effects of good irrigation water and
water containing alkali salts. In portions of the groves where the
saline water has been applied, excessive defoliation has taken place
several times. ]\Iany of the smaller branches have died and the new
foliage has shown excessive mottle leaf.

Soil samples from a number of these groves have been analyzed.
Some of the results are submitted in tables 2, 3, 4, 5 and 6. The data
show that the total soluble salt content of the soil and the amounts of
certain individual constituents have been greatlj^ increased as a result
of irrigating with saline water. The chlorine and sodium content have
been increased to the greatest extent. Other constituents have also
been augmented considerably.

The data show a direct relationship between the salt content of the
soil and the composition of the irrigation water, and the condition of
the orange trees is positively correlated with the salt content. It is
evident, however, that orange trees are extremely sensitive. The total
concentration of soluble matter in a number of the samples was not
more than 0.10 per cent (1000 parts per million), even where the trees
have been severely injured. The soil samples represent composite
mixtures of a considera])le number of cores, taken at random from the
spaces between tlie trees where the irrigation waters have been applied.
Under the prevailing system of furrow irrigation soluble salts tend to
accumulate in greatest amounts between the irrigation furrows and in
the unirrigated spaces between the trees, owing to lateral movement.
Consequently, higher concentrations ])robably occur in localized areas
between the furrows, tlian were found in the samples analyzed. Wliile
orange trees are more sensitive to alkali tlian many other crops, it is
reasonably certain tliat with tlie coiitiiuied use of these waters the
soil will become so heavily charged with alkali as to impair its useful-
ness for the more resistant crops.

Bulletin 318 the EFFECTS OF alkali on CITRl'S TREES

313

The data in tables 4, 5 and 6 show that the salts have evidently
penetrated to considerable depths. Samples were taken in three groves
to a depth of seven feet, two of which have been irrigated with saline
water (No. 643), the other witli comparatively pure water (No. 84).

Fig. 1. — Orange trees irrigateil witli saline water, Xo. ()4."

Fig. 2.— C;...M^, 1,^>-^ i.r.^aK.i ,\it:, ;4,..,. v>„M,. :x,.. >>-f.

Tlie analyses estal)lisli the fact tliat the salts have penetrated deejily.
The data su<i'<i'('st that the jx'iicti'ation has even reaelied det'i^er than
s(>V(Mi feet, but sniiiples have not been di'awn fi'oni ui'cater dei^ths.

The analyses of samples from the (lifrcreiit ^n-oves that have been
irri^-a1(>d with pure water indicate that the oriu-iiuil soil must have
varied considerably. The variations are not surprising', liowever, since

314 UNIVERSITY OF CALIKORNIA — EXPERIMENT STATION

the difforoiit groves from which these samples were taken are located
considerable distances apart. It may be mentioned in passing, tliat
more or less mottle leaf occnrs in many of the groves in this locality
that have been irrigated with comparatively pure water. In such
cases, the cause of the mottle leaf inheres in the soil itself. Consider-
ably more mottle leaf occurs in grove E than in groves M or S. It
is interesting to note that the soil of the former differs considerably
from that of the two latter. Further discussion on tliis point will bo
submitted elsewhere.

In addition, tlie vertical distribution of salts varies in different
groves under the same saline irrigation supply. (Compare the data
from groves 0 and C, tables 4 and 6.) It is not possible at present to
explain these variations. Differences in the amounts of water applied,
in cultural operations and in tlie degree of compactness of the subsoil,
are probably among the most imjiortant factors.

While large portions of tlusc groves have been severely injured,
it is interesting to note that tiie effects have not been uniform over
the entire area that has been irrigated with saline water. In some
places, little or no effects were evident in 1918, and again in 1919
the degree of injuiy was still much h ss pronounced in certain places
than in others. It is important, however, that some of the trees which
were healthy in 1917 have since begun to show" definite signs of injury.
Soil samples have been drawn from among the severely injured trees of
the grove (B) and from an area of the same grove where the trees
have been only slightly injured. Analyses of these samples are
submitted in table 7.

The results show that the subsoil below the second foot of the
severel}' injured area contains considerably more salts than in the less
injured portion. Especially is this true of the chlorine and sodium,
the two constituents that seem to be most responsible for the injury
in these groves. These variations are probably due to inherent differ-
ences in the physical nature of the subsoil which are such as to modify
the rates of ])enetration and accumulation of salts. At any rate, it is
interesting that the more severe injury has taken place where the
greater amounts of salts liave accumulated. As already pointed out,
the least affected jiortions of this gi-ove have now begun to show definite
injui'y. It is liighly probable that the injury will become severe over
tlu^ entiri* orchai'd if tlie use of the ])resent irrigation supply be not
discontinued. '' > iil

As bearing further on the variability of the effects of saline irriga-
tion water, studies have been nuule on the chemical reactions that take
place when salts are added to soils. It has been found that alkali salts

Bulletin 318 the effects OF alkali ox citrcs trees 315

have the power of reacting witli lieavy tyi)es of soils to a greater degree
than with sandy soils. The reactions result in removing limited
amounts of sodium from solution and bringing into solution corre-
sponding amounts of other bases, composed mainly of calcium. The
physical arrangement of the soil particles also undergoes alteration.
In view of the fact that soils are extremely variable, it is not surpris-
ing, that the efi'ects of irrigation have not been uniform over a given
grove.

Analyses of two irrigation waters from Tulare County are also
reported in table 1 (Nos. 103 and 105). They contain unusually
large amounts of salts. Information at hand does not made it possible
to state the exact length of time these waters have been applied. The
wells from which the samples were drawn were deepened about four
years previously and there is some evidence that water of a radically
different character was obtained as compared with that originally
supplied. It is probable that one of these wells (No. 103) supplied
fairly pure water previous to being deepened. The orange trees to
which these waters have been applied are approximately twelve years
old and have shown severe injury during the past two years.

Soil samples were drawn from these groves and also from adjacent
unirrigated fields apparently similar in every way to the soils in the
groves. One of these has been used for grain for a number of years,
the other still remains in its native state. The soil of one of these
groves (T) is of a sandy loam character most of which is underlaid
with a dejLse hardpan at a depth of from two to three feet. The other
is located on the heavy type of soil, belonging to the Porterville clay
loam adobe series, locally knowii as "dry bog." The analyses are
reported in tables 8 and 9.

The data confirm the results obtained in tlie study of the groves
located near Kivcrside. By comparing the irrigated witli the unirri-
gated soils, it is seen at once that the irrigation has greatly increased
the amounts of soluble salts in the soil. While the concentration of
practically eveiy constituent has been increased, the chlorine and
sodium have been increased to the greatest extent. Comparison of the
soil analyses witii those of the irrigation waters shows that those con-
stituents jireseiit in tlie water in greatest amounts have accumulated
in the soil to the greatest extent. The rates of iiierease, Jiowever. are
not proportional to the eompositioii of tlie irrigation water, owinir in
part, at least, to the fact that citrus ti-ees al)sorb large amounts of
certain constituents, and only small aiuduiits of otliei-s. As will l)e
shown elsewhere, citrus ti'ets do not absorb sodinni salts to anv ureal
extent, but absorb relatively large amounts of calcium.

DIVISION Of SUHIKliPirAl HORIICULIUK^
COLLEGE OF AGRICULTURE

316 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

It is iiilcn'stintj to note in this coiiucction that navel orange trees
are l)ein<2: <i:r()wn on one j)ortion of each of these groves, and Valencia
oranges on anothei-. In eaeii ease, the navels were injured in a
sliorter jx'riod of time than the Vali'neias. In faet, some of the Valen-
eias of grove T, located in a portion of the field where the soil is six
or more feet deep, have not as yet been severely injured, but even that
l^ortion of the Valencia trees located on sliallow soil similar to the
luivel area have been less severely injured than the navels. In grove
II, tlie Valrfncias were much less severely injured in 1918 than the
navels. It is important to state, however, that many of the Valencia
trees in the latter grove have shown seven; injury in 1919. These
facts, together with observations in other localities, indicate that
Valencia oranges are more resistant to alkali than navel orange trees.
But it must not be concluded tiuit the former are highly tolerant of
alkali, for such is not the case. The use of irrigation water containing
alkali salts will ultimately produce iiijuiy to either variety, it being
mainly a matter of the length of time.

A lemon grove located near San Diego luis also been studied. The
trees are about sixteen years old and have been irrigated from the
time of planting witli saline water No. G89. During the past two or
three years, a portion of the trees have shown signs of injury, many
of them severely so. ]\Iost of the older leaves throughout the grove
have turned yellow around the nuirgins and brown at the tips. A
large proportion of the leaves have fallen in certain places, the smaller
shoots have di( d and the economic value of some of the trees has been
greatl}' impaired.

Referring again to the table of water analysis, it will be seen that
the irrigation water (table 1, No. 689) contains considerable amounts
of alkali salts, being composed in this case largely of sodium chloride.
Soil sam})les were drawn from tliis grove to a depth of two feet
and also from an adjacent unirrigated field. Their analyses are given
in tal)le 10. In harmony with the results ah'eady discussed, it is shown
that the concentration of salts has been materially increased as a
result of irrigation. Tlie luuisually high soluble potassium content
of the first foot of the irrigated soil is especially noteworthy and is
probably due to tlie liberal use of fertilizers and manure.

The irrigation waters discussed above contain relatively large
amounts of salts. Some of them contain amounts of alkali salts that
might reasonably have been cxpeeti'd to produce^ injury. Under the
conditions of soil and subsoil, as they exist in these groves, it would
have been surprising iiuleed to iind that injury had not been produced
bv these waters. It is interesting in this connection that the effects

Bulletin 318 the effects of alkali on citrus trees 317

produced by the irrij^ation waters discussed above are quite similar
to the effects produced at Corona by water from Lake Elsinore more
than twenty years ago. Tlie analyses reported by Lough ridge also
show that the salt content of Lake Elsinore was actually less than
that of some of the present supplies. It would seem that the unfor-
tunate experience at Corona has either been forgotten or largely over-
looked by citrus growers.

In addition to the above and a considerable number of other saline
irrigation supplies, that are at present being applied to certain citrus
groves in California, there is a much larger quantity of the irrigation
water that contains somewhat smaller amounts of alkali salts. In view
of the economic a-spects of this phase of the subject, it is a matter of
interest to study the effects of this latter class of waters. For this
purpose, a lemon grove has been chosen. While the irrigation supply
in this case has been drawn from more than one source, the proportions
of which have varied from time to time, the analysis given in table 1
(no. 150) probably represents the average composition of the water.
It contains considerably less alkali than the irrigation waters discussed
above. As judged by current standards, this water woidd certainly
not be considered to be excessively saline.

The lemon trees, now twenty years old, grew thriftily and produced
heavy crops of fruit for many years. During the past two or three
years, however, some of them have begun to decline. Tiie older leaves
have turned yellow or brown and liave fallen excessively in the winter
and spring. ]\Iany of the trees have lost their former thrift and the
yields and quality of tlie fruit have been considerably reduced, in
spite of the fact that reasonably good care and liberal amounts of
manure and other fertilizers have been applied.

Soil samples have l)een analyzed from tliis grove, and also from
an area near by that has been under irrigation with water from
the same source for only two years. The results are submitted in
table 11. The data show tliat the total soluble matter has been very
materially increased as a result of the longer period of irrigation.
Considerable amounts of sodium salts, composed principally of the
chloride, have accumlated in the soil. Sulfate has also increased
considerably. It is again found that the greatest increases have
taken place among those constituents tliat are absorl.)ed l\v lemon trees
in least amounts and have, at tlie same time, been added in greatest
amounts in the irrigation watei".

As might have been jirt'dieted from the aiuilysis of tlie water, it
has re(|iiire(l a longer period of time 1o et'feet a given iiierease in the
concentration of salts in this grove than has bt'i-n rei^uired wliere some

DIVISION OF SllbiK'iFICAl. HORIlCULIU^f
COLLEGE OF AGRICi:

318 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION

of tlie more liighly saline waters have been applied. The data show,
however, that the alkali eontent of the soil may ultimately reach a
harmful eoneentration whei-e irri<?ation water is applied that contains
only a relatively low eoneentration of alkali salts.

It should not be inferred that the application of water similar to
samjilc No. 150 will always jiroduee the same degree of injury; certain
other lemon groves of ai)i)r()xinuitely the same age have been irrigated
with the same supply as grove (L), which do not, as yet, show any
apparent injury. Samples of soil from these groves have not been
analyzed.

Taken in their entirety, the above investigations show a remarkably
close relationship between the composition of the irrigation water, on
the oiu' hand, and the accumulation of alkali salts and the condition
of the orange and the lemon trees, on the other. In every case we have
studied, where saline irrigation water ha.s been applied for a period
of years, alkali salts have accumulated in the soil and the citrus trees
have been injured in consequence. The rates at which salts have
actually accumulated vary, however, in different soils, depending on
(1) the composition of the water, (2) the amounts applied, and (3)
the freedom with which it penetrated into the subsoil.

It must be apparent from the above discussion that, although the
content of alkali in an irrigation water may not be directly injurious,
the time may come after it has been applied for a period of years,
when exceedingly harmful amounts of salts will accumulate as a result
of evaporation and that sooner or later injurious concentrations may
even result from tlie use of only slightly saline water. The more
freely the water penetrates into the subsoil, the greater will be the
tendency for the salts to be leached down below the roots of plants,
but it must not be concluded that saline water can be applied with
imi)unity to a porous soil, for such is not always the ca.se. Even here
injurious concentrations may accumulate. As will be shown elsewhere,
injur}' may be produced by lesser amounts of alkali in a light sandy
soil than in heavy soil. It should be understood that sufficient amounts
of water to leach the soil effectively are rarely applied in any section
of California and especially is this true in the citrus groves where the
furrow system of irrigation is used and the supply of water is limited.

THE GROWTH OF CITRUS TREES ON ALKALI SOILS

It is ([uitc immaterial, so far as the well-being of citrus trees is
concerned, or of other erojis for that matter, whether alkali be intro-
duced into the soil as a eonstitiu'nt of the irrigation water, or whether

Bulletin 318 the effects of alkali ox citrus trees 319

it accumulate there as a result of other afjencies. The net effects will
be similar, provided the eoncentration and proportions of the soluble
constituents in contact with the roots be the same.

Several grov( s have been studied where alkali salts either occurred
originallj' or have been brought up recently b}- capillarity, due to a
high water table. The results have rev(ahd some information addi-
tional to that set forth above, which seems to be of sufficient interest
to warrant brief discussion.

A twenty-year-old lemon grove located near San Diego, that has
been irrigated with reasonably pure water the greater portion of the
time, has been studied. During the past few years, the trees have
become less thrifty than formerly. ]\Iany of the older leaves have
become yellow or brown in irregularly shaped areas around their
margins and have fallen excessively at certain times. Some of the
leaves are variegated and show the usual symptoms of mottle leaf.
The yields and quality of the fruit have also depreciated.

Soil samples to a depth of four feet have been analyzed, and the
results are iTcorded in table 12. The data show that this soil contains
considerable amounts of soluble salts of which sodium is the predom-
inant basic constituent. In this case, however, a considerable portion
of the sodium, especially in the third and fourth feet, must occur in
combination other than the chloride, since the chlorine content is
insufficient to combine with all of the sodium present. The data indi-
cate that considerable amounts of both sodium sulfate and sodium
bicarbonate occur in the subsoil layers. The water table is many feet
below the surface and it is probable that a large portion of the salts
accumulated in the subsoil previous to modern agriculture, although
the irrigation water may have tended to increase the amounts present.

It is especially interesting that the roots of the lemon trees have
not penetrated deeply in tliis soil, more than 95 per cent of them
being within eighteen inches of the surface. There is probably some
connection between this fact and the higher concentration of alkali
salts found in the third and fourth feet.

The above discussion should not be interpreted to mean that a
definite degree of injury to a given variety of citrus trees can always
be predicted with certainty from a single soil analysis. On the con-
trary, other faetoi-s are evidently involved in tlie problem that have
not yet been fully evaluated. The following discussion is of interest
in this connection.

Local areas occur in a A'alencia orange grove near Garden (irove
in Orange County where many of the ti-ees have been sevei'ely injured
by aJJj/Tli brought up as a result of a tenipoi-arily high water table in

320 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

the winter and sprin*; of 1916. The water table receded within a few
months, bnt the alkali salts remained in the soil. A considerable num-
ber of the trees have recently died, and all of them in certain areas
became excessively chlorotic, following the rise of alkali.

Soil samples have been drawn from an area where the orange trees
have died and also from among healthy trees near b}^ the analyses of
whieli are submitted in table 13. The results show that a high con-
centration of a inimber of salts occurs where the trees have died.
The amounts of chlorine, sulfate, sodium and calcium are all excessive,
extremely so in the case of sulfate. The concentration is undoubtedly
])rohibitive to orange tree growth.

On the other hand, the concentration of soluble sodium in the soil
where the trees still remain healthy is ver}' much greater than was
found in some of the orange groves where severe injury has been pro-
duced by saline irrigation waters. In this case, however, the sodium
occurs largely as sulfate and bicarbonate, whereas the chloride pre-
dominated in tlu^ former case. On the wliole, the results obtained in
this investigation indicate tliat sodium chloride is much more toxic
to citrus trees than sodium sulfate or sodium bicarbonate, which is in
agreement with the conclusions of Hilgard.

An eight-year-old Navel orange grove near Bakersfield, portions
of which have been severely injured by alkali, has also been studied.
Analysis of soil samples (table 14) reveals a very high concentration
of salts where the trees have been severely injured. With the excep-
tion of the first foot of this soil, the concentration of chloride is not
excessive, but sodium sulfate occurs in large amounts. Unusually high
nitrate also occurs in the first foot. This soil is also supplied with
large amounts of soluble calcium, the nuiin portion of which occurs
as tlie sulfate (gypsum). Extremely large amounts of gypsum occur
in the third, fourth and fifth feet.

The analysis again sliows a high soluble sodium content in the soil
where the orange trees are normal, but again the clilorine is low. In
the first three feet, the sodium is largely comb-ined as bicarbonate.
In the second and third feet, considerable amounts of the normal
carbonate of sodium also occur.

It will be noted that the fourtli, fifth and sixth feet of this soil
contain extremely higli concentrations of soluble salts, composed
mainly of calcium sulfate and sodium sulfate. The roots of the
healthy trees are largely confined to the upper two feet of this soil,
and so long as they remain there and the alkali does not rise, it is
possil)le that satisfactory growtli will result. It is highly probable,
however, that the salts will tend to rise as a result of capillarity and

Bulletin 318 tjj^ effects of alkali on citrus trees 321

every precaution should be taken to reduce evaporation to the lowest
point possible and thereby retard the rise of salts.

It should be pointed out that a luimber of the soils studied, where
citrus trees have been severely injured by alkali, contain abundant
supplies of the usual plant foods. The soluble potassium, nitrate and
phosphate have been found to be present in abundance in a number
of those soils. It is highly improbable, therefore, that the lack of
plant food has contributed to the unhealthy condition of the trees,
or that the use of commercial fertilizers will effectively overcome the
injury. However, it should be stated that there is some evidence that
an abundant supply of plant food does enable citrus trees to overcome
small amounts of alkali. On the other hand, it is reasonably certain
that no amount of ordinary fertilizer will be able to rejuvenate the
trees where large amounts of alkali occur.

THE EFFECTS OF SODIUM NITRATE

Investigations at the Rothamsted Station in England, at the Penn-
sylvania Station in this country, and elsewhere, have been interpreted
to mean that the continued application of sodium nitrate contributes
to the formation of carbonates in soils. The presumption has been
that sodium carbonate is formed through the selective absorption of
the nitrate (NO.,) ion by the crop and the union of the sodium with
the ubiquitous carbon dioxide of soils. We are not awar£ that this
assumption has been conclusively proved, the published evidence being
more suggestive than conclusive.

While we deem it to be highly desirable to know just what com-
pounds actually exist in a given soil, and recognize that dissimilar
effects are likely to be produc(>d by different salts of the same base,
it is nevertheless true that any salt of sodium is an alkali salt. In view
of the possibility, as suggested above, that sodium nitrate may con-
tribute to the formation of sodium carbonate (black alkali) in soils,
a substance commonly regarded as injurious to plant life, and that
there is evidence that citrus trees may be abnormally affected by
high concentrations of sodium, whatever its combination, it is of inter-
est in this co7inection to study the effects of sodium nitrate.

Relatively large amounts of sodium nitrate have been applied to
citrus groves in different localities in California. Tiie fertilizer plots
of the Citrus Experiment Station at Riverside afford material for the
study of tlie effects. One of these ])lots (H) lias l)een fertilized
exclusively with sodium nitrate for the past twelve years. For the
past six years, approximately 900 pounds iiave been applied per acre

322 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

per annum. Prcvioush', and cspocially durinj^ the first few years of
the experiment, lesser amounts were applied. The total amount that
has been applied as an aggregate for the twelve years is 7944 pounds
per acre. While the amounts applied have undoubtedly been exces-
sive during the past five years, as is shown by the soil analysis, the
amounts of nitrogen ajiplied are not in excess of that sometimes
applied by practical citrus growers, who occasionally apply as much
as 1000 pounds of sodium nitrate per acre during a single season.

The control plots (B) and (I\I) lie adjacent to the sodium nitrate
})lot. Each plot contai)is six Navel and six Valencia orange trees, and
six Eureka and six Lisbon lemon trees. All of them have been irrigated
and cidtivated as nearly alike as passible. During the first five or six
years of the experiment, the growth of the young trees of each variety
was markedly stimulated by nitrate of soda. The soil is notably
deficient in organic matter and nitrogen and the successful culture of
non-leguminous crops requires the addition of considerable nitrogen.

While the growth of the trees was notably stimulated by sodium
nitrate during the first few 3'ears of the experiment, and healthy,
normally appearing trees were produced, since that time excessive
mottle leaf has appeared on every tree in this plot. The mottling here
became so severe during the past two or three years as to render the
trees wholh' unprofitable. No marketable fruit whatever is now
produced by these trees.

Soil samples from the control and sodium nitrate plots, taken to
a depth of six feet in June, 1919, show the effects that have been
produced (table 15). The composition of the soluble matter in the
soil has been greatly changed as a result of applying nitrate of soda.
The total soluble matter has been increased more than twofold in every
foot section down to and including the sixth foot. Among the indi-
vidual constituents, tlie sodium and nitrate have been most markedly
increased. The bicarbonate has also been increased to a limited extent,
although not greatly, but the soil of this plot has not accumulated
any soluble normal carbonate.

This soil has now accumulated a considerable amount of alkali
merely as a result of applying sodium nitrate as a fertilizer for a
period of twelve years. Its suitability for the growth of citrus trees
has l)een destroyed, or at least seriously impaired. The alkali in this
ease is largely sodium nitrate, a substance of unquestionable value as
a fertilizer in humid climates and possibly so under certain soil and
climatic conditions in the semi-arid west.

Bulletin 318 the EFFECTS OF ALKALI ox citrcs trees 323

THE EFFECTS OF SALINE IRRIGATION WATER AND Na NO, ON THE
REACTION OF SOILS

In view of the widespread belief tijat sodium carbonate (l)laek
alkali) and sodium bicarbonate are the most toxic constituents that
occur in alkali soils and of the possibility tiiat the injuiy to the groves
discussed above may have been due to, or at least associated with,
excessive alkalinity (Oll-ion concentration), the reaction of a con-
siderable number of these soils has been determined by means of the
hydrogen glectrode.

It has been found that the use of saline irrigation waters Nos. 119,
642 and 643, ha.s not increased the alkalinity of the soil over and above
that occurring where good irrigation water has been applied. In each
case, the soil is distinctly alkaline in the chemical sense of the term,
but not appreciably more so where the saline water has been applied.

In the comparisons of unirrigated soil with soil that ha,s been irri-
gated with saline water, it has been found that in two cases, soils T
and Y, there appears to have been an appreciable increase in alkalinity
as a result of irrigation, while in the case of soil II, there has been
a decrease.

In order to study the effects of sodium nitrate on soil alkalinity,
tests have been made on each of the control plots (B and M) that lie
adjacent to the sodium nitrate plot (II) . The results leave some doubt
whether the reaction has been materially changed as a result of apply-
ing sodium nitrate. It should be pointed out, however, that the soil
of each of these plots is distinctly alkaline and it does not follow from
these results that the application of sodium nitrate to an acid soil
might not tend to lower the acidity.

A determination of the reaction of other soils not reported herein
has shown equally as high a degree of alkalinity (OH-ion) where
healthy citrus trees are being grown, as in the severely injured groves.
We are inclined to conclude, therefore, that excessive alkalinity is not
the cause of the injury, either in the ease of saline irrigation waters.
or where sodium nitrate has been applied as a fertilizer. Excessive
concentration of sodium as such, together witli tlie relationships it
bears to the concentration of other constituents ])resent, is prol)al)ly
more fundamentally responsible for the injury.

DISCUSSION

The results of recent investigations establish tlie fact that some of
the irrigation waters in use at the jiresent tinu> on the eitiiis groves of
California are higlily charged with alkali; otiiers contain soniewliat

DIVI540N OF sijfsr.vnri::AL horiiculiuke

COLLEGE OF AGRICULTURE

324 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

lesser amounts, while a much larger proportion contains intermediate
quantities of salts. Fortunately, however, a very large proportion
of the irrigation water is highly satisfactory in quality.

It has been found that a considerale number of citrus groves
located in several districts in California have already been severely
injured by alkali and that a large percentage of the injury is due to
the irrigation water.

The comments of Hilgard made in 1900 relative to the use of saline
irrigation water may be appropriately quoted at this time :"

Means and Gardner" have called attention to the fact that exces-
sively saline irrigation waters have been applied to the soils of certain
portions of the Pecos Valley, New Mexico, and that severe damage has
been produced as a result. In discussing this problem in 1899, they
said : "The soils were shown to contain originally only small quantities
of alkali salts in their natural state, but at present there are areas
containing great quantities of such salts. The presence of this alkali
ma}', in nearly all cases, be attributed mainly to the salt which is
contained in the irrigation water. . . . The character of the water is
the most serious difficulty in the way of profitable irrigation. To
develop a new supply of water would be an engineering problem
difficult of solution. The use of the present supply is attended with
possible loss of crops, especially where the most favorable conditions
do not exist."

Forbes'* showed that the irrigation waters of the Salt River and
other valleys of Arizona are supplying large amounts of salts to the
soils. From soil analj'sis he found that the salt content of the soil
had been materially increased in consequence of applying saline
water.

G Calif. Agr. Exp. Sta. Bull. 128 (1900), p. 30.

It would hardly seem necessary to emphasize specially, the danger incurred in
irrigation with waters containing unusual amounts of soluble salts; since ordinary
common sense clearly indicates the impropriety of increasing the saline contents
of soils already charged with them, by the evaporation, year after year, of large
masses of saline wat«r. Yet experience has shown that the eagerness to utilize
for irrigation whatever Avater happens to be convenient to good lands, often over-
comes both that sense, and Avarning, given ])y the published analyses of such
waters. Without specifying localities, it may be said that great injury has already
been done in California by the disregard of obviously needful caution in this
respect. The very slight taste possessed by glauber salt and salsoda does not
adequately indicate their presence, even when in injurious amounts; so that fre-
quently a chemical test of the waters is the only definite guide.

" A Soil Rurvev of the Pecos Vallev, New Mexico. U. S. Dept. Agr., Report 64,
pp. :5(>-7(5.

■^ The Kiver Irrigating Waters of Arizona — Their Cliaracter and Effects. Ariz.
Agr. Exp. Sta. Bull. 44, 1902.

Bulletin 318 the EFFECTS OF alkali ox citrus trees 325

Chlorides are undoubtedly the most injurious constituents that
occur in the irrigation waters of southern California, but it must not
be concluded that other alkali salts can be ignored. In certain locali-
ties some of the waters also contain injurious amounts of sulfates and
carbonates. Ililgard says, "Unfortunately it is not easy to give abso-
lute rules in regard to the exact figures that constitute an excess of
salts for irrigation purpose s, since not only the composition of the salts,
but the nature of the land to be irrigated, and the frequency of irriga-
tion required, must be taken into consideration." He concluded that
40 grains per gallon (684 parts per million) is the maximum amount
of the total mineral matter a water can safely contain, unless the
mineral constituents be composed largely of gypsum. But he also
said: "When a large proportion of the solids consists of carbonate of
soda or common salt, even a snialhr proportion of salts tJuin 40 grains
might preclude its regular use." We regret to state that a consider-
able number of irrigation waters contain salts in excess of this limit,
some of them greatly so.

It has also been shown that tlie continued application of nitrate
of soda may bring about an increase in the amounts of alkali in the
soil. It is true, the amount of nitrate that has been applied to the
experimental plot we have studied is excessive and the results might
have been different on other soil or even on the same soil, had it been
treated differently in other respects. If nitrate of soda be applied
in moderate quantities to a porous soil, especially where the rainfall
is heavy, or if used in conjunction with manure and cover crops, it
is highly probable that the sodiinn will be leached more deeply than
it has been on the experimental plot at Riverside.

However, it is especially important for farmers to understand
clearly that citrus treses, as well as many other crops, do not absorb
more than ver}' limited amounts of sodium, and that wherever nitrate
of soda be applied, eitlier in combination with other fertilizer con-
stituents or alone, the sodium will, for the most part, be rejected b}- the
crop and left in the soil. This sodium remains mostly in soluble form
and contributes directly to the alkali conteiit of the soil.

All sodium salts are really alkali salts. As has been repeatedly
stated, small amounts of none of them arc injurious, and in the case
of the nitrate, limited amounts undoubtedly stimulate the growth of
practically all crops; but unless drainage' ett'ectively leach the salts
from the soil, the continued application of sodium nitrate, or of saline
irrigation water, will ultimately produei' a hainiful eoneentration of
alkali in any soil.

326 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

It is also a matter of practical importance, that the repeated appli-
cation of any sodium salt to soils, followed by leaching with irrigation
w^ater, or rains, tends to reduce the porosity of the soil and thereby
restricts the movement of the water through it. Sodium carbonate
and sodium bicarbonate probably produce this effect to a greater
extent tiian tiie other common sodium salts, but all of them produce
til is eft'ect to an undesirable extent. The experimental plot to which
nitrate of soda has been applied, has become badly puddled, and the
poor physical condition of the subsoil in a number of the groves where
saline watere have been applied, form one of their striking character-
istics. The surface soil in some of these groves has become exceedingly
baked, so much so as to be readily detectable by merely walking over
it. Hence, the effects of alkali are not wholly determined by the con-
centration of salts in the soil. The adverse physical conditions must
also be considered.

Therefore, wherever nitrate of soda or saline irrigation water
be used in regions of light rainfall, especially if applied for any con-
siderable length of time, it is important for farmers to understand
that the soil must be kept open and porous. Tliis can probably best
be accomplished by growing deep-rooted cover crops and plowing
under organic materials, such as manure or bean straw.

While ordinary irrigation and rains tend to leach more or less
alkali down below the reach of citrus roots and probably accomplish
this end quite effectively in some soils, our investigations show that
the application of saline water has resulted in materially' increasing
the amounts of alkali witliin reach of the roots of the citrus trees. The
soil types and climatic conditions of these groves vary widel}'. Some
of them, not reported above, occur in the districts of comparatively
heavy rainfall and on soils ordinarily considered to be naturally well
drained.

As suggested above, the irrigation supjilies rarely contain enough
alkali to harm citrus trees directly. So far as we have been able to
learn, no detrimental effects occurred in any of the groves until after
the saline waters had been apjilied for a period of years. The injury
came about rather through the concentration resulting from the
accumulated residue, left by the evaporation of repeated applications
of watei', as was pointed out by Dr. llilgard many years ago.

An excess of chlorides causes the tips and margins of citrus leaves
to l)eeome yellow or brown, followed b}- defoliation. Sometimes a large
portion of the haves fall and the young, tendi'r slioots may be killed.
An excess of sulfates and biearbonates, on the other hand, is more
likelv to stunt the growth of the trees and cause the leaves to become

Bulletin 318 ^jik EFFECTS OF ALKALI ON OITRCS TREES 327

chlorotic. More or less mottle leaf may also occur. Lemon trees are
apparently injured by lesser amounts of alkali tiian oranj^cs.

On the whole, the observations and conclusions of Ililj^ard and
Loughridge have been strikingly confirmed. It ha.s again been shown
that citrus trees are quite sensitive to alkali and especially to sodium
chloride. It is a matter of practical importance for citrus growers
to recogni/.e this fact, for sodium chloride is the one constituent most
commonly found in irrigation waters that are drawn from wells in
the citrus sections of California.

As for the treatment of the injured groves, nothing more than the
most general suggestion can be offered at present. AVhere saline irri-
gation water is being apjilied. the first consideration sliould be to
secure an adecpuite supply of i)ure water. In fact, so long as the
application of saline water be continued, it will be difficult to over-
come the harmful etTects by any method that may be devised.

As suggested by Forbes-^ an occasional flooding may improve the
conditions, by leaching the salts below the reach of the roots, but
before flooding be undertaken, tlie irrigator should assure himself
that the subsoil is of such character as will permit deep penetration
of the water and allow it to drain away. Otherwise, his eft'orts will
be wasted. x\fter the salts have been washed down below, the soil
should be thoroughly cultivated in order to reduce evaporation and
thereby check the rise of salts.

Where saline water is the only irrigation supply that can possibly
be obtained, it may be found desirable, in some cases at lea.st, to dis-
continue the furrow system of irrigation entirely and adopt some form
of basin or flooding irrigation instead. By that means, the tendency
will be to leach the salts down into the subsoil and possibly below the
reach of citrus roots. The success of such a scheme will depend largely
on the natui'e of the subsoil drainage and the thoroughness with which
it is executed. In addition, the leaching effects of the winter rains
sliould be taken advantage of to the greatest extent possible. As a
means to this end, the soil should be put into such condition previous
to the I'ainy season, as will prevent surface run-oft' and enabl(> the
rain water to peneti'ate deeply.

It sliould be borne in mind, however, that alkali sails are being
di'iven down into the subsoil and that there is a constant danger of
the salts rising up around the roots. Furthermore, the contimied
addition of such large amounts of salts as occur in some of the irriga-
tion waters, will materiallv inerease the salt content of the natural

•-'Ariz. A>,n-. Exp. Stii. T?ull. 44 (l!t02\ ].i>. Kw 170.

328 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

drainage water. In localities where the volume of the drainage water
resulting from such leaching constitutes any considerable portion of
the natural drainage water, the ground water may ultimately become
heavih' charged with salts as a result. This is especially to be feared
where the ground water is rising or is already near the surface. In
view of these facts, the application of saline irrigation water should
be avoided, whenever possible.

The experience of the growers near (^orona, following the use of
water fnmi Lake Elsinore, is of sjiecial interest at this time. Some
of the groves that were severely injured then, have since recovered
and have borne profitable crops of fruit, while others have not yet
fully recovered. In general, the most effective treatment was found
to consist of thorough tillage, plowing down manure and the applica-
tion of suitable irrigation water.

If good water be applied freely it is probable that the harmful
concentrations of salts that have accumulated will be gradually leached
down below the reach of the roots and the use of manure, coupled with
deep plowing, will gradually restore conditions favorable to growth.
As a means of further increasing the porosity of the soil, an applica-
tion of gypsum may also be desirable. In addition to its flocculating
effect, gypsum, and other calcium salts also, seem to ameliorate the
effects of toxic concentrations of alkali salts, and enable crops to
tolerate concentrations of alkali salts that are prohibitive of normal
growth in the absence of an abundance of calcium salts.

AVhile somewhat apart from this investigation, it may be appro-
priate to state, that a limited study of the amounts of water available
to the citrus groves of California leads us to believe that the most
promising source from which a supply of really good water can be
secured in quantities sufficient to meet the demands of the constantly
expanding citrus industry, can be obtained only througli concerted
effort directed towards the control of flood waters. By the use of
suitable check dams, reservoirs, reforestation, and such otiier devices
as will permit the storage of tiie mountain waters, either above ground
or within the water-bearing gravels, an adequate supply of suitable
water can probably be obtained. At any rate, the excellent water
that falls in the mountains of California, may be so conserved as
to augment materially the volume of water now being obtained from
them, and thereby make it possible to discontiiuie the use of at least
a portion of the saline water.^°

1" A(kii()\\i('(l<,niu'nt is due Mr. A. R. Cuiiiiiiins and Mr. 8. M. Brown for
annlvticTil assistance rendcri'd i7i connection \vith this investi<;ation.

Bulletin 318 the EFFECTS OF ALKALI ON CITRl'S TREES

329

iC Oi 00 O -^ O 'Ci
1^ r^ (M ti "M O QO
(M -H C^ C^l O C<l

^55

CO ro o 1^

t^ CO O GO

c; ^ CO 'T

go

00

o

o

CO

,_i

CO

O

CO

r--

• - a

N.

X

o

CO

(M

(N

CO

'C

'-'

>^

^O

CO

CO

't*

SC^

o
d

^

-2^

3.6

CO

-+<

lO

CO

C5

CO

o

,

S

"aO

CO
"75

*o

*o

c-x

g

c^

t-^

i^

Ol

1-

CO

^

><

-^

oSi

<:;

<3

CO

n

.2

S

'-^

^

Q

■Si

:?;

s

o

H

S

c

o

go

LO

t^

^

CO

o

iQ

IC

>o

W
fa

o

2o

-^

c

.«

CO

■<

*-M

•S^

o

iM

O

•^f

CO

C5

CI

^*.

■-Z

o

gS

r-(

(M

C^

iM

'"'

'"'

<

s^^

cB

»J

1— (

rt

3

>j

m

_^

pq

B

<

p,

^

o

_a

c

CO

rH

CO

t^

r^

t^

CO

o

m

.s

c;_^

^

-a

'C ^

>— 1

lO

o

Ol

i^

t^

CO

o

^

5o

C

t^

-+<

w^

^

o

^^

lO

>o

CD

CO

(M

'^

t-H

m

o

"5 '^

CO

CO

CO

o

CO
03

o

bn

t/3

m^

.Ss

H

2i

O

£

S!

«J

a

Tj

^

5^

O

^

H

X

o

W

>C

a

"S^

s>r

o

.§"?

iC

CO

^

^

00

,^

^

r^

a

D

^ ^

§o

CJ

CO

CO

CO

u

■3''^

■-^

CO

CO

CO

->!

CO

CO

E^

Ol

O)

CO

o <o CO t^ CO

-- O) rt --I rt

CO CO ^ (a t^ C3 '-O CO

"^ C CO -^ CO CO

t<J

'■—, o oi 01

•? " !M O 01 CC >* C; 'O CO

53 (M 1^ -t t^ CO o CO 't

o-^ (M^coocs-roco
Hw rt ,-1 --I ,-1 CO -H

u

t^ CO X X

01 ^ ^ — I

O 'X X >X -* » CO

= = X ^ ^ n' O O X "O
:;/^ ,-HcOco— ii-HCO— 1

DIVISION 0^ SM : Hin<iii,ULlUi^^

COLLEGE OF AGRICUl

r\r e^Asfi t-\i

I r ("xptki I A

330

UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

3 05

O 00 O l^
C^ C<1 CO (N

!M I— ( T-H r-H

.2* t^-^ococofooi

'O^, ^ ^ ^ GO -^ M^ 00

a
'%2

CO ■* C<> c:

iw

2 f^

SO

IfT t^ ^ ^

1^ o ^ ^

S 6D

^ --H (M (M

C^J CM ^ rH

&s

ftf

c!

S

-<!

^

s

CO c^i oo 00

^ CO (M 'O

X

•2ls

ro "O •* o

o I- >o ro

o

^U

6^

< H

i-H to ci.

CM

CO

^

d

CM

Tt<

CO

CM

'c

aO

lO

lO

CO

fe;

Q

c
o

H

^

o

'3

CJ

«

t"^"

ui

«

CM

CO

^

t^

CO

lO

GO

o

.

ci /^

CO

CO

GO

^

H

CM

c^

o

lO

UO

'^

^

•^

m

CM

i-H

o

l>

e

a

<;

^

c

Tt CO CO •*

^

J &

^

^o CO ■* '* CO ■* '^ CO

~72 CO i— I t~-. CO »0 CO CO

o
O

a

IS g

C: C5 c
"N lC C3
C<l CM CM

CO CO ■* CO

to

to

o 00 CO CO

LO CM >— I 1— I
CM CM CM CM

Ba

c
O

CO lO O CO

^^

CM CM C^3 I-H

c

•Jl

O £?

O GO CO i-O O >-0 lO

:i- CO CO O O CO O O
■;_ C^l.— ii— ICOC-ICOCO

~~ OiCGOCOC^ICMCr;
— ^ CMcO^G0C0C0»-O

;= COCMCMi-H^rt^

cT- c; cc CO

i; 6 1^ ~ r^ o
~x c; 01 oj "-o

■^- ^ 01 C^J -H

'^ -:f "* f

lO O O CD

^ X S CO

^-^ ir; i.o ic 'O
-;~ ?i c- CO t

Bulletin 318 'pjj^ kffects OF ALKALI ON CITKI'S TREKS 331

.2,'! O -1' CO 1^ >-0 O — I .= .* CC O "T i>- o o o

.S-' rt rt rt rt e-^ ^ r>| ^ ^j ^j ^ ^

sCi o 'C 1^ c; M o -t

oif GO t^ -^ i^ o r^

«

<-.

U3

H

<

s

K-

^ --^

P-

.— 71

o

X

o

X

re O

X

^O

-fi

C^l

^

c^) -r

o

u^

h

-I^

o

Ci

o

s

00

Si

6

"B.O

I-

;:^

re

—

I- -c

>*

"^

^

o^

«

,s

j^

s

o

^

a

•^

■^

H

^

k^

fa
fa

c
■/2

S

o

.-tex

ro

-

t-

t-

.^ .c

r- —

— C -X -M — ' -H M

o

-—

'S-

Ol

>-<-",--

— _u —

fa

t

Cs

M ~

re »C :e

:c X c:

o

r-

'■

*— «

!-■

X

;jj

r^C

- _

o

-~ "r "tr -i^C v3 '^ S ^ — %J T'

fa :/ "~ W "■ ^ '^

X '^ n^.

i- "a T^ rc rc ?i ?. t^ ?. c5

r ~ -~ — -H rt c-i -M ri ro

^ — — . . - ^ "" 6) re ?t c-i ?i M Ti

o

; — I ri -M re -^ ~ — ' - - -^ "^^ t- -^ ri '" X

•/ v:; X c; X >: c; o ~-7 i^ n i- — _ ti —

C T. _C J- ~ *- _; ^ ;2; _f; .= .h: - -= — -

332

UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

E_

3 OS

to -^ o >o

rH IC CO CO

Y^

1— 1 i-H r-l .— 1

O O GO 00

I— I i-H

en

lO 00

O t^ o

C^ <N

•^ 05 (M

CO (N (N

^ 00 O CO

►:^ o

a

^ tj

aO

w

C

o^

E-

'S

y,

o ^.^

b

«

O

?o

b

Q

S

o

H

.IS

<u__^

Q

|5

H

tc

"SS

i2 5-

oO

CD O

o o

00 O O CO

p-

.^0!

»c

lO

CD (N Tt<

CO CO

CO Ci

lO Tt^ CO ^

;?

JiO

(N

c^

O CO o

cS^

o

o

"^

H

IW

C<l c^

Tf c^

1

IC Tf 'tj* CO

o
2

-2

1

>o

't

6
>

»C (N CO

CO C^ Ol

^

g CD CD

S en CD 00 O

e CD CO t^ i^

cq

~- Tti ^ C<1 l^

e:

^

cq

O

B o d,

<1 ^ 2^~

^2 c

IB

m

o
O

18

>® ^

1>

c3

«i

CO

(N

iM

^H

_s:

Tfl

00

CO

H

1

C^l

I-H

1— 1

05

00

-«

■*

CO

CO

(M

(N

§

CO

"—I

00

VJ c^ t^

CO CO uo

C^ ^ 03
CO (N "-H

O

LO lO Lt o

■- 2

iC lO

t^ CO i-H

CO CO

«0 O 00

Tt< lo CO

C^ CD CD ">)

C^l t^

t^ UO t^ CD

t^ LO

1— I c^ CO -^

Bulletin 318 THE EFFECTS OF ALKALI ON CITRUS TREES

333

3 as

iw

BJ

f.

H

H

^

s

.2-5

!?:

o

u

H

<!

O

QJ

«

rt^

Ig

P.

><

.2

O

^

'a

CJ

<u^^

go

Pk

*~^

^^.

-<

m

?.""

►J .s

o -c

.26

^*

CO
CO

5

0

C5

0

30-

s

^

O £

CO

.&

03 Dh

;^

C

c!^

"^

18
1-

•^

_,

t^

:::i~

tl

-f

t^

H

oc

;m

s^

r^

oc

(M

H

cc

'^

0

c^i

M

■^

tc

i~

Z

s

o

O

(U

r^ iM !M

■M I^ -t<

c^i CO *o

H d

o £

a .0 CL,

b

sfe i. ^ ^ ^

(U « ^

0

a

0

|Xi

?

c3

<»

r^

.-1

Cm

-fc^

z;

ii

C

CO

^

0

c-i

C

0

■^

3

o

«?;

0

C3

"W

00

10

^

-q

X

c^

(N

S

t-

t^

■^ ii.

H

H

^c C-

f}

A

'^

0

0

c;

ii U' X 36

c::

c o

o/i!SION OF SIJbil:'.'rr:AL HORTICULTURE
Sli^UEGE OF AGRirilLTURE

334

UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

OQ

1— I l>- CO >C

•^ (M M ec

.2 * 00 M M IM

■OZ .-H ,-1 CO T)<
Sv ^ (N cc (>>

iC 'f t^ Ol

s«

C5

o >o

o

CO !M '-'

■*

^

c^ <-<

^

CO iM (M

-^

0!

«

P,

w

H

<

>

P-

.S 0]

?-H

o o

^

lO 1— 1 o

o

■ 5^

iC

»o ^

CO

OO O 'O

^

O

o

o

§

a o

CO £

'S. Z.

SCh < ^ _l r-i

GC C': CO CO

c~. cc yj ^ ^^-
t^ l^ '^ to -..

J2 Q 'O 'M T} (N
fc^^ O C"! T^ C"!

c:j

CD

■o X. I- -C

s «

CD

05

05

I^

E^

(N

tl£^-•

o

OS

o

?^

'A

Q

s

i^

.2«

^

1^

C5

C-1

03

■ly

iC

—'

'^

1— 1

«

O

<

M

;^

o

u

S'^

'c.O

iQ

Ol

t^

r-

o

^_^

j:^

C3

CO

I— 1

.-H

H

a

O

_o

C

Z

:^

o

G

s

tH

w ^_^

hS

SJ

2 o

Ol

o

t^

CO

(M

CI.

^7.

00

Ol

c^

I— 1

"-^

<

72

y.^

K

s

S

^

»-^

<;

^

r-i

►ii

•"

o^^

t-3

'<^

.50

CO

o

^

t^

o

a

■=^

r^

o

t^

'^^

^

m~^

'-'

C<1

(N

■-1

o

En

;h

C

?r

a

w

C3^.

Z

""-^

c^

2

^^

CO

r^

^1

T.H

c;

H

^

o5

iC

CO

H

s

tc

z

O

o

O

,

c

o

lO

t^

2

X

X

^J

CO

^

o

o

K

II

^

^1

■*

f— 1

"^■Tl

^

I^

o

lC

■? o X s;

Bulletin 318 xjjj.. i.;pfects op alkali on citrus TREh:s 335

« -

>c lO X CO cc r-- — < o

cc ro o CO 1^ cv ',0 -^

>-c CO TO 01 O C/j 'T Ol

«Ui

o c; •— :c

— O C: r-i >-< ^

(N (M 01 01

5 i; so ^ -t -£ "^ -H ^

2 ^ t^ ^

r~

TJ

>£6

l-H

(D

-|73

^n

Tl'

w

m"'

>J

^

0

cc

17

0

fc

w

"S ^

0

^-^

06

a;

-go

0 ■— -

P

S

H

H

0

a;

c _

0

Jc

U

n

^ CTj c>i

c 00 o o

-t< t^

1.0 I^ 0 'O

0 0^

CO o) cr. CO

"O ^

CO "^ CO CO

o

^ " ^ ^

,9 .i.i' CC '^ C X

'-'- — ■/-' CO f 10 -^

w ~ X

X

»

_

0 ~" c^

1-

OI

CC

1-^ r-<

—

01

— M CO -r

336 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

-oZ ■^OO^COO'O O'-HQ0Ot--t~-

Q

s

as

fa

<^

M

M

U

M

S

<:

.2-5

PQ

CO ^-^

pj

o

-<

a

'^

s

H

»i^

>
O

■g-o

PL,

o

3

S

-<

;-!

o ^^^

«

o

go

Tt<

O

a

•tii^

^

!B

z^

<

c3

n

S

C^

<

o

£-

H

-TS

«o

03

O

1

c»

fa
o

X

1)

C3^

m

^"^

go

H

■s<^

Z

dS

iO,_i,-Hi— ICOOJ COO'— iCD'OiO

<-H 1-H >-l (M C^ C<1

C<1 (N

O

■^00 <-H ►r—'OOCCiiO'-iT-i

t^ -^ §

^ CO

0205coc^Tt<i— I <o ■^^locococo ~

TjHlOlO r^ 1— (C^IOOOOt^CO ^

00 CO O (N C-l C-1 C<) C^l !N C<1 C5 "-I "g

o

o

5; .£„

r") ,2y, (Mt-i,-hi-<i-i c<i'tcoco(M'-t

S " d

x-3

iC lO IC O 'O o c o o o o o

-5"o GC' GC o -* GO CO 1^ t-^ ■'t' re tc ci

^_; 4_ *-. -fJ

*^ -3 rr -C J= ^

v. ~ t, ^ <- -w

1— I 61 re "* i-t O

JULLETIN 318 THE EFFECTS OP ALKALI ON CITRUS TREES 337

y.

OO'^CC'J'C^ i.OOCX'O^

Sif

(M 00 >0 05

o

SC

'-'

y.

u

G

si^

s

_o

Cl,

H

ZZ

B
O

W

li

b

g

U.

<

J-

'/3

«^^

<

-c

2o

2

■3^

X'

(K

o

o

t-,

X

;<

o

u.

o

<^

Co

■x

oH

H

xU

y.

u

o -^

D

»

H

P

CO

Z

c

O

U

Is

X .Si o

0) a> 0) a> 01 « oo
H E-i H H H r-i >^

O)

(M Ol 00 (N O O

»C CO »o t^ m «o

4

?C ■* -^ C<3

OOOOiC'O lOOO'OOO

■M C^-l CO C' 1^ O ^0 O t^ O C: 00

^r o c^ c^i c^ ro lo Tf lit -.c 00 CO

7. G t. <—-.-' <— x C t- ^- -^ -^^

^.^^. (•); :'A,i HORllCULlUUt

209908 ^.j^^j^^^, ^^p AGf^lCULTURE
RPRKEIFY CALIFORNIA

This book is DUE on the last date stamped below

a JUL 23^965

LD

geCTD
MAY 18

UMJRL

Ju/y

Form L-9-15m-7,'32

^WIVBBSITY of CALIFORNT*

A 001095 888