UTILIZATION AND RECLAMATION OF ALKALI LANDS.
_Alkali-Resistant Crops._—The most obvious mode of utilizing alkali
lands is to occupy them with crops not affected by the noxious salts.
Unfortunately but few such crops of general utility have as yet been
found for the stronger class of alkali lands. The question is always
one of degree, which frequently cannot be decided without an actual
determination of the amount and kind of salts to be dealt with, to
which the crops can then be adapted in accordance with the greater
or less sensitiveness of the several plants, as indicated in the
table of tolerances given farther on. But aside from this, there are
certain general measures and precautions which in any case will serve
to mitigate the effect of the alkali salts. Foremost among these, and
applicable everywhere, is the prevention of evaporation to the utmost
extent possible.
_Counteracting Evaporation._—Since evaporation of the soil-moisture
at the surface is what brings the alkali to the level where the
main injury to plants occurs, it is obvious that evaporation should
be prevented as much as possible. This is the more important, as
the saving of soil-moisture, and therefore of irrigation water, is
attainable by the same means.
Three methods for this purpose are usually practiced, viz., shading,
mulching, and the maintenance of loose tilth in the surface soil to
such depth as may be required by the climatic conditions.
As to mulching, it is already well recognized in the alkali regions
of California as an effective remedy in light cases. Fruit trees are
frequently thus protected, particularly while young, after which their
shade alone may (as in the case of low-trained orange trees) suffice
to prevent injury. The same often happens in the case of low-trained
vines, small-fruit, and vegetables. Sanding of the surface to the depth
of several inches was among the first attempts in this direction; but
the necessity of cultivation, involving the renewal of the sand each
season, renders this a costly method. Straw, leaves, and manure have
been more successfully used; but even these, unless employed for the
purpose of fertilization, involve more expense and trouble than the
simple _maintenance of very loose tilth of the surface soil throughout
the dry season_; a remedy which, of course, is equally applicable to
hoed field crops, and is in the case of some of these—_e. g._, cotton—a
necessary condition of cultural success everywhere. The wide prevalence
of “light” soils in the arid regions, from causes inherent in the
climate itself, renders this condition relatively easy of fulfilment.
_Turning-under of Surface Alkali._—Aside, however, from the mere
prevention of surface evaporation, another favorable condition is
realized by this procedure, namely the commingling of the heavily
salt-charged surface-layers with the relatively non-alkaline subsoil.
Since in the arid regions the roots of all plants retire farther
from the surface because of the deadly drought and heat of summer,
it is usually possible to cultivate deeper than could safely be done
with growing crops in humid climates. Yet even there, the maxim of
“deep preparation and shallow cultivation” is put into practice with
advantage, only changing the measurements of depth to correspond with
the altered climatic conditions. Thus while in the humid States, three
to four inches is the accepted standard of depth for summer cultivation
to preserve moisture without injury to the roots, that depth must in
the arid region frequently be doubled in order to be effective; and
will even then scarcely touch a living root in orchards and vineyards,
particularly in unmanured and unirrigated land.
A glance at fig. 63, (chap. 22, p. 431), will show the great advantage
of extra-deep preparation in commingling the alkali salts accumulated
near the surface with the lower soil-layers, diffusing the salts, say
through twelve instead of six inches of soil mass. This will in very
many cases suffice to render the growth of ordinary crops possible if,
by subsequent frequent and thorough cultivation, surface evaporation,
and with it the re-ascent of the salts to the surface, is prevented.
A striking example of the efficiency of this mode of procedure was
observed at the Tulare substation, California, where a portion of a
very bad alkali spot was trenched to the depth of two feet, throwing
the surface soil to the bottom. The spot thus treated produced
excellent wheat crops for two years—the time it took the alkali salts
to reascend to the surface.
It should therefore be kept in mind that whatever else is done toward
reclamation, _deep preparation and thorough cultivation_ must be
regarded as prime factors for the maintenance of production on alkali
lands.
_The Efficacy of Shading_, already referred to, is strikingly
illustrated in the case of some field crops which, when once
established, will thrive on fairly strong alkali soil, provided that
a good thick “stand” has once been obtained. This is notably true
of the great forage crop of the arid region, alfalfa or lucern. Its
seed is extremely sensitive to “black” alkali, and will decay in the
ground unless protected against it by the use of gypsum in sowing. But
when once a full stand has been obtained, the field may endure for
many years without a sign of injury. Here two effects combine, viz.,
the shading, and the evaporation through the deep roots and abundant
foliage, which alone prevents, in a large measure, the ascent of the
moisture and salts to the surface. The case is then precisely parallel
to that of the natural soil (see p. 432, chapter 22), except that, as
irrigation is practiced in order to stimulate production, the sheet of
alkali hardpan will be dissolved and its salts spread through the soil
more evenly. The result is that so soon as the alfalfa is taken off the
ground and the cultivation of other crops is attempted, an altogether
unexpectedly large amount of alkali comes to the surface and greatly
impedes, if it does not altogether prevent, the immediate planting of
other crops. Shallow-rooted annual crops that give but little shade,
like the cereals, while measurably impeding the rise of the salts
during their growth (see fig. 70, page 452) frequently allow of enough
rise after harvest to prevent reseeding the following season.
_“Neutralising” Black Alkali._—Since so little carbonate of soda
as one-tenth of one per cent may suffice to render some soils
uncultivable, it frequently happens that its mere transformation into
the sulfate is sufficient to remove all stress from alkali. Gypsum
(land plaster) is the cheap and effective agent to bring about this
transformation, provided water be also present. The amount required
per acre will, of course, vary with the amount of salts in the soil,
all the way from a few hundred pounds to several tons in the case of
strong alkali spots; but it is not usually necessary to add the entire
quantity at once, provided that sufficient be used to neutralize the
sodic carbonate near the surface, and enough time be allowed for the
action to take place. In very wet soil, and when much gypsum is used,
this may occur within a few days; in merely damp soils in the course of
months; but usually the effect increases for years, as the salts rise
from below.
The effect of gypsum on black-alkali land is often very striking,
even to the eye. The blackish puddles and spots disappear, because
the gypsum renders the dissolved humus insoluble and thus restores it
to the soil. The latter soon loses its hard, puddled condition and
crumbles and bulges into a loose mass, into which water now soaks
freely, bringing up the previously depressed spots to the general level
of the land. On the surface thus changed, seeds now germinate and grow
without hindrance; and as the injury from alkali occurs at or near the
surface, it is usually best to simply harrow in the plaster, leaving
the water to carry it down in solution. Soluble phosphates present
are decomposed so as to retain finely divided, but less soluble earth
phosphates in the soil.
It must not be forgotten that this beneficial change may go backward
if the land thus treated is permitted to be swamped by irrigation
water or otherwise. Under the same conditions naturally white alkali
may turn black (see above, chapter 22, p. 451). Of course, gypsum is
of no benefit whatever on soils containing no “black” alkali, but only
(“white”) Glauber’s and common salt.
_Removing the Salts from the Soil._—In case the amount of salts in
the soil should be so great that even the change worked by gypsum is
insufficient to render it available for useful crops, the only remedy
left is to remove the salts, partially or wholly, at least from the
_surface_ of the land. Three chief methods are available for this
purpose. One is to remove the salts, with more or less earth, from the
surface at the end of the dry season, either by sweeping or by means of
a horse scraper set so as to carry off a certain depth of soil. Thus
sometimes in a single season one-third or one-half of the total salts
may be got rid of, the loss of a few inches of surface soil being of
little moment in the deep soils of the arid region. Another method
affording partial relief is to flood the land for a sufficient length
of time to carry the alkali three or more feet below the surface, then
carefully preventing its re-ascent by suppressing evaporation (see this
chapter, p. 455) as much as possible. The best of all, the final and
universally efficient remedy, is to leach the alkali salt out of the
soil into the country drainage; supplementing by irrigation water what
is left undone by the deficient rainfall.
It is not practicable, as many suppose, to wash the salts off the
surface by a rush of water, as they instantly soak into the ground at
the first touch. Nor is there any certain relief from allowing the
water to stand on the land and then drawing it off; in this case also
the salts soak down ahead of the water, and the water standing on the
surface remains almost unchanged. In very pervious soils and in the
case of white alkali, the washing-out can often be accomplished without
special provision for underdrainage, by leaving the water on the land
sufficiently long. But the laying of regular underdrains greatly
accelerates the work, and renders success certain.
_Leaching-Down._—In advance of underdrainage, it is quite generally
feasible, where the land has been leveled and diked for irrigation by
surface flooding, to leach the salts out of the first three or four
feet by continued flooding, thus taking them out of reach of the crop
roots, or at all events giving the _seed_ an opportunity to escape
injury from alkali. This plan is especially effective in the case of
alfalfa, the young seedlings of which are very sensitive, while the
grown plant is rather resistant. In order to obtain this relief so
as to know what is being accomplished, the farmer should ascertain
beforehand how fast water will soak down in his ground;[174] for in
heavy clay soils, and especially in those containing black alkali,
the soakage is sometimes so slow that the upward diffusion of the
salts keeps pace with the downward soakage; in which case nothing is
accomplished by flooding, and underdrainage is the only remedy. But in
most soils of the arid region flooding from three days to a week will
remove the alkali beyond reach of the roots of ordinary crops. If
subsequently irrigation is done by means of _deep_ furrows, the alkali
salts may be either kept at a low level continuously, or if the land
be at all pervious, the alkali may ultimately be permanently leached
out into the subdrainage by farther flooding. When the alkali has not
accumulated near the surface to any great extent, irrigation by deep
furrows may, alone, afford all the relief needed.
[174] See p. 242, Chap. 13.
[Illustration: FIG. 71.—Lemon Orchard Affected by Alkali; Before Deep
Irrigation.]
In the case illustrated by figures 71 and 72, irrigation by shallow
furrows with water too strongly charged with salts had so far added to
the natural alkali-content of the land that the lemon trees were being
defoliated. Upon the advice of the California Station the deep-furrow
system was adopted, and within two years the results were as shown in
figure 72, the salts having been carried down and diluted so as to
become harmless.
_Underdrainage the Final and Universal Remedy for Alkali._—When we
underdrain an alkali soil, we adopt the very means by which the
existence of alkali lands in the humid regions is wholly prevented;
the leaching-out of the soluble salts formed in soil-weathering as
fast as they are formed. The long and abundant experience had with
underdrainage in reclaiming saline sea-coast lands, applies directly
and cogently to alkali lands. It is the universal remedy for all the
evils of alkali, and its only drawback is the first expense, and the
necessity for obtaining an outlet for the drain waters, which cannot
always be had on the owner’s land. Hence it requires co-operation or
legislation to render the great improvement of underdrainage feasible.
Such legislation is well established in the old world, and has been
enacted in several states even of the humid region. Where irrigation
is practiced as a matter of necessity, underdrainage is a correlative
necessity, both to avoid the evils of over-irrigation and to relieve
the land of noxious alkali salts.
[Illustration: FIG. 72.—The Above Orchard after Alkali was Driven Down
by Deep Irrigation, followed by Cultivation.]
The drainage law now existing in California does not go farther than
to authorize the formation of drainage districts, within which the
necessary taxes may be levied; and there is some difficulty in securing
popular action. But bitter experience will doubtless in time compel
unanimity, such as now exists, _e. g._, in Illinois, where drainage is
not nearly so urgently needed as it is in the irrigation states.
_Possible Injury to Land by Excessive Leaching._—It should not be
forgotten, however, that excessive leaching of underdrained land by
flooding is liable to injure the soil in two ways: first, by the
removal of valuable soluble plant-food; and further, by rendering the
land less retentive of moisture, such retention being favored by the
presence of small amounts of alkali salts, not sufficient to injure
crops. After the salts have been carried down to a sufficient depth to
prevent injury to annual crops, and with proper subsequent attention
to the prevention of surface evaporation, the flooding will not need
to be repeated for several years. Thus in many soils excellent crops
may be grown even in strong alkali land, pending the establishment of
permanent drainage systems.
The importance of thoroughly washing the alkali deeply
into the soil before the seed is planted, and keeping it
there by proper means until the foliage of the plant shades
the soil sufficiently to prevent the rise of moisture and
alkali, is well illustrated in fields in the region of
Bakersfield, Cal., where alfalfa is now growing in soils
once heavily charged with alkali.[175] From one of these fields
samples of soil were taken where the alkali was supposed
to be strongest beneath the alfalfa, and also from an
adjoining untreated alkali spot, which was said to represent
conditions before alfalfa was planted. The results are given
in pounds per acre in four feet depth.
===========================+========+==========+=========+========
|Sulfate.|Carbonate.| Common | Total
| | | Salt. | Alkali.
---------------------------+--------+----------+---------+--------
Alkali spot before alfalfa | | | |
was planted | 60,120 | 720 | 175,840 | 236,680
| | | |
Alfalfa field; alkali | | | |
washed down | 14,400 | | 1,040 | 18,640
---------------------------+--------+----------+---------+--------
Here the surface foot of the natural soil contained nearly
140,000 pounds of common salt, a prohibitory amount. Similar
experience has been had near Yuma, Arizona.
[175] Bull. 133, Cal. Expt. Sta., by R. H. Loughridge.
_Difficulty in Draining “Black” Alkali Lands._—An important exception
to the efficacy of draining, however, occurs in the case of black
alkali in most lands. In this case either the impervious hardpan or
(in the case of actual alkali spots) the impenetrability of the surface
soil itself will render even underdrains ineffective unless the salsoda
and its effects on the soil are first destroyed by the use of gypsum,
as above detailed. This is not only necessary in order to render
drainage and leaching possible, but is also advisable in order to
prevent the leaching-out of the valuable humus and soluble phosphates,
which are rendered insoluble (but not unavailable to plants) by the
action of the gypsum. Wherever black alkali is found in lands not very
sandy, the application of gypsum should precede any other efforts
toward reclamation. Trees and vines already planted may be temporarily
protected from the worst effects of the black alkali by surrounding the
trunks with gypsum or with earth abundantly mixed with it. Seeds may be
similarly protected in sowing, and young plants in planting.
_Swamping of Alkali Lands._—It should, however, be remembered that the
_swamping_ of alkali lands, whether of the white or black kind, is
fatal not only to their present productiveness, but also, on account
of the strong chemical action thus induced, greatly jeopardizes their
future usefulness. Many costly investments in orchards and vineyards
have thus been rendered unproductive, or have even become a total loss.
_Reduction of Alkali by Cropping._—Another method for diminishing the
amount of alkali in the soil is the cropping with plants that take
up considerable amounts of salts. In taking them into cultivation,
it is advisable to remove entirely from the land the salt growth
that may naturally cover it, notably the greasewoods (_Sarcobatus_,
_Allenrolfea_), with their heavy percentage of alkaline ash (12 to 20
per cent). Crop plants adapted to the same object are mentioned farther
on. Such crops should also, of course, be wholly removed from the land.
_Total Amounts of Salts Compatible with Ordinary Crops; Tolerance of
Culture Plants._—Since the amount of alkali that reaches the surface
layer is largely dependent upon the varying conditions of rainfall or
irrigation, and surface evaporation, it is difficult to foresee to
what extent that accumulation may go, unless we know the total amount
of salts present that may be called into action. This, as already
explained, can ordinarily be ascertained by the examination of one
sample representing the average of a soil column of four feet. By
calculating the figures so obtained to an acre of ground, we can at
least approximate the limits within or beyond which crops will succeed
or perish. Applying this procedure to the cases represented in the
diagrams (pp. 434, 452, chapter 22) and estimating the weight of the
soil per acre-foot at 4,000,000 pounds, we find in the land on which
barley refused to grow the figures 32,470 and 43,660 pounds of total
salts per acre, respectively corresponding to 0.203 per cent for the
first figure (the second, representing only the two surface feet, is
not strictly comparable). For the land on which barley gave a full
crop, we find for the May sample 25,550 pounds, equivalent to 0.159 per
cent for the whole soil column of four feet. It thus appears that for
barley the limits of tolerance lie between the above two figures. It
should be noted that in this case a full crop of barley was grown even
when the alkali consisted of fully one-half of the noxious carbonate
of soda; proving that it is not necessary in every case to neutralize
the entire amount of that salt by means of gypsum, which in the present
case would have required about 9½ tons of gypsum per acre—a prohibitory
expenditure.
_Relative Injuriousness of the Several Salts._—Of the three sodium
salts that usually constitute the bulk of “alkali,” only the carbonate
of soda is susceptible of being materially changed by any agent that
can practically be applied to land. So far as we know, the salt of
sodium least injurious to ordinary vegetation is the sulfate, commonly
called Glauber’s salt, which ordinarily forms the chief ingredient of
“white” alkali. Thus barley is capable of resisting about five times
more of the sulfate than of the carbonate, and quite twice as much as
of common salt. Since the maximum percentage that can be resisted by
plants varies materially with the kind of soil, it is difficult to give
exact figures save with respect to particular cases. For the sandy loam
of the Tulare substation, California, for instance, the maximum for
cereals may be approximately stated to be one-tenth of 1 per cent for
salsoda; a fourth of 1 per cent for common salt; and from forty-five
to fifty one-hundredths of one per cent of Glauber’s salt. For clay
soils the tolerance is in general markedly less, especially as regards
the salsoda; since in their case the injurious effect on the tilling
qualities of the soil, already referred to, is superadded to the
corrosive action of that salt upon the plant.
[Illustration: FIG. 73.—Alkali curve showing percentage of Alkali Salts
in field of Sugar Beets, Oxnard, Calif.]
[Illustration: FIG. 74.—Beets from corresponding positions in the above
field.]
_Effect of Differences in Composition of Alkali Salts on
Beets._—The marked differences which may occur as the
result of even slight variations in the proportions of the
several salts is well illustrated in the subjoined diagram
of observations made by Dr. G. W. Shaw, of the Cal. Expt.
station, upon beet fields in the neighborhood of Oxnard,
Cal. The lands lie not far from the seashore, and saline
water underruns them for considerable distance inland.
The soil and subsoil are quite sandy, so that it takes
irrigation water only about seven hours to penetrate from the
surface to bottom water at seven feet depth. The land on
which these observations were made are apparently level to
the eye, though probably the alkali belts on which the sugar
beets were “poor” are slightly depressed swales.
It will be noted that here the beets were “good” where the sulfate
(Glauber’s salt) ranged up to .8%, with .10 to .20 of common salt; but
that so soon as the latter rose above .20, the beets were poor despite
the low percentage of Glauber’s salt; then became “good” again so
soon as the common salt fell below .20%, although the Glauber’s salt
increased.
TOLERANCE OF VARIOUS CROP PLANTS.
The following table, compiled by Dr. R. H. Loughridge mainly from his
own observations,[176] gives the details of the tolerance for various
culture plants as ascertained at the several experiment substations in
California, as well as at other points in that State and in Arizona
where critical cases could be found. It is thought preferable to
investigate analytically such cases in the field, rather than to
attempt to obtain results from small-scale experiments artificially
arranged, in which sources of error arising from evaporation and other
causes are most difficult to avoid.
[176] Bulletins Nos. 128, 133 and 140, Calif. Expt. Station.
The table is so arranged as to show the maximum tolerance
thus far observed for each of the three single ingredients,
as well as the maximum of total salts found compatible with
good growth. In view of the extremely variable proportions
between the three chief ingredients found in nature, this
seems to be the only manner in which the observations made
can be intelligibly presented, until perhaps a great number
of such data shall enable us to evolve mathematical formulæ
expressing the tolerance for the possible mixtures for
each plant. For it is certain that the tolerance-figures
will be quite different in presence of other salts, from
those that would be obtained for each salt separately; or
for the calculated mean of such separate determinations,
proportionally pro-rated. It must also be remembered that in
all alkali soils, lime carbonate is abundantly present, as
is, nearly always, a greater or less amount of the sulfate
(gypsum). As already stated, according to the investigations
of Cameron not only these compounds, but also calcium
chlorid, exert a protective influence against the injury to
plant growth from compounds of sodium and potassium. The
figures here given can therefore be regarded only as
approximations, subject to correction by farther observation.
They are arranged from the highest tolerances downward, for
each of the three ingredients, as well as for the totals. The
latter are not, of course, the sums of the figures given in
the preceding columns, but independent data.
HIGHEST AMOUNT OF ALKALI IN WHICH FRUIT TREES
WERE FOUND UNAFFECTED.[177]
Arranged from highest to lowest. Pounds per acre in four feet depth.
=================+===============+================+=================
Sulfates | Carbonate | Chlorid | Total Alkali.
(Glauber’s Salt).| (Salsoda). | (Common Salt).|
-----------------+---------------+----------------+-----------------
Grapes 40,800| Grapes 7,550| Grapes 9,640| Grapes 45,700
Olives 30,640| Oranges 3,840| Olives 6,640| Olives 40,160
Figs 24,480| Olives 2,880| Oranges 3,360| Almonds 25,560
Almonds 22,720| Pears 1,760| Almonds 2,400| Figs 26,400
Oranges 18,600| Almonds 1,440| Mulberry 2,240| Oranges 21,840
Pears 17,800| Prunes 1,360| Pears 1,360| Pears 20,920
Apples 14,240| Figs 1,120| Apples 1,240| Apples 16,120
Peaches 9,600| Peaches 680| Prunes 1,200| Prunes 11,800
Prunes 9,240| Apples 640| Peaches 1,000| Peaches 11,280
Apricots 8,640| Apricots 480| Apricots 960| Apricots 10,080
Lemons 4,480| Lemons 480| Lemons 800| Lemons 5,760
Mulberry 3,360| Mulberry 160| Figs 800| Mulberry 5,760
-----------------+---------------+----------------+-----------------
[177] The several columns of figures are independent of each other; the
“total” alkali is not the summation for the three salts in the same
line.
OTHER TREES.
---------------------+-------------------+--------------------
Kölreuteria 51,040| Kölreuteria 9,920| Or. Sycamore 20,320
Eucal. am. 34,720| Or. Sycamore 3,200| Kölreuteria 12,640
Or. Sycamore 19,240| Date Palm. 2,800| Eucal. am. 2,960
Wash. Palm 13,040| Eucal. am. 2,720| Camph. Tree 1,420
Date Palm 5,500| Wash. Palm 1,200| Wash. Palm 1,040
Camph. Tree 5,280| Camph. Tree 320|
---------------------+-------------------+--------------------
Kölreuteria 73,600
Or. Sycamore. 42,760
Eucal. am. 40,400
Wash. Palm 15,200
Date Palm 8,328
Camph. Tree 7,020
---------------------
SMALL CULTURES.
---------------------+-------------------+---------------------
Saltbush 125,640| Saltbush 18,560| Modiola 40,860
Alfalfa, old 102,480| Barley 12,170| Saltbush 12,520
Alfalfa, young 11,120| Bur Clover 11,300| Sorghum 9,680
Hairy Vetch 63,720| Sorghum 9,840| Celery 9,600
Sorghum 61,840| Radish 8,720| Onions 5,810
Sugar Beet 52,640| Modiola 4,760| Potatoes 5,810
Sunflower 52,640| Sugar Beet 4,000| Sunflower 5,440
Radish 51,880| Gluten Wheat 3,000| Sugar Beet[178] 10,240
Artichoke 38,720| Artichoke 2,760| Barley 5,100
Carrot 24,880| Lupin 2,720| Hairy Vetch 3,160
Gluten Wheat 20,960| Hairy Vetch 2,480| Lupin 3,040
Wheat 15,120| Alfalfa 2,360| Carrot 2,360
Barley 12,020| Grasses 2,300| Radish 2,240
Goat’s Rue 10,880| Kaffir Corn 1,800| Rye 1,720
Rye 9,800| Sweet Corn 1,800| Artichoke 1,480
Cañaigre 9,160| Sunflower 1,760| Gluten Wheat 1,480
Ray Grass 6,920| Wheat 1,480| Wheat 1,160
Modiola 6,800| Carrot 1,240| Grasses 1,000
Bur Clover 5,700| Rye 960| White Melilot 440
Lupin 5,440| Goat’s Rue 760| Goat’s Rue 160
White Melilot 4,920| White Melilot 480| Cañaigre 80
Celery 4,080| Cañaigre 120|
Saltgrass 44,000| Saltgrass 136,270| Saltgrass 70,360
----------------------+-------------------+---------------------
Saltbush 156,720
Alfalfa, old 110,320
Alfalfa, young 13,120
Sorghum 81,360
Hairy Vetch 69,360
Radish 62,840
Sunflower 59,840
Sugar Beet 59,840
Modiola 52,420
Artichoke 42,960
Carrot 28,480
Barley 25,520
Gluten Wheat 24,320
Wheat 17,280
Bur Clover 17,000
Celery 13,680
Rye 12,480
Goat’s Rue 11,800
Lupin 11,200
Cañaigre 9,360
Onions 38,480
Potatoes 38,480
Saltgrass 381,110
----------------------
[178] Figures taken from Bulletin 169, Calif. Expt. Station, June,
1905.
_Comments on the Above Table._—Considering in this table, first, the
plants suitable for the stronger class of alkali lands, it may be
said generally that the search for widely acceptable kinds has not
been very successful. It is true that cattle will nibble green salt
grass (_Distichlis spicata_), but will soon leave it for any dry
feed that may be within reach. The enormous amount of salts which
it will tolerate in the soil on which it grows, and the doubtless
correspondingly large amount of those salts which it will absorb,
judging from its taste, sufficiently explain the reluctance of cattle
to feed on it to any considerable extent.
The same is true of all the fleshy plants that grow on the stronger
alkali lands, and are known under the general designation of “alkali
weeds.” When stock unaccustomed to it are forced by hunger to feed on
such vegetation to any considerable extent, disordered digestion is
apt to result; which in such ranges, however, is often counteracted by
feeding on aromatic or astringent antidotes, such as the gray sagebrush
and the more or less resinous herbage of plants of the sunflower family.
In the Great Basin region, lying between the Sierra Nevada and the
front range of the Rocky Mountains, there are, aside from the grasses,
numerous herbaceous and shrubby plants that afford valuable pasturage
for stock,[179] and some of these grow on moderately strong alkali
land; the same is true in California. It is quite possible that some of
these will be found to lend themselves to ready propagation for culture
purposes as well as they do for restocking the ranges. But thus far
none have found wider acceptance, probably because their stiff branches
and upright habit render them inconvenient to handle. It will require
more extended experience and experiment before any of these will be
definitely adopted for propagation by farmers and stockmen.
[179] See Bulletin No. 16 of the Wyoming Experiment Station; also
Bulletin Nos, 2 and 12 of the Division of Agrostology, and Farmers’
Bulletin No. 108, U. S. Department of Agriculture.
_Saltbushes, and Herbaceous Crops._
_Australian Saltbushes._—Experience in California indicates that in the
more southerly portion of the arid region, unpalatable native plants
may be largely replaced, even on the ranges, by one or more species
of the Australian saltbushes (_Atriplex spp._), long ago recommended
by Baron von Mueller of Melbourne; of which one (_A. semibaccata_)
has proved eminently adapted to the climate and soil of California
and is readily eaten by all kinds of stock. The facility with which
it is propagated, its quick development, the large amount of feed
yielded on a given area, even on the strongest alkali land ordinarily
found, and its thin, flexible stems, permitting it to be handled very
much like alfalfa, seem to commend it especially to the farmers’
consideration wherever better forage plants cannot be grown and the
climate will permit of its use. It does not, however, resist the severe
cold of the interior plateau country, and is wholly out of place in
the Pacific Coast region where summer fogs prevail. Most of the other
Australian species have an upright, shrubby habit, which adapts them
better to browsing than to pasture proper. The same is true of the
Argentine species (_A. Cachiyuyum_), which in its native pampas is
highly esteemed for that purpose, and succeeds well in California.
Of other Australian saltbushes, _A. halimoides_, _vesicaria_ and
_leptocarpa_ are the most promising; the latter is somewhat similar in
habit to the semibaccata, but is not as vigorous a grower. Since some
of the saltbushes take up nearly one fifth of their dry weight of ash
ingredients,[180] largely common salt, the complete removal from the
land of a five-ton crop of saltbush hay will take away nearly a ton of
the alkali salts per acre. This will in the course of some years be
quite sufficient to reduce materially the saline contents of the land,
and will frequently render possible the culture of ordinary crops.
[180] Analyses made at the California station show 19.37 percent of ash
in the air-dry matter of Australian saltbush. (See California Station
Bulletin No. 105; E. S. R., vol. 6, p. 718). Analyses of Russian
thistle have been reported showing over 20 per cent of ash in dry
matter. (See Minnesota Sta. Bulletin No. 34; Iowa Sta. Bull. No. 26; E.
S. R., vol. 6, pp. 552-553).
_Modiola._—Alongside of the saltbushes, the Chilean plant _Modiola
procumbens_, now generally known as modiola simply, deserves attention,
as it makes acceptable pasture where alfalfa fails to make a stand on
account of alkali. It is a trailing plant with medium-sized, roundish
foliage, and roots freely at the joints where they touch the ground.
Unlike the saltbushes it is therefore a formidable weed where it is not
wanted; but as according to California experience it resists as much as
52,000 pounds of salts per acre, even when 41,000 of these is common
salt, it is likely to be useful in many cases, particularly as an
admixture to a saltbush diet for stock, as it does not absorb as much
salt as the latter. It seems best adapted to pasturage.
As the table shows that, once grown to the age of a few years, alfalfa
will resist a percentage of alkali next to the saltbush, it will
generally be worth while, in lands otherwise adapted to alfalfa, to
prepare the land by leaching-down (see above) so as to secure a stand
of the more valuable crop.
_Native Grasses._[181]—Of all known plants that stock will eat somewhat
freely, the tussock grass (_Sporobolus airoides_, of which a figure
is given farther on), a native of the southern arid region, endures
the largest amounts of alkali; having been found growing well on land
containing the enormous amount of nearly half a million pounds of salts
per acre, although it will thrive with only 49,000 pounds in the soil.
What it will do under cultivation has never been fairly tested; but
its bare tussocks, killed by the excessive browsing of stock, testify
to its acceptableness as forage. It does not seem to absorb excessive
amounts of salts.
[181] It should be understood that the plants so referred to are
exclusively the _true_ grasses, recognized as such by every child,
and not forage plants generally; which are sometimes so designated;
not only by farmers, but by some authors who fail to appreciate the
practical importance of the distinction, which makes it necessary that
farmers should be taught to understand it.
Aside from the alkali grass proper (_Distichlis_), mentioned above,
the so-called rye grass of the Northwest (_Elymus condensatus_) is
probably, next to the tussock grass, the most resistant species among
the wild grasses. Its southern form, with several others not positively
identified, occupies largely the milder alkali lands of southern
California. This grass, though rather coarse, is regularly cut for hay
in the low grounds of Oregon and Washington.
Doubtless some of the indigenous grasses of the interior plateau
region and of the great plains east of the Rocky Mountains, such as
the buffalo and grama grasses, as well as several of the wheat grasses
(_Agropyron_) and bunch grasses (_Festuca_, _Poa_, _Stipa_, etc.) will
prove resistant to larger proportions of alkali than the meadow and
pasture grasses of the regions of summer rains.
_Cultivated Grasses._—The superficial rooting and fine fibrous roots
of the true annual grasses render them, as a whole, rather sensitive
to alkali; yet the cereals—barley, wheat, rye and oats—resist, as the
table shows, the average alkali salts to the extent of from 17,000
total salts, with not exceeding 1500 pounds of carbonate, in the case
of the more delicate varieties of wheat, to over 25,000 pounds per acre
in the case of barley, which with the gluten wheats and rye seems to
have the highest tolerance-figure. The special adaptation of gluten
wheats to arid conditions is thus emphasized. The roots of these
cereals are comparatively stout, with thick epidermis.
Among the cultivated forage grasses proper, the Australian variety of
the English ray (generally miscalled rye) grass seems most resistant.
The eastern fescues, Kentucky blue grass, and others at home in the
humid region are easily injured, as those who try to maintain lawns
on alkali-tainted lands, or by irrigation with alkali waters, know
to their sorrow. To these grasses common salt and bittern (magnesium
chlorid) seem to be particularly injurious, and they tolerate but
little “black alkali.”
On the rather close-textured soil at Chino, California, the loliums,
including the darnel (“California cheat”), and the Australian and
Italian ray (“rye”) grasses, succeed fairly on land containing as much
as 6,000 pounds of (white) salts. Most other cultivated grasses failed
conspicuously alongside of these. It must be remembered that in more
loose-textured, sandy lands than those in which these tests were made,
the above figures for tolerance would probably be increased by 30
percent or more.
_Maize_ is rather sensitive to alkali, and suffers even on slightly
alkaline land, owing doubtless to the large development of fine
white rootlets near the surface, so familiar to corn-growers. The
_Sorghums_, and especially Egyptian corn (durra) are much less
sensitive, as the table shows, and are among the first crops to be
tried on alkali lands. The related millets share this resistance more
or less, and we often see on cultivated lands in the alkali region fine
stands of barnyard grass (_Panicum crusgalli_) of which the variety (?)
_P. muticum_ is said by observers of the U. S. Dept. of Agriculture
to be specially resistant, and acceptable to stock. One of the most
successful grasses on the light alkali lands near Chino, where most
of the commonly cultivated grasses fail, was a near relative of the
barnyard grass, the _Eleusine coracana_, which produces heavy crops
of a millet-like grain much relished by poultry, and also by stock.
This grass, largely grown in Egypt, has succeeded well all over the
ground whose alkali content ranges up to 12,000 pounds per acre, but
failed where the salts reached 38,840 pounds in the surface foot.
Next to this, in point of success, were the pearl millet (_Pennisetum
typhoideum_) and teosinte, Hungarian brome grass, and Japanese millet,
on land containing about 9,000 pounds of (chiefly “white”) salts per
acre.
_Other Herbaceous Crops. Legumes._—Both the natural growth of alkali
lands and experimental tests seem to show that this entire family
(peas, beans, clovers, etc.) are among the more sensitive and least
available wherever black alkali exists; while fairly tolerant of the
white (neutral) salts. Apparently a very little salsoda suffices to
destroy the tubercle-forming organisms that are so important a medium
of nitrogen-nutrition in these plants. Excepting the melilots, alfalfa
with its hard, stout and long taproot, seems to resist best of all
these plants.
As a general thing, taprooted plants, when once established,
resist best, for the obvious reason that the main mass of
their feeding roots reaches below the danger level. Another
favoring condition, already alluded to, is heavy foliage and
consequent shading of the ground; alfalfa happens to combine
both of these advantages. There has been some difficulty
in obtaining a full stand of alfalfa in the portion of the
Chino substation tract containing from 4000 to 6000 pounds
of (largely black) alkali salts per acre; but once obtained,
it has done very well.
The only other plant of this family that succeeds well on this land,
and even (at Tulare) on soil considerably stronger (probably between
20,000 and 30,000 pounds) are the two melilots, _M. indica_, and
_alba_; the latter (the Bokhara clover) is a forage plant of no mean
value in moist climates, but somewhat restricted in its use in the
arid region because of the very high aroma it develops, especially
in alkali lands; so that stock will eat only limited amounts, best
when intermixed with other forage, such as the saltbushes. The yellow
melilot is highly recommended by the Arizona Experiment Station as
a green-manure plant for winter growth; but farther north it is a
summer-growing plant only, and is refused by stock. As already stated,
very few plants belonging to this family are naturally found on alkali
lands, and attempts to grow them, even where only Glauber’s salt is
present, have been but very moderately successful.
For most of the legumes the limit of full success seems to lie between
3000 and 4000 pounds to the acre. A marked exception, however, occurs
in the case of the hairy vetch, as shown in the table, where it is
credited, on the basis of repeated experiments, with a tolerance of
nearly 70,000 pounds. This amount was attained, however, in rather
sandy soils. Probably some of the Algerian vetches will likewise prove
more resistant than those which are natives of humid climates.
_Mustard Family._—As in the case of the legumes, wild plants of the
_mustard_ family are rare on alkali lands; and correspondingly, the
cultivated mustard, kale, rape, etc., fail even on land quite weak
in alkali. Their limit of tolerance seems to lie near 4,000 to 5,000
pounds per acre even of white salts. Hence turnips and radishes do not
flourish on alkali lands.
_Sunflower Family._—Several of the hardiest of the native “alkali
weeds” belong to the _sunflower_ family, and the common wild sunflowers
(_Helianthus californicus_ and _H. annuus_) are common on lands
pretty strongly alkaline. The cultivated Russian sunflower, as the
table shows, resists the effects of nearly 60,000 pounds of total
alkali, of which 52,640 pounds was sulfate (Glauber’s salt), and 5440
common salt. This, it will be seen, is a very high tolerance, so
that this sunflower, yielding such excellent poultry feed, is very
widely available. Correspondingly, the “Jerusalem artichoke,” itself
a sunflower, is among the available crops on moderately strong alkali
soils; and so, doubtless, are other members of the same relationship
not yet tested, such as the true artichoke, salsify, etc. Chicory,
belonging to the same family, yielded roots at the rate of twelve tons
per acre, on land of the Chino tract containing about 8,000 pounds of
salts per acre.
_Root Crops._—It seems to be generally true that root crops suffer in
quality, however satisfactory may be the quantity, harvested on lands
rich in salts, and especially in chlorids (common salt). It was noted
at the Tulare substation (California) that the tubers of the artichoke
were inclined to be “squashy” in the stronger alkali land, and failed
to keep well; the same was true of potatoes, which were very watery;
and also of turnips and carrots. It is a fact well known in Europe,
that potatoes manured with kainit (chlorids of potassium and sodium)
are unfit for the manufacture of starch, and are generally of inferior
quality. But this is found not to be the case when, instead of the
chlorids, the sulfate is used; hence the advice, often repeated by the
California station, that farmers desiring to use potash fertilizers
should call for the “high-grade sulfate” instead of the cheaper
kainit, which adds to the injurious salts already so commonly present
in lowland soils of the arid region. Such root crops are, however,
available for stock feed.
The common _beet_ (including the mangel-wurzel) is known to succeed
well on saline seashore lands, and it maintains its reputation on
alkali lands also. Being especially tolerant of common salt, it may
be grown where other crops fail on this account; but the roots so
grown are strongly charged with common salt, and have, as is well
known, been used for the purpose of removing excess of the same from
sea-coast-marsh lands. Such roots are wholly unfit for sugar-making.
It is quite otherwise with Glauber’s salt (sodium sulfate); and as
this is very commonly predominant in alkali lands, either before or
after the gypsum treatment, this fact is of great importance, for it
frequently permits of the successful growing of the sugar beet; as
has been abundantly proved at the Chino ranch, where land containing
as much as 60,000 pounds of salts, mostly this compound, has yielded
roots of very high grade, both as to sugar percentage and purity. But
the analyses of the Oxnard soil show that more than 10,000 pounds of
common salt will be required to render sugar beets unsatisfactory for
sugar-making.
Passing to _stem crops_, we find that _asparagus_, originally itself a
denizen of the sea-board, resists considerable amounts (not yet exactly
determined) of common salt as well as of Glauber’s salt. It is even
claimed that when grown with a dressing of common salt the asparagus is
more tender and savory. But it is quite sensitive to “black alkali,”
which must be neutralized with gypsum to render it harmless.
_Celery_ did well with 13,640 pounds, of which nearly 10,000 was common
salt. But with 30,000 pounds the plants were killed.
_Rhubarb_ was a conspicuous failure, even in the weak and mostly
“white” alkali lands of the Chino station tract.
_Textile Plants._—_Japanese hemp_, while young, seemed to have a
hard struggle with the alkali, but at the end of the season stood
eight feet high. The _ramie_ plant, also, will bear moderately strong
alkali, apparently somewhat over 12,000 pounds per acre. _Flax_ has
not been tested in cultivation; but the wide distribution of wild flax
all over the arid portions of the States of Oregon and Washington,
would seem to indicate that it is not very sensitive. Another textile
plant, the Indian mallow (_Abutilon avicennae_), was found to fail
on the Chino alkali soil. But its close relative, cotton, does not
seem to be specially sensitive, according to the experience had with
it in the Merced river bottom in California; and its culture is
extensive in Egypt, where no particular care seems to be exercised in
selecting the land for the crop. It is just possible that the saline
content of the soil has in California, as well as in the Atlantic
sea-islands, contributed to the superior length of the fiber shown in
the measurements made during the Census work of 1880.[182]
[182] Report on Cotton Culture; 10th Census of the United States, vol.
5, pp. 23 to 34.
_Tolerance of Shrubs and Trees._
_Grapevines._—The European grape, _Vitis vinifera_, is quite tolerant
of white or neutral alkali salts, and will resist even a moderate
amount of the black so long as no hardpan is allowed to form. At
the Tulare substation it was found that grapevines did well in sandy
land containing 35,230 pounds of alkali salts, of which one half was
Glauber’s salt, 9,640 pounds carbonate of soda, 7,550 pounds of common
salt, and 750 pounds nitrate of soda. They were badly distressed
where, of a total of 37,020 pounds of alkali salts, 25,620 pounds
was carbonate of soda; while where the vines had died out, there was
found a total of 73,930 pounds, with 37,280 pounds of carbonate. The
European vine, then, is considerably more resistant of alkali even in
its worst (black) form, than barley and rye, at least on sandy land;
and it seems likely that the native grapevines of the Pacific coast,
_californica_, and _arizonica_, would resist even better; a point still
under experiment.
Experience, however, has shown that vines rapidly succumb when by
excessive irrigation the bottom water is allowed to rise, increasing
the amount of alkali salts near the surface, and shallowing the soil
at their disposal. Such over-irrigation has been a fruitful cause
of injury to vineyards in the Fresno region, and would doubtless if
practiced kill most of the vines at the Tulare substation, which are
now flourishing. In such cases, sometimes the formation of hardpan is
followed by that of a concentrated alkaline solution above it, strong
enough to corrode the roots themselves, and not only killing the vines,
but rendering the land unfit for any agricultural use whatsoever. The
swamping of alkali lands, whether of the white or black kind, is not
only fatal to their present productiveness, but, on account of the
strong chemical action thus induced, greatly jeopardizes their future
usefulness. Many costly investments in orchards and vineyards have thus
been rendered unproductive, or have even become a total loss.
It should be remembered in this connection that as the roots of vines
will, when unobstructed, go to depths of fifteen and even twenty feet,
a subsequent rise of the bottom water from leaky irrigation ditches
will drown out the ends of the deep roots and thus cause the whole root
system to become diseased, inevitably resulting in unproductiveness, if
not death, of the vine.
_Citrus Trees._—Although the high figure of nearly 27,000 pounds for
the tolerance of citrus trees, as given in the table, seems to place
them rather high on the list, such high tolerance actually occurs
only in very sandy soils, and when common salt is in small proportion.
Generally speaking, the citrus tribe are rather sensitive to alkali
salts, and more especially to common salt. In fact, as to the high
tolerance-figure given in the table, observed in sandy land, the
alkali there contained only a trace of common salt. Young seedling
trees are particularly sensitive; so that it is often difficult to
obtain a stand even when, later on, the feeding roots descend beyond
the reach of injury. In the close-textured lands of Chino, young trees
hardly maintained life with more than 5,000 pounds of total salts.
Near Riverside, full-grown trees perished under the influence of
bottom water containing 0.25%, or 146 grains of salt per gallon, which
impregnated the ground; corresponding to about 9,000 pounds per acre in
four feet.
In the sandy loam lands near Corona, trees eight years old suffered
severely when by irrigation with alkali-water the alkali-content of
the land reached 11,000 pounds per acre; as illustrated in Figs. Nos.
44, and 45. At another point in the same region, two representative
trees were selected for comparison, five rows apart on land absolutely
identical; one of these retained its leaves, though suffering, the
other was completely leafless. The leaching of the alkali to the depth
of four feet gave the following results, calculated to pounds per acre:
Sulfates. Carbonates. Chlorids. Total.
Poor tree 4,720 1,680 2,520 8,920
Better tree 4,120 2,360 720 7,200
Here it is apparently the excess of common salt to which the difference
is due, and this despite the higher content of carbonate of soda in the
soil bearing the better tree.
On the other hand, at the Tulare substation orange trees (sour stock)
maintain vigorous growth and good bearing in a very sandy tract which
to the depth of seven feet showed an aggregate content of 26,840 pounds
of salts (or 22,780 to four feet depth); but which is never irrigated.
(See diagram No. 66). The salts in this case consists wholly of sulfate
and carbonate of soda in the ratio of fifty-four to forty-two, implying
the presence of nearly 12,000 pounds of salsoda within reach of the
tree roots; yet in the absence of common salt, no perceptible injury or
even stress upon the trees has been noted.
According to observations made in San Diego county, Calif., lemon trees
are even more sensitive to common salt than oranges, since a total
content of 8,000 pounds per acre, about one-third of which was common
salt, seemed to render the trees wholly unprofitable.
In view of these facts, showing that common salt is the portion of
alkali by far most injurious to citrus trees, great care should be
taken in the use of irrigation waters to exclude those charged with
that compound; and also to avoid locating citrus orchards on land
already impregnated with common salt.
The _olive_ tree, as the table shows, is among the most resistant to
alkali salts, approaching the grape in this respect. This might have
been anticipated from its extended culture in the arid regions of the
old world, including Palestine and northern Africa, where alkali lands
abound. It is probable that the figure given in the table does not yet
show the extreme limit of its endurance.
California experience with the _date palm_, as the table shows, credits
it with an endurance not exceeding 8320 pounds of total salts. This is
doubtless an underestimate, for in the Sahara desert and Egypt it is
credited with being the culture which will succeed in stronger alkali
than any other cultural plant; and, according to Mr. Means of the
United States Department of Agriculture, it is sometimes irrigated with
water containing as much as 200 grains of salts per gallon. It should
be remembered, however, that these trees always grow in very sandy
lands; and in the desert regions it is often grown below the surface
of the ground, so as to render it wholly independent of the alkali
accumulations on the surface. The extreme limit of its endurance must
therefore remain in doubt until more extended experiments have made
more definite data available.
_Deciduous Orchard Trees._
Among deciduous orchard trees, strangely enough, the _almond_ stands
alongside of the fig in alkali-resistance, as indicated in the table.
The _peach_ seems to be much more sensitive, ranking near the _apricot_
and _prune_, whose tolerance is less than half as high. That the
_pear_ and _apple_, generally counted among the more northern fruits
in the humid region, should excel these stone fruits in endurance of
alkali, is rather unexpected; and the figures concerning the whole
group of these rosaceous fruits admonish us that it is unsafe to
predict, without trial, what may be the outcome of culture tests. Thus
plum trees, apparently in good condition, sometimes suddenly begin to
fail when starting to bear; the fruit appears normal on the outside
for a time, but the pit fails to form, being at times flattened out
like a piece of pasteboard; and the fruit does not mature. Yet there
is no observable injury to the base of the trunk, or to the roots. On
the other hand, pears do well even when the outside bark around the
root-crown is blackened by the action of the alkali salts. But 38,000
pounds, even of sulfate, proves too much for the pear.
The _quince_ appears to be materially more resistant than the apple or
pear. It probably ranges alongside of the fig, the soil-adaptations of
which it shares in other respects also.
The _English walnut_ resents even a slight taint of _black_ alkali;
but is fairly tolerant of “white” salts, as is shown in the peculiarly
suitable light loam soils on the lower Santa Clara river, in Ventura
county, as well as in Orange county, California.
Close figures for the limits of alkali tolerance in the case of
deciduous orchard trees cannot easily be given or determined, owing to
the difficulties inherent in the differences of root penetration in the
several soils and localities; as well as the fact already alluded to,
that in close-textured soils the tolerance is in general decidedly less
than in sandy lands. Hence the figures in the table must be taken as
more nearly representing _relative_ tolerances, rather than absolute
data to be applied in every case. As regards the stone fruits, it
should be remembered that the Myrobalan root, being at home in Asia
Minor, where alkali abounds, should when practicable be used wherever
alkali conditions exist, in preference to all but the almond, which
seems to resist well, even on its own root, but has not as wide a range
of adaptations as a grafting stock as the myrobalan. While most of the
other stone fruits at the Tulare substation were on myrabalan roots,
the stock of those in outside orchards was mostly in doubt. It is also
to be kept in mind that different varieties of the same fruit—_e.
g._, pears and apples—show a not inconsiderable variation in their
resistance.
_Timber and Shade Trees._
Of trees, forest and shade, suitable for alkali lands, some native ones
call for mention. One is the California white or valley oak (_Quercus
lobata_), which forms a dense forest of large trees on the (almost
throughout somewhat alkaline) delta lands of the Kaweah River in
California, and is found scatteringly all over the San Joaquin Valley.
Unfortunately this tree does not supply timber valuable for aught but
firewood or fence posts, being quite brittle.
The native _cottonwoods_, while somewhat retarded and dwarfed in
their growth in strong alkali, are quite tolerant of the white salts,
especially of Glauber’s salt. As they usually grow near to the water,
their tolerance for alkali salts is difficult to ascertain.
Of other trees, the _oriental plane_, or sycamore, and the _black
locust_ have proved the most resistant in the alkali lands of the San
Joaquin Valley; and the former being a very desirable shade tree, it
should be widely used throughout the regions where alkali prevails more
or less. The _ailantus_ is about equally resistant, and but for the
evil odor of its flowers, deserves strong commendation.
Of the _eucalypts_, the narrow-leaved _Eucalyptus amygdalina_ (one of
the “red gums”) and the closely related _viminalis_, seem to be least
sensitive, and in some cases have grown in alkali lands as rapidly
as anywhere. The _rostrata_, as well as the pink flowered variety of
_sideroxylon_, are now doing about as well as the _amygdalina_ at
Tulare, where at first they seemed to suffer. The common blue gum,
_globulus_, is much more sensitive.
Of the _Acacias_, the tall-growing _A. melanoxylon_ (“black acacia”)
resists pretty strong alkali, even on stiff soil; as can be seen at
Tulare and Bakersfield, California, where there are trees nearly two
feet in diameter. The beautiful _A. lophantha_ (_Albizzia_) has in
plantings made along the San Joaquin Valley railroad shown considerable
resistance, likewise; but it is quite sensitive to frost.
Of other Australian trees, one of the Australian “pines,” (_Casuarina
equisetifolia_), is doing well on fairly strong alkali land in the San
Joaquin Valley.
A remarkably alkali-resistant shrub or small tree is the pretty
_Kœlreuteria paniculata_ from China, which at Tulare is growing in
some of the strongest alkali soil of the tract. Unfortunately it is
available mainly for ornamental purposes; its wood, while small, is
very hard and makes excellent fuel.
Of trees indigenous to the Atlantic and East Central United States,
the Tulip tree, the Linden, and most other trees of the humid region,
including the English oak (_Quercus pedunculata_) become stunted
in alkali soils. The _honey locust_, being particularly adapted to
calcareous lands, does moderately well on alkali lands, but its thorns
and imperfect shade render it not very desirable. The _black locust_
and the _elms_ have on the whole done best. The eastern maples are not
successful; but the California maple (_Acer macrophyllum_) and the box
elder (_Negundo californica_) have done fairly well in the lighter
alkali lands of the San Joaquin Valley.
The _Conifers_—Pines, firs, cedars, cypress, etc., are very sensitive
to black alkali and will not endure much even of the “white” salts.
Even the native juniper of the mesas carefully adheres to the
portions—breaks and upper slopes, hilltops, etc.—which are more or less
leached by the scanty rains of these regions.
INDUCEMENTS TOWARD THE RECLAMATION OF ALKALI LANDS.
The expense involved in the reclamation of strong alkali lands
naturally gives rise to the question whether adequate advantages are
likely to be derived from such expenditure; specially when the last
resort—underdraining and leaching—has to be adopted.
Those familiar with the alkali regions are aware how often the
occurrence of alkali spots interrupts the continuity of fields and
orchards, of which they form only a small part, but enough to mar their
aspect and cultivation. Their increase and expansion under irrigation
frequently renders their reclamation the only alternative of absolute
abandonment of the investments and improvements made, and from that
point of view alone it is of no slight practical importance. Moreover,
the occurrence of vast continuous stretches of alkali lands within the
otherwise most eligibly situated valley lands of the irrigation region
forms a strong incentive towards their utilization.
[Illustration: 1st year, 2d year, 3d year, Fourth year—42 bushels.
FIG. 75.—Wheat grown on black alkali land at Tulare Substation,
California, showing improvement in successive years of reclamation
treatment.]
There is, however, a strong intrinsic reason pointing in the
same direction, namely, the almost invariably high and lasting
productiveness of these lands when once rendered available to
agriculture. This is foreshadowed by the usually heavy and luxuriant
growth of native plants around the margins and between alkali spots
(see fig. 60); _i. e._, wherever the amount of injurious salts
present is so small as not to interfere with the utilization of the
abundant store of plant-food which, under the peculiar conditions of
soil-formation in arid climates, remains in the land instead of being
washed into the ocean. Extended comparative investigations of soil
composition, as well as the experience of thousands of years in the
oldest settled countries of the world, demonstrate this fact and show
that so far from being in need of fertilization, alkali lands usually
possess extraordinary productive capacity whenever freed from the
injurious influence of the excess of useless salts left in the soil in
consequence of deficient rainfall. (See analyses, chapter 22, pp. 436,
437).
[Illustration: FIG. 76.—Grains grown on alkali land at Tulare Station,
California.]
Among many striking examples of the results of such reclamation, is
that represented in the annexed figure (75), of grain grown on strong
alkali land, before and after reclamation treatment. On the original
land even “alkali weeds” would hardly grow; while afterward a wheat
crop representing forty-two bushels per acre was grown. Additional
illustrations are shown in the second figure (76), showing crops of
wheat and barley as grown on partly reclaimed land at the Tulare
substation.
While it is certainly true that when rightly treated, alkali lands can
be rendered profusely and lastingly productive, yet close attention and
constant vigilance are needed so long as the salts remain in the soil;
and no one not determined to give such land such full attention, should
undertake to cultivate it.
PART FOURTH.
SOILS AND NATIVE VEGETATION.