ALKALI SOILS.
_Alkali Lands and Seashore Lands._—Alkali lands proper, as already
stated, are wholly distinct in their nature and origin from the salty
lands of sea-coast marshes, past or present. The latter derive their
salts from sea-water that occasionally overflows them, or from that
which has evaporated in segregated basins or estuaries; and the salts
impregnating them are essentially “sea salts,” that is, common salt,
together with bittern (magnesium chlorid), Epsom salt (magnesium
sulfate) gypsum, etc. (see chapter 2, p. 26). Very little of what would
be useful to vegetation or desirable as a fertilizer is contained in
the salts impregnating such soils; and they are by no means always
intrinsically rich in plant-food, but vary greatly in this respect.
While seashore lands are by no means always of high fertility even when
freed from their salts, especially when very sandy, it is otherwise
when they occur near the mouths of streams or rivers, whose finest
sediments they then receive. From such lands are formed the profusely
productive Polders of Holland and northern Germany, and the equally
noted “colmates” of France and Italy. These, so soon as freed from
salt, may be considered as possessing the same advantages as “delta”
alluvial lands, and from the same causes; notably the accumulation of
the finest sediments derived from the rivers’ drainage basins.
_Origin._—Alkali lands proper bear no definite relation to the present
sea; they are mostly remote from it or from any other sea bed, so
that they have sometimes been designated as “terrestrial salt lands.”
Their existence is in the majority of cases definitely traceable to
climatic conditions alone. They are the natural result of a light
rainfall, insufficient to leach out of the land the salts that always
form in it by progressive weathering of the rock powder of which all
soils largely consist. Where the rainfall is abundant, that portion
of the salts corresponding to “sea salts” is leached out into the
bottom water, and with this passes through springs and rivulets into
the country drainage, to be finally carried to the ocean.[162] Another
portion of the salts formed by weathering, however, is partially or
wholly retained by the soil; it is that portion chiefly useful as plant
food.
[162] See Chapter 2, p. 26.
It follows that when, in consequence of insufficient rainfall, all or
most of the salts are retained in the soil, they will contain not only
the ingredients of sea-water, but also those useful to plants. In rainy
climates a large portion even of the latter is leached out and carried
away. In extremely arid climates, on the contrary, the entire mass of
the salts remains in the soils; and, being largely soluble in water,
evaporation during the dry season brings them to the surface, where
they may accumulate to such an extent as to render ordinary useful
vegetation impossible; as is seen in “alkali spots,” and sometimes in
extensive tracts of “alkali desert.” Three compounds, viz. the sulfate,
chlorid and carbonate of sodium, usually form the main mass of these
saline efflorescences. Magnesium sulfate (Epsom salt) is in many cases
a very abundant ingredient; some calcium sulfate is nearly always
present, and calcium chlorid is not infrequently found.
In some cases the above salts are in part at least derived
from the leaching of adjacent or subjacent geological
deposits impregnated with them at the time of their
formation. Such is the case in portions of Wyoming, Colorado
and New Mexico, in the Colorado river delta, and in the
Hungarian Plain; and it is in these cases especially that
the chlorids of calcium and magnesium also form part of the
saline mixture.
_Geographical Distribution of Alkali Lands._—In looking over a rainfall
map of the globe[163] we see that a very considerable portion of the
earth’s surface, forming two belts to poleward of the two tropics, has
deficient rainfall; the latter term being commonly meant to imply any
annual average less than 20 inches (500 millimeters). The arid region
thus defined includes, in North America, most of the country lying
west of the one hundredth meridian up to the Cascade Mountains, and
northward beyond the line of the United States; southward, it reaches
far into Mexico, including especially the Mexican plateau. In South
America it includes most of the Pacific Slope (Peru and Chile) south to
Araucania; and eastward of the Andes, the greater portion of the plains
of western Brazil and Argentina. In Europe only a small portion of the
Mediterranean border is included; but the entire African coast-belt
opposite, with the Saharan and Libyan deserts, Egypt and Arabia, are
included therein, as well as, south of the Equator, a considerable
portion of South Africa (Kalahari desert). In Asia, Asia Minor, Syria
(with Palestine), Mesopotamia, Persia, and northwestern India up to
the Ganges, and northward, the great plains or steppes of central Asia
eastward to Mongolia and western China, fall into the same category; as
does also a large portion of the Australian continent.
[163] See above, chapter 16, p. 294.
_Utilization of World-wide Importance._—Over these vast areas alkali
lands occur to a greater or less extent, the exceptions being the
mountain regions and adjacent lands on the side exposed to the
prevailing winds. It will therefore be seen that the problem of the
utilization of alkali lands for agriculture is not of local interest
only, but is of world-wide importance. It will also be noted that
many of the countries referred to are those in which the most ancient
civilizations have existed in the past, but which at present, with few
exceptions, are occupied by semi-civilized people only. It is doubtless
from this cause that the nature of alkali lands has until lately been
so little understood, that even their essential distinctness from the
sea-border lands has been but recently recognized in full. Moreover,
the great intrinsic fertility of these lands when freed from the
noxious salts, has been very little appreciated; their repellent aspect
causing them to be generally considered as permanently waste lands.
_Repellent aspect._—This aspect is essentially due
to their natural vegetation being in most cases confined
to plants useless to man, commonly designated as “saline
vegetation,”[164] of which but little is usually relished by
cattle. Notable exceptions to this rule occur in North and
South America, Australia, and Africa, where the “saltbushes”
of the former and the “karroo” vegetation of the latter form
valuable pasture and browsing grounds. Apart from these,
however, all efforts to find culture plants for these lands
generally acceptable, or at least profitable, in their
natural condition, have not been very successful.
[164] See Chapter 23.
[Illustration: FIG. 60.—Alkali Lands in San Joaquin Valley,
California.]
Figure 60 illustrates the usual aspect of alkali lands in
the San Joaquin valley of California. It will be noted that
the alkali-covered surface is only in spots, with clumps of
vegetation between, so that cattle can find both pasture and
browsing on a portion of such lands, even though the plants
so growing are not usually of the most desirable kind. We
find in all arid regions, however, considerable areas either
wholly destitute of vegetation, or bearing only such saline
growth as is rejected by all kinds of domestic animals.
_Effects of Alkali upon culture plants._—In land very strongly
impregnated with alkali salts, most culture plants, if their seed
germinates at all, will show a sickly growth for a short time, “spindle
up” and then die without fruiting. In soils less heavily charged the
plants may simply become dwarfed, and fruit scantily. The effect on
grown trees around which alkali has come up, is first, scanty leafage
and short growth of shoots, themselves but sparsely clothed with
leaves. This state of things is well shown in figures 61 and 62, which
represent apricot trees growing but a short distance apart, but one
coming within range of an expanding alkali spot. The characteristic
sparseness of the foliage of the “alkalied” tree as compared with the
adjacent one is well shown.
_Nature of the injury to plants from Alkali._—When we examine plants
that have been injured by alkali, we will mostly find that the visible
damage has been done near the base of the trunk, or _root crown_;
rarely at any considerable depth in the soil itself. In the case of
green herbaceous stems, the bark is found to have been turned to a
brownish tinge for half an inch or more, so as to be soft and easily
peeled off. In the case of trees, the rough bark is found to be of a
dark, almost black, tint, and the green layer underneath has, as in
the case of herbaceous stems, been turned brown to a greater or less
extent. In either case the plant has been practically “girdled,” the
effect being aggravated by the diseased sap poisoning more or less
the whole stem and roots. The plant may not die, but it will be quite
certain to become unprofitable to the grower.
[Illustration: FIG. 61.—Unaffected.]
[Illustration: FIG. 62.—Yielding to Alkali.
APRICOT TREES ON ALKALI GROUND.]
It is mainly in the case of land very heavily charged with common salt,
as in the marshes bordering the sea, or salt lakes, that injury arises
from the direct effects of the salty soil-water upon the feeding roots
themselves. In a few cases the gradual rise of salt water from below
in consequence of defective drainage, has seriously injured, and even
destroyed, old orange orchards. The natural occupancy of the ground
by certain native plants may be held to indicate that the soil is too
heavily charged with saline ingredients to permit healthy root growth
or nutrition until the excess of salts is removed. (See below, chapters
23 and 26).
The fact that in cultivated land the injury is usually found to
occur near the surface of the soil, concurrently with the well-known
fact that the maximum accumulation of salts at the surface is always
found near the end of the dry season, indicates clearly that this
accumulation is due to evaporation at the surface. The latter is
often found covered with a crust consisting of earth cemented by the
crystallized salts, and later in the season with a layer of whitish
dust resulting from the drying-out of the crust first formed. It is
this dust which becomes so annoying to the inhabitants and travelers
in alkali regions, when high winds prevail, irritating the eyes and
nostrils and parching the lips.
_Effects of Irrigation._—One of the most annoying and discouraging
features of the cultivation of lands in alkali regions is that,
although in their natural condition they may show but little alkali
on their surface, and that mostly in limited spots, these spots are
found to enlarge rapidly as irrigation is practiced. Yet since alkali
salts are the symptoms and result of insufficient rainfall, irrigation
is a necessary condition of agriculture wherever they prevail. Under
irrigation, neighboring spots will oftentimes merge together into one
large one, and at times the entire area, once highly productive and
perhaps covered with valuable plantations of trees or vines, will
become incapable of supporting useful growth. This annoying phenomenon
is popularly known as “the rise of the alkali” in the western United
States, but is equally well known in India and other irrigation regions.
The soil being impregnated with a solution of the alkali salts, and
acting like a wick, the salts naturally remain behind on the surface
as the water evaporates, the process only stopping when the moisture
in the soil is exhausted. We thus not infrequently find that after an
unusually heavy rainfall there follows a heavier accumulation of alkali
salts at the surface, while a light shower produces no perceptible
permanent effect. We are thus taught that, within certain limits, the
more water evaporates during the season the heavier will be the rise of
the alkali; provided that the water is not so abundant as to leach the
salts through the soil and subsoil into the subdrainage.
_Leaky Irrigation ditches._—Worst of all, however, is the effect
of irrigation ditches laid in sandy lands (such as are naturally
predominant in arid regions), without proper provision against seepage.
The ditch water then gradually fills up the entire substrata so far
as they are permeable, and the water-table rises from below until it
reaches nearly to the ditch level; shallowing the subsoil, drowning out
the deep roots of all vegetation, and bringing close to the surface the
entire mass of alkali salts previously diffused through many feet of
substrata.
_Surface and Substrata of Alkali Lands._—Aside from the desert proper,
in the greater portion of the alkali country “alkali spots.” _i. e._
ground covered with saline efflorescences and showing little or no
vegetation, are interspersed with larger areas apparently free from
salts and covered with the ordinary vegetation of the region. A view of
such country is given in a plate on a previous page. The alkali spots
are usually somewhat depressed below the surrounding lands, and after
rains remain covered with water for some time; the water frequently
assuming a brown or blackish tint after standing.
When a pointed steel probe is pushed down within such an alkali spot,
it will usually be found that, although the soil may appear quite
sandy, it is penetrated with some difficulty; while outside of the
spots, the probe does not encounter serious resistance until it reaches
the depth of two or three feet, when it frequently becomes impossible
to penetrate farther without the aid of a hammer. On the margin of the
spots, the transition from utter barrenness to a luxuriant vegetation
of native weeds is mostly quite sudden; as is shown in the figure, p.
425.
_Vertical Distribution of the Salts in Alkali Land._—The results of a
comparative examination of such land before and after irrigation,[165]
are shown in the annexed diagrams; in which the kind and amount of
salts is shown for every three inches of vertical depth, down to four
feet, by curves whose extension from left to right indicate the several
percentages, while the outer curved line gives the total of salts for
each of the several depths.
Fig. 63 represents the condition of the salts in an “alkali
spot” as found at the end of the dry season at the Tulare
substation, California. The soil was sampled to the depth of
two feet at intervals of three inches each. It is easy to
see that at this time the bulk of the salts was accumulated
within the first six inches from the surface, while lower
down the soil contained so little that few culture plants
would be hurt by them.
_How Native Plants Live._—Fig. 64 represents
similarly the state of things in a natural soil alongside
of the alkali spot, but in which the native vegetation of
brilliant flowers develops annually without any hindrance
from alkali. Samples were taken from this spot in March,
near the end of the wet, and in September, near the end of
the dry season, and each series fully analyzed. There was
scarcely a noticeable difference in the results obtained. It
is seen in the figure that down to the depth of 15 inches
there was practically no alkali found (0.035%), and it was
within these 15 inches of soil that the native plants mostly
had their roots and developed their annual growth. But
from that level downward the alkali rapidly increased, and
reached a maximum (0.529%), at about 33 inches; decreasing
rapidly thence until, at the end of the fourth foot in
depth, there was not more alkali than within the first foot
from the surface. In other words, the bulk of the salts
had accumulated at the greatest depth to which the annual
rainfall (7 inches) ever reaches, forming there a sheet of
tough, intractable clay-hardpan. The shallow-rooted native
plants germinated their seeds freely on the alkali-free
surface; their roots kept above the strongly-charged
subsoil, and through them and the stems and foliage all the
soil moisture was evaporated by the time the plants died.
Thus no alkali was brought up from below by evaporation. The
seeds shed would remain uninjured, and would again germinate
the coming season.
[165] Hilgard and Loughridge, Bulletin No. 128, California Experiment
Station; Report California Experiment Station, 1894-95, p. 37; Bulletin
No. 30, Office of Experiment Stations; Wollny’s Forsch. Geb. Agr.
Phys., 1896.
[Illustration: FIG 63.—Diagram showing amounts and composition of
alkali salts at various depths in alkali soil, on which barley would
not grow. Taken September, 1894.
Tulare Experiment Substation, California.]
[Illustration: FIG. 64.—Diagram showing amounts and composition of
alkali salts at various depths in black alkali land, covered with
native vegetation. Taken March, 1895.
Tulare Experiment Substation, California.]
It is thus that the luxuriant vegetation of the San Joaquin plains,
dotted with occasional alkali spots, is maintained; the spots
themselves being almost always depressions in which the rain water may
gather, and where, in consequence of the increased evaporation, the
noxious salts have risen to the surface and render impossible all but
the most resistant saline growth; particularly when, in consequence of
maceration and fermentation in the soil, the formation of carbonate of
soda has caused the surface to sink and become almost water-tight.
_Upward Translocation from Irrigation._—Fig. 65 shows the corresponding
profile of the same soil after several years’ irrigation. The upward
movement of the salts is clearly seen by comparison with the previous
figure; and the surface soil has become so charged with salts that the
seeds of culture plants refuse to germinate.
Ten feet from this bare alkali ground, on which barley had refused to
grow, a crop of barley four feet high was harvested the same year,
without irrigation. Investigation proved that here the condition of
the soil was intermediate between the two preceding diagrams. The
irrigation water had dissolved the alkali of the subsoil, and the more
abundant evaporation had brought it nearer the surface; but the shading
by the barley crop and the evaporation of the moisture through its
roots and leaves had prevented the salts from reaching the surface in
such amounts as to injure the crop, although the tendency to rise was
clearly shown. By the use of gypsum, moreover, the injuriousness of the
alkali had been somewhat diminished.
The same season, grain crops were almost a failure on alkali-free
land in the same region; and in connection with this result it should
be noted as a general fact that alkali lands always retain a certain
amount of moisture perceptible to the hand during the dry season, and
that _this moisture can be utilized by crops_; so that at times when
crops fail on non-alkaline land, good ones are obtained where a slight
taint of alkali exists in the soil. Actual determinations showed that
while a sample of alkali soil containing .54% of salts absorbed 12.3%
of moisture from moist air, the same soil when leached absorbed only
2.5%—a figure corresponding to that of sandy upland loams.
[Illustration: FIG. 65.—Diagram showing amounts and composition of
alkali salts at various depths in bare alkali land, where barley would
not grow; irrigated. Taken September, 1894.
Tulare Experiment Substation, California.]
[Illustration: FIG. 66.—Distribution of Alkali Salts in Sandy Lands.]
_Alkali in Sandy Lands._—In _very_ sandy lands, and particularly when
the alkali is “white” only, the tendency to accumulation near the
surface is much less, even under irrigation. In the natural condition
the salts are in such cases often found quite evenly distributed
through soil columns of four feet, and even more. This is an additional
cause of the lesser injuriousness of “white alkali.” An illustration
of the distribution of the salts in very sandy lands, from the Tulare
substation, is given in Fig. 66. Here we see that the maximum is not
_at_, but some distance below the surface, the entire saline mass is
lower down than in the more clayey loam of the same locality, and is
more widely distributed in depth.
_Distribution of Alkali Salts in Heavy Lands._—The mode of distribution
of alkali salts in the heavier, close-grained soil of the Chino
experimental tract in southern California, is illustrated in Fig. 67.
This land is permanently moist, from a water-table ranging from five
to seven feet below the surface in ordinary years. There is therefore
no opportunity for the formation of “alkali hardpan” as in the case
of the Tulare soil; the salts always remain rather near the surface,
viz. within twelve to fifteen inches. But being in much smaller average
amounts than at Tulare (an average of about 5300 lbs. per acre), quite
a copious natural vegetation of grasses, sunflowers, and “yerba mansa”
covered the whole surface, save in a few low spots.
A similar mode of distribution of the salts is found in the still more
clayey “black adobe” lands of the Great Valley of California. The
scanty rains cannot penetrate these soils to any great depth, so that
evaporation will soon bring the salts carried by them back to within a
short distance of the surface. Their accumulation there is frequently
indicated by the entire absence of any but the most resistant alkali
weeds, even though the total of salts in the land may not be very great.
_Salton Basin._—A peculiar state of things is illustrated in the Salton
Basin, which represents what was at one time the head of the Gulf of
California, and at the lowest point of which, 268 feet below sea level,
there now lies a large deposit of rock salt. It has been cut off from
the present Gulf by the delta deposits of the Colorado river, which
now, however, overflows into the Basin at times of extreme high water.
Although appearing level to the eye, the general slope of the country
is to the lowest point of the former sea-bottom.
The region, now in progress of settlement by means of
irrigation water brought from the river near Yuma, was
investigated with respect to its alkali conditions in 1900
(Bulletin No. 140, Calif. Agric. Expt. Sta.). The annexed
diagram 68 shows the distribution of the salts to a depth of
21 feet. It will be noted that here also the alkali content
becomes insignificant at 4 feet depth, but increases again
to a second maximum at about 15 feet, below which there is a
second decrease; below this, at 20 feet, there is a final
very heavy increase, not only of the total salts but
especially of common salt, which evidently represents the
drainage toward the salt deposit. Above this level there is
a very remarkable predominance of Glauber’s salt (sodium
sulfate), also observable elsewhere, _e. g._ near White
Plains, Nev., whose name is derived from the copious surface
accumulation of the sulfate. It seems as though this must
have been formed in some way from the common salt.
[Illustration: FIG. 67.—Amounts and composition of alkali salts at
various depths and points in the ten-acre tract at the southern
California Experiment Station; taken last week in April, 1895.]
[Illustration: FIG. 68.—Graphic illustration of distribution of salts
in Salton River section, California.]
_Horizontal Distribution of Alkali Salts in Arid Lands._—The constant
occurrence of “alkali spots” in arid lands shows at once the great
inequality of horizontal distribution of alkali impregnation. This
is as prominent in level lands as on slopes, and in extremely arid
regions it is mostly not possible to recognize even very considerable
differences without close examination. Thus in lands appearing exactly
alike on the surface, on the edge of the Salton basin in California,
on the same forty acre 1.4% (56,000 pounds per acre) was found in
the surface four feet at one point, and a hundred yards away, 12.5%
(500,000 pounds). The mapping of alkali lands is therefore somewhat
precarious unless carried into great detail. Moreover, it has been
found that the location of the salts changes from year to year,
especially in irrigated land, as might be expected. Those cultivating
alkali lands have therefore to exercise constant watchfulness, unless
the salts have been definitively eliminated by underdrainage over
a considerable area; as merely local operations may be rendered
ineffectual by the migration of the salts from neighboring tracts not
reclaimed.
_Alkali in Hill Lands._—As a rule, hill lands themselves are remarkably
free from alkali, even in the arid regions; except when water is
gathered in depressions, where strongly saline waters may be found in
Washington, Montana and elsewhere. But on level plateau lands, where
drainage is slow or imperfect, alkali appears as freely as it does in
the same regions in the stream bottoms. In the latter the leachings and
seepage of the uplands naturally causes a concentration of the salts,
and thus we find alkali salts incrusting the surface in the valleys of
the streams, as _e. g._, that of the Yellowstone, Musselshell, Judith,
Yakima and others in the north, and of Green river, Platte, Pecos, and
Rio Grande farther south; as well as in numerous valleys of central and
southern California.
_Usar Lands of India._—These lands have been investigated first by
the “Reh Commission” appointed to investigate the causes of the
deterioration of lands in the Aligarh district (south of Delhi,
between the Ganges and Jumna rivers), in 1876. The occasion of this
appointment was the appearance of “reh” (alkali salts) in a region
which had previously been free from them.[166] Subsequently, a more
elaborate investigation of the subject was made by Dr. J. W. Leather,
Agricultural Chemist to the Government of India.[167] From these
documents it appears that “usar lands” exist largely not only in the
Northwestern Provinces and Oudh, but also in the Panjab, especially
on the lands bordering the Chenab river; likewise to a slight extent
in the Bombay presidency. Leather’s investigation shows that not all
the lands designated by the natives as _usar_ contain soluble salts in
injurious amounts, some being simply lands having very hard, clayey
soils difficult to till with the imperfect methods employed. Yet the
general phenomena of the true “reh” lands are practically identical
with those of the American alkali lands, including also the calcareous
hardpan, there called _kankar_. Owing probably to the long cultivation
of the Indian lands (mostly under irrigation), the salts are there at
their maximum in the first foot, decreasing as depth increases. It is
noteworthy also that in the majority of cases the predominant salt is
carbonate of soda or black alkali, which there as in California renders
the lands impervious to water until treated with gypsum. This fact
accounts for the popular use of the same name for non-saline impervious
clay soils, and the alkali or reh lands proper.
We have an entirely analogous case in the “Szek” lands of the Hungarian
plain, some of which are simply poor refractory soils containing a
trace of soluble salts; while lower down in the valley of the Theiss
we find genuine alkali lands, both black and white, which have long
furnished carbonate of soda for local use and commerce. In this case,
however, the alkali salts seen to come largely, in some cases wholly,
from underlying saline clays whose salts in coming to the surface
suffer precisely the same transformations experienced in California and
India, in presence of calcic carbonate (see below, p. 450 ff).
[166] An abstract of the report of this commission is given in the
Report of the California Experiment Station for 1890.
[167] See Agricultural Ledger, 1897, No. 13; ibid. 1901, No. 13.
The accounts given by v. Middendorff of the nature and occurrence of
alkali lands in Turkestan (Ferghana) agree entirely with those given
above for California and India; as do also the investigations made by
other Russian observers on the saline lands of the steppes of European
Russia.
COMPOSITION AND QUANTITY OF ALKALI SALTS.
_Black and White Alkali._—Broadly speaking, the world over alkali
salts consist mainly of three chief ingredients, already mentioned,
namely, common salt, Glauber’s salt (sulfate of soda), and salsoda or
carbonate[168] of soda. The latter causes what is popularly known as
“black alkali,” from the black spots of puddles seen on the surface of
lands tainted with it, owing to the dissolution of the soil humus;[169]
while the other salts, often together with Epsom salt and bittern
(Magnesium chlorid), constitute “white alkali,” which is known to
be very much milder in its effect on plants than the black. In most
cases all three are present, and all may be considered as practically
valueless, or noxious, to plant growth.
[168] In this designation are included, in this volume, both the
normal (mono-) carbonate and the two other compounds, the bi- or
hydrocarbonate and the intermediate (so-called sesqui-) compound or
trona; all of which are commonly present simultaneously, but in utterly
indefinite relative proportions, varying from day to day and from
inch to inch of depth, inasmuch as their continued existence depends
upon the greater or less formation of carbonic acid in the soil, and
the access of air. Hence their separate quantitative determination
at any one time is of little practical interest. All naturally
occurring carbonate of soda contains, and sometimes consists of, these
“super-carbonates,” according to the greater or less exposure to air
and solar heat. They are much milder in their action on plants than the
monocarbonate, which unfortunately, in the nature of the case, always
predominates near the surface, and thus injures the root-crown.
[169] A wholly different kind of “black alkali” exists in some regions,
especially in the delta lands of the Colorado of the West and in the
Pecos and Rio Grande country in New Mexico. In these cases the dark
tint is due, not to a humic solution, but simply to moisture, which
is tenaciously retained by the chlorids of calcium and magnesium
impregnating the land, thus contrasting strongly with the gray tint of
the general dry soil.
=========================+=================+=========================
| EUROPE. | ASIA.
|-----------------+-----------------+-------
| HUNGARIAN | ARALO-CASPIAN | ADEN.
| PLAIN. | PLAIN. |“HURKA”
| “SZEKSO.” | SALINE CRUSTS.|“KARA.”
+---------+-------+ |
|Debreczin|Kalocsa| |
| | | |
| | | |
-------------------------+---------+-------+-----+-----+-----+-------
| | | | | |
Potassium Sulfate (K₂SO₄)| | | | | |
Sodium Sulfate (Na₂SO₄) | .2 | 1.6| 10.4| 18.2| 15.5|
Sodium Carbonate (Na₂CO₃)| 48.1 | 92.5| 14.7| 12.1| 69.0| 67.2
Sodium Chlorid (NaCl) | 51.7 | 4.4| 74.6| 69.7| 15.5| 32.8
Sodium Phosphate (Na₃PO₄)| | 1.5| | | |
Calcium Chlorid | | | | | |
Magnesium Chlorid (MgCl₂)| | | | | |
+---------+-------+-----+-----+-----+-------
| 100.0 | 100.0|100.0|100.0|100.0| 100.0
-------------------------+---------+-------+-----+-----+-----+-------
=========================+======================================
| ASIA.
|--------------------------------------
| INDIA
| “REH.”
+--------------------------------------
| |Gursikar,|Jellalabad,|Bayamati
| |Aligarh, |Panjab, |(Regur),
| |6 feet. |1.5 feet. |Deccan,
| | | |2 feet.
-------------------------+-------+---------+-----------+--------
| | | |
Potassium Sulfate (K₂SO₄)| 11.1 | | |
Sodium Sulfate (Na₂SO₄) | 7.0 | 15.5 | 58.5 | 2.3
Sodium Carbonate (Na₂CO₃)| 79.0 | 56.9 | 22.9 |
Sodium Chlorid (NaCl) | 2.9 | 27.6 | 18.6 | 97.7
Sodium Phosphate (Na₃PO₄)| | | |
Calcium Chlorid | | | |
Magnesium Chlorid (MgCl₂)| | | |
+-------+---------+-----------+--------
| 100.0 | 100.0 | 100.0 | 100.0
-------------------------+-------+---------+-----------+--------
=========================+======================================
| AFRICA.
+--------------------------+-------------
| EGYPT. |
| |
+---------------+----------+
| Trona, | Alkali | Fezzan
| (Commercial.) |L. Abukir.| Trona,
| | |(Commercial.)
| | |
-------------------------+------+--------+----------+-------------
| | | |
Potassium Sulfate (K₂SO₄)| | | 6.49 |
Sodium Sulfate (Na₂SO₄) | 23.6 | 38.3 | .82 | 0.6
Sodium Carbonate (Na₂CO₃)| 28.2 | 47.7 | 1.13 | 98.7
Sodium Chlorid (NaCl) | 48.2 | 14.0 | 89.74 | .7
Sodium Phosphate (Na₃PO₄)| | | |
Calcium Chlorid | | | 1.82 |
Magnesium Chlorid (MgCl₂)| | | |
+------+--------+----------+-------------
|100.0 | 100.0 | 100.00 | 100.0
-------------------------+------+--------+----------+-------------
===========================+========================================
| CALIFORNIA.
+------+---------+----------------+------
| | | Tulare County. |
|Merced|Overhiser+-------+--------+ Kern
|Falls.| San |Visalia| Expt. |Island
| | Joaquin | |Station.|
| | Co. | |Tulare. |
---------------------------+------+---------+-------+--------+------
Potassium Chlorid, KCl | | | | |
Potassium Sulfate, K₂SO₄ | | 20.23 | 3.95| 10.13|
Potassium Carbonate. K₂CO₃ | | | | |
Sodium Sulfate, Na₂SO₄ | 4.67| 13.00 | | 25.28| 88.42
Sodium Nitrate, NaNO₃ | 12.98| | | 19.78|
Sodium Carbonate, Na₂CO₃ | 75.95| 52.22 | 65.72| 32.58| 0.42
Sodium Chlorid, (NaCl) | 1.46| 33.00 | 3.98| 14.75| 0.51
Sodium Phosphate, HNa₂PO₄ | 4.94| 1.78 | 8.42| 2.25|
Magnesium Sulfate, MgSO₄ | | | 1.65| | 0.52
Calcium Chlorid | | | | |
Magnesium Chlorid | | | | |
Ammonium Carbonate, NH₄CO₃ | | | | 1.41|
---------------------------+------+---------+-------+--------+------
|100.00| 100.00 | 100.00| 100.00|100.00
---------------------------+------+---------+-------+--------+------
===========================+========================================
| CALIFORNIA.
+-------+----------+-----------+---------
| | | |
| Mojave| Hunts, |Westminster| Imperial
|Plateau| near | near |
| | San | Santa Ana.|
| |Bernardino| |
---------------------------+-------+----------+-----------+---------
Potassium Chlorid, KCl | | | | 1.15
Potassium Sulfate, K₂SO₄ | 0.92 | 5.31 | 20.62 |
Potassium Carbonate. K₂CO₃ | | | 6.59 |
Sodium Sulfate, Na₂SO₄ | 43.34 | 66.08 | |
Sodium Nitrate, NaNO₃ | | | | 8.21
Sodium Carbonate, Na₂CO₃ | 15.38 | 15.85 | 62.22 | .58
Sodium Chlorid, (NaCl) | 39.34 | 11.47 | 10.57 | 31.82
Sodium Phosphate, HNa₂PO₄ | 1.02 | | |
Magnesium Sulfate, MgSO₄ | | 0.59 | |
Calcium Chlorid | | | | 58.42
Magnesium Chlorid | | | | 2.81
Ammonium Carbonate, NH₄CO₃ | | | |
---------------------------+-------+----------+-----------+---------
|100.00 | 100.00 | 100.00 | 100.00
---------------------------+-------+----------+-----------+---------
=======================+====================================
| WASHINGTON.
+--------+--------+--------+----------
| Yakima| | | Spokane
| Co. |Kittitas| Whitman| Co.,
| on |Valley. | Co., |Cottonwood
| Atahnam| | Lake | Springs.
| Creek.| | Creek. |
---------------------------+--------+--------+--------+----------
Potassium Chlorid, KCl | 3.90 | 0.16 | 4.53 | 6.27
Potassium Sulfate, K₂SO₄ | 18.44 | 15.17 | 15.90 |
Potassium Carbonate. K₂CO₃ | | | |
Sodium Sulfate, Na₂SO₄ | | | |
Sodium Nitrate, NaNO₃ | 75.61 | 80.36 | 77.10 | 87.14
Sodium Carbonate, Na₂CO₃ | 0.52 | 1.76 | 1.34 | 4.03
Sodium Chlorid, (NaCl) | 1.53 | 2.55 | 1.13 | 2.56
Sodium Phosphate, HNa₂PO₄ | | | |
Magnesium Sulfate, MgSO₄ | | | |
Calcium Chlorid | | | |
Magnesium Chlorid | | | |
Ammonium Carbonate, NH₄CO₃ | | | |
---------------------------+--------+--------+--------+----------
| 100.00 | 100.00 | 100.00 | 100.00
---------------------------+--------+--------+--------+----------
========================+===========================================
| MONTANA.
------------------------+-------------------------------------------
| UPPER MISSOURI VALLEY.
+-----------+-------+------+-------+--------
| Upper |Prickly| Ford | Fort |Robert’s
| Missouri | Pear | on |Benton.| Creek,
| Valley |Plain. | Sun | | Mussel-
| near |Helena.|River.| | shell
|Centerville| | | | Valley.
------------------------+-----------+-------+------+-------+--------
| | | | |
Potassium Sulfate, K₂SO₄| 2.37 | 3.07| 1.77| 8.59| 3.07
Sodium Sulfate, Na₂SO₄ | 56.54 | 43.38| 83.35| 47.10| 76.79
Sodium Nitrate, NaNO₃ | 9.39 | | | |
Sodium Carbonate, Na₂CO₃| | | | .71| 13.99
Sodium Chlorid, NaCl | 27.47 | 14.60| 0.91| .18| 6.15
Magnesium Sulfate, MgSO₄| 4.23 | 38.94| 13.97| 43.42|
Potassium Chlorid, KCl | | | | |
+-----------+-------+------+-------+--------
| 100.00 | 100.00|100.00| 100.00| 100.00
------------------------+-----------+-------+------+-------+--------
========================+==============================
| NEVADA.
|--------------------+---------
| |
| NEAR RENO. | Churchill
| | County.
------------------------+----------+---------+---------
| | |
Potassium Sulfate, K₂SO₄| | |
Sodium Sulfate, Na₂SO₄ | 52.15 | 80.30 | 0.55
Sodium Nitrate, NaNO₃ | | |
Sodium Carbonate, Na₂CO₃| 45.37 | 15.24 | 96.78
Sodium Chlorid, NaCl | 2.48 | 4.46 | 2.67
Magnesium Sulfate, MgSO₄| | |
Potassium Chlorid, KCl | | |
+----------+---------+---------
| 100.00 | 100.00 | 100.00
------------------------+----------+---------+--------
========================+=========================================
| WYOMING.
|----------------------+------------------
| SWEET WATER | LARAMIE FARM.
| VALLEY. |
|-------------+--------+-------+----------
|Independence,| Saint |Alkali.| Waste
| Rock | Mary’s | |Irrigation
| Lake. |Station.| | Water.
------------------------+-------------+--------+-------+----------
| | | |
Potassium Sulfate, K₂SO₄| | | |
Sodium Sulfate, Na₂SO₄ | 73.17 | 88.93 | 59.29| 41.19
Sodium Nitrate, NaNO₃ | | | |
Sodium Carbonate, Na₂CO₃| 22.98 | | |
Sodium Chlorid, NaCl | 3.85 | 11.63 | 17.01| 2.18
Magnesium Sulfate, MgSO₄| | | 23.70| 43.82
Potassium Chlorid, KCl | | | | 12.81
+-------------+--------+-------+----------
| 100.00 | 100.00 | 100.00| 100.00
------------------------+-------------+--------+-------+----------
========================+=========================================
| COLORADO.
+------------+---------+--------+-------
| Near | Grand | Rocky | Rocky
| Denver. |Junction.| Ford. | Ford.
------------------------+------------+---------+--------+-------
Potassium Sulfate, K₂SO₄| | | 0.10 | 13.74
Sodium Sulfate, Na₂SO₄ | 93.40 | 56.05 | 62.54 | 17.36
Sodium Carbonate, Na₂CO₃| | 18.97 | 2.08 | 5.53
Sodium Chlorid, NaCl | 6.60 | 24.98 | 3.86 | 11.53
Magnesium Sulfate, MgSO₄| | | 31.42 | 44.43
Magnesium Chlorid, MgCl₂| | | | 5.76
Magnesium Phosphate | | | | 1.65
+------------+---------+--------+-------
| 100.00 | 100.00 | 100.00 | 100.00
------------------------+------------+---------+--------+-------
========================+=========================================
| NEW MEXICO.
+-------------------------------------------
| PECOS VALLEY.
|------------------------+------------------
| ROSWELL REGION. | CARLSBAD REGION.
+-------+--------+-------+--------+---------
|Bremond|Michelet|Roswell|Carlsbad|Delaware
| | | | | River
------------------------+-------+--------+-------+--------+---------
Potassium Sulfate, K₂SO₄| | | | |
Sodium Sulfate, Na₂SO₄ | 54.61 | 2.62 | 67.46 | 35.16 | 37.11
Sodium Carbonate, Na₂CO₃| | | | |
Sodium Chlorid, NaCl | 51.60 | 65.16 | 10.00 | 26.88 | 34.31
Magnesium Sulfate, MgSO₄| 13.79 | 32.22 | 22.54 | 38.06 | 28.58
Magnesium Chlorid, MgCl₂| | | | |
Magnesium Phosphate | | | | |
+-------+--------+-------+--------+---------
|100.00 | 100.00 |100.00 | 100.00 | 100.00
------------------------+-------+--------+-------+--------+---------
_Nutritive Salts in Alkali._—With them, however, there are almost
always associated, in varying amounts, sulfate of potash, phosphate of
soda, and nitrate of soda, representing the three elements—potassium,
phosphorus, and nitrogen—upon the presence of which in the soil in
available form, the welfare of our crops so essentially depends, and
which we aim to supply in fertilizers. The potash salt is usually
present to the extent of from 5 to 20 per cent of the total salts;
phosphate, from a fraction of one to as much as 4 percent; the nitrate
from a fraction of one to as much as 20 percent. In black alkali the
nitrate is usually low, the phosphate high; in the white, the reverse
is true. Both relations are readily intelligible from a chemical and
bacteriological point of view.
_Estimation of Total Alkali in Land._—The investigations detailed
above having shown that in California at least, outside of the axes
of valleys no practically important amount of alkali salts is usually
found at a depth exceeding four feet, it became possible to determine
approximately the amounts of salts that would have to be dealt with
when irrigation and evaporation should bring the entire amount to or
near the surface; a necessary prerequisite to the determination of
possible cultures. While, as already shown, the salts occur lower down
in very sandy lands, yet the diagram on p. 435 shows that even then, an
estimate on this basis would not be very wide of the truth. It is at
least probable that the same is measurably true of level alkali lands
elsewhere, when not underlaid by geological deposits impregnated with
salts.
The total amount of these salts ordinarily found in alkali lands (_i.
e._ in such as in the dry season show saline efflorescences on the
surface) is from about one tenth of one per cent to as much as three
per cent of the weight of the soil, taken to the depth of four feet.
The percentage of salts having been determined in samples representing
a tract, it becomes easy to calculate, approximately, the total amounts
of each salt present per acre, on the basis of the weight of the soil
per acre foot. For the soils of the arid region, such weight will
usually range from three million five hundred thousand to four million
pounds per acre-foot; the latter being the most usual figure, of which
it may be conveniently remembered, that forty thousand pounds represent
1 per cent. We are thus enabled to estimate _e. g._ the amount of
gypsum required to neutralize the carbonate of soda in the salts, or
the amounts of valuable nutritive ingredients—potash, phosphoric acid
and nitrates—present in the land in the water-soluble form.
As has been shown in the preceding discussion, the analysis at the
surface foot alone, which has frequently been alone made, gives
no definite clew whatever to the _total_ amounts of salts to be
controlled. A _full_ estimate is of special importance in enabling us
to forecast what culture plants are likely to succeed on a given tract,
by reference to the table of “tolerances” given below (chapter 23, page
467).
_Composition of Alkali Soils as a Whole._—As may be imagined, the
presence of the alkali salts finds expression in the analytical
statement of their composition, although not to the extent usually
anticipated from their superficial aspect. The table annexed gives
the composition of fourteen alkali soils, taken to the depth of one
foot, at times when there was no visible accumulation of salts on the
surface. The averages of the several ingredients determined are given
in the fifteenth column, and a comparison of its figures with those
of the general table on page 377 of chapter 20 will show some marked
characteristics. We find the average potash-content to be but little
less than twice as great as in the general average for the state of
California; in the case of lime the ratio is nearly as one to three,
in the case of magnesia nearly one to two; in that of phosphoric acid,
one to two and a half, of which in the presence of carbonate of soda
an unusually large proportion is in a readily soluble, often in the
water-soluble, condition (see preceding table).
The usual proportion of soda, of one-fourth to one-half of the
amount of potash, is changed to one-half or three-fourths; in the
case of the strongest alkali lands soda may equal or even exceed the
potash content. As the latter, however, is invariably high to very
high, it does not happen as frequently as might be supposed that the
soda content exceeds that of potash as shown by the usual method of
soil-extraction with water.
That the _potash_ percentage should always be high in
alkali lands, is hardly surprising when it is considered
that the continued presence of the salts resulting from rock
decomposition affords opportunity for the full exercise of
the preference with which potash is known to be retained in
soils by the formation of complex zeolitic silicates. In
most cases the potash-percentage exceeds .75%, and rises as
high as 2.0%; as is shown in the table.
COMPOSITION OF ALKALI SOILS AS A WHOLE.
(A) = White Ash, Fresno.
(B) = Wire Grass, Visalia.
(C) = Plains, Cross Creek, Tulare
(D) = Salt Grass, B. V. Slough.
=============================+========+========+========+========
| | | |
COLLECTION NUMBER. | (A) | (B) | (C) | (D)
| —704— | —585— | —573— | —700—
-----------------------------+--------+--------+--------+--------
Coarse Materials > 0.55 mm | |14.29 | 1.50 |
Fine Earth | |85.71 |98.50 |
| | | |
CHEMICAL ANALYSIS OF | | | |
FINE EARTH. | | | |
-----------------------------+--------+--------+--------+---------
Insoluble matter |85.87 |66.47 |66.08 |87.06
| 88.58| 71.42| 69.46| 89.04
Soluble silica | 2.71 | 4.95 | 3.38 | 1.98
-----------------------------+--------+--------+--------+--------
Potash (K₂O) | .34 | 1.22 | 1.82 | .49
Soda (Na₂O) | .25 | .68 | .44 | .35
Lime (CaO) | 1.16 | 3.04 | 4.31 | 1.20
Magnesia (MgO) | .50 | .09 | 1.59 | 1.07
Bro. ox. of Manganese (Mn₃O₄)| .03 | .03 | .08 | .03
Peroxid of Iron (Fe₂O₃) | 3.28 | 5.82 | 6.04 | 5.82
Alumina (Al₂O₃) | 3.22 | 7.14 | 8.69 | .17
Phosphoric acid (P₂O₅) | .10 | .24 | .74 | .08
Sulfuric acid (SO₃) | .12 | .66 | .26 | .13
Carbonic acid (CO₂) | | 2.55 | 2.53 |
Water and organic matter | 1.79 | 7.09 | 4.15 | 1.13
+--------+--------+--------+--------
Total |99.37 |99.97 |99.51 |99.51
+--------+--------+--------+--------
Chlorin, per cent. | | | |
Humus | .60 | 1.00 | 1.00 | .17
“ Ash | .35 | .84 | .74 | .20
+--------+--------+--------+--------
“ Nitrogen, per cent. | | | |
in Humus |18.66 |14.10 | |
+--------+--------+--------+--------
“ “ , per cent. | | | |
in soil | .11 | .15 | |
+--------+--------+--------+--------
Hygroscopic Moisture | 2.22 | 8.53 | 8.74 | 2.16
absorbed at °C | | | 14° | 15°
-----------------------------+--------+--------+--------+--------
| Tulare Lake Alluvium,
| Tulare County.
COLLECTION NUMBER. | —891— —893— —77—
-----------------------------+-----------+----------+-------
Coarse Materials > 0.55 mm | | | 4.10
Fine Earth | all | all | 95.90
| | |
CHEMICAL ANALYSIS OF | | |
FINE EARTH. | | |
-----------------------------+-----------+----------+-------
Insoluble matter | 54.71 | 56.92 | 67.34
| 64.55| 67.15|
Soluble silica | 9.84 | 10.13 |
-----------------------------+-----------+----------+-------
Potash (K₂O) | 2.02 | 1.65 | 1.05
Soda (Na₂O) | 2.73 | .54 | .84
Lime (CaO) | 2.46 | 2.96 | 6.51
Magnesia (MgO) | 2.93 | 3.12 | 3.69
Bro. ox. of Manganese (Mn₃O₄)| .03 | .04 | .04
Peroxid of Iron (Fe₂O₃) | 7.46 | 6.73 | 5.05
Alumina (Al₂O₃) | 11.50 | 10.35 | 7.97
Phosphoric acid (P₂O₅) | .11 | .16 | .32
Sulfuric acid (SO₃) | .01 | .01 | .08
Carbonic acid (CO₂) | 1.81 | .93 | 4.42
Water and organic matter | 4.34 | 5.77 | 3.71
+-----------+----------+-------
Total | 99.95 | 99.92 | 101.29
+-----------+----------+-------
Chlorin, per cent. | | |
Humus | | .88 | .47
“ Ash | | 1.03 | 2.18
+-----------+----------+-------
“ Nitrogen, per cent. | | |
in Humus | | | 9.37
+-----------+----------+-------
“ “ , per cent. | | |
in soil | | | .05
+-----------+----------+-------
Hygroscopic Moisture | 10.50 | 8.6 |
absorbed at °C | 10° | 10° |
-----------------------------+-----------+----------+-------
COMPOSITION OF ALKALI SOILS AS A WHOLE.
============================+==========+===============+============
| Tulare |Ten-acre tract.|Carisa Plain
COLLECTION NUMBER |Substation|Chino, S.B. Co.| S.L. Obispo
| | |
| —1159— | —1284— | —1423—
----------------------------+----------+---------------+------------
Coarse Materials > 0.55mm. | 1.96 | 1.00 | 9.00
Fine Earth. | 98.04 | 99.00 | 91.00
| | |
CHEMICAL ANALYSIS OF | | |
FINE EARTH. | | |
----------------------------+----------+---------------+------------
Insoluble matter | 72.98 | 62.62 | 57.33
| 73.58| 70.92 | 69.48
Soluble silica | 6.60 | 18.30 | 12.15
----------------------------+----------+---------------+------------
Potash (K₂O) | 1.20 | .95 | 1.23
Soda (Na₂O) | .52 | .50 | .77
Lime (CaO) | 1.86 | 5.07 | 4.46
Magnesia (MgO) | 1.81 | .84 | 3.12
Br. ox. of Manganese (Mn₃O₄)| .08 | .06 | .01
Peroxid of Iron (Fe₂O₃) | 6.86 | 6.43 | 7.65
Alumina (Al₂O₃) | 5.66 | 4.88 | 6.16
Phosphoric acid (P₂O₅) | .10 | .21 | .43
Sulfuric acid (SO₃) | .03 | .06 | .06
Carbonic acid (CO₂) | | 3.76 |
Water and organic matter | 2.54 | 1.02 | 2.63
Total | 100.24 | 99.70 | 99.99
+----------+---------------+------------
Chlorin, per cent | | .12 |
Humus, per cent | .37 | 1.99 | 1.39
“ Ash, per cent | .32 | 1.13 | .95
+----------+---------------+------------
“ Nitrogen, per cent. | | |
in Humus | 16.75 | 10.20 | 14.36
“ “ , per cent. | | |
in soil | .06 | .20 | .06
+----------+---------------+------------
Hygroscopic Moisture | | 5.81 | 8.46
absorbed at °C | | 15° | 15°
----------------------------+----------+-----------+---+------------
| Perris Valley, |Sand, Coachella,
COLLECTION NUMBER |Jacinto river, Jacinto| Riverside
| Plain, Riverside Co. | Co.
| —1758— | —1760— | —2471—
----------------------------+-----------+----------+----------------
Coarse Materials > 0.55mm. | 7.50 | 3.50 |
Fine Earth. | 92.50 | 96.50 | all
| | |
CHEMICAL ANALYSIS OF | | |
FINE EARTH. | | |
----------------------------+-----------+----------+----------------
Insoluble matter | 41.59 | 35.20 | 58.95
| 63.13 | 58.95| 77.54
Soluble silica | 21.54 | 23.75 | 11.37
----------------------------+-----------+----------+----------------
Potash (K₂O) | 1.37 | 1.16 | 1.26
Soda (Na₂O) | 1.97 | .96 | .37
Lime (CaO) | 4.23 | 8.00 | 2.71
Magnesia (MgO) | 3.80 | 5.69 | 2.20
Br. ox. of Manganese (Mn₃O₄)| .03 | .04 | .05
Peroxid of Iron (Fe₂O₃) | 9.65 | 7.33 | 6.43
Alumina (Al₂O₃) | 7.26 | 6.29 | 5.53
Phosphoric acid (P₂O₅) | .23 | .28 | .21
Sulfuric acid (SO₃) | .34 | .21 | .08
Carbonic acid (CO₂) | 4.19 | 6.49 | 1.05
Water and organic matter | 2.89 | 4.71 | 2.55
Total | 99.81 | 99.84 | 99.98
+-----------+----------+----------------
Chlorin, per cent | | Trace. |
Humus, per cent | .60 | .91 | .46
“ Ash, per cent | .92 | 1.75 | .42
+-----------+----------+----------------
“ Nitrogen, per cent. | | |
in Humus | 6.66 | 7.70 |
“ “ , per cent. | | |
in soil | .04 | .07 |
+-----------+----------+----------------
Hygroscopic Moisture | 9.43 | 8.85 | 2.64
absorbed at °C | 15° | 15° | 15°
----------------------------+-----------+----------+----------------
============================+===============+===========
|Silt, Imperial,|Average of
COLLECTION NUMBER | S. Diego Co. | soils.
| —2325— |
----------------------------+---------------+-----------
Coarse Materials > 0.55mm. | |
Fine Earth. | all |
| |
CHEMICAL ANALYSIS OF | |
FINE EARTH. | |
----------------------------+---------------+-----------
Insoluble matter | 62.67 | 63.08
| 73.60 | 72.19
Soluble silica | 10.93 | 9.11
----------------------------+---------------+-----------
Potash (K₂O) | .74 | 1.17
Soda (Na₂O) | .29 | .78
Lime (CaO) | 3.75 | 3.71
Magnesia (MgO) | 1.68 | 2.29
Br. ox. of Manganese (Mn₃O₄)| .01 | .04
Peroxid of Iron (Fe₂O₃) | 3.71 | 6.30
Alumina (Al₂O₃) | 4.26 | 6.65
Phosphoric acid (P₂O₅) | .22 | .20
Sulfuric acid (SO₃) | .36 | .17
Carbonic acid (CO₂) | 2.32 | 2.14
Water and organic matter | 8.93 | 4.19
Total | 99.87 |
+---------------+-----------
Chlorin, per cent | |
Humus, per cent | .65 | .75
“ Ash, per cent | .69 | .82
+---------------+-----------
“ Nitrogen, per cent. | |
in Humus | 10.90 |
“ “ , per cent. | |
in soil | .07 |
+---------------+-----------
Hygroscopic Moisture | 2.98 | 5.63
absorbed at °C | 15° | 15°
----------------------------+---------------+-----------
This table exhibits also another standing characteristic of alkali
soils, which is to be anticipated from the conditions of their
formation; viz, high _lime-content_, which sometimes rises to the
extent of marliness.
In _phosphates_, also, alkali soils are almost always high; and an
unusually large proportion is found to be readily soluble.
In presence of much carbonate of soda, _nitrates_ are usually scarce
or altogether absent; while owing to the action of the alkaline
solution upon the humus, ammonia salts, or even free (or carbonated
and therefore readily dissociated and assimilated) _ammonia_ may be
present, so as to be perceptible to the senses by its odor in hot
sunshine. But in the case of “white alkali,” more especially of the
sulphate in moderate amounts, nitrification is exceedingly active and
nitrates may sometimes rise to as much as 20% of the soluble salts. As
alkali spots are usually low in the central portion and therefore more
moist than around the edges, we sometimes find ammonia salts in the
middle of a spot, while nitrates are abundant along the margin of the
same. These differences, first demonstrated by an investigation made
by Colmore,[170] illustrate some of the reactions that are essentially
concerned in the agricultural availability of alkali lands. A summary
of Colmore’s results is given in the table below.
[170] Report of the California Exp’t. St’n. for 1892-94, p. 141.
_Cross Section of an Alkali Spot._—The spot examined lies outside of
Tulare, California, substation; it being late in the season, when the
bulk of the salts is found near the surface, the samples were taken to
the depth of one foot only, at points four feet apart, from the center
out.
AMOUNT AND COMPOSITION OF SALTS IN ALKALI SPOT FROM CENTER TO
CIRCUMFERENCE. 4 FEET APART, 1 FT. DEPTH.
======================+========+========+========+========+========
| 1 | 2 | 3 | 4 | 5
Mineral Salts. | Center | Four | Eight | Twelve | Outer
|of spot.| feet. | feet. | feet. | margin.
----------------------+--------+--------+--------+--------+--------
Potassium sulfate | 6.70 | 9.55 | 11.92 | 19.26 | 13.95
Sodium sulfate | 19.84 | 12.85 | 23.72 | 23.97 | 16.96
Magnesium sulfate | 3.07 | .07 | .95 | 2.05 | 8.29
Sodium chlorid | 13.80 | 23.73 | 24.12 | 24.23 | 29.69
Sodium carbonate | 50.72 | 50.96 | 37.55 | 35.49 | 29.94
Sodium phosphate | 5.57 | 2.88 | .87 | ? | 1.04
Sodium nitrate | .30 | ? | .87 | ? | .13
| ------ | ------ | ------ | ------ | ------
Totals | 100.00 | 100.00 | 100.00 | 100.00 | 100.00
| | | | |
Organic matter | 30.00 | 24.80 | 19.48 | 23.36 | 20.31
Total soluble in soil | .78 | .54 | .70 | .37 | .34
Mineral salts | .38 | .40 | .54 | .25 | .23
----------------------+--------+--------+--------+--------+--------
While the table shows an obvious irregularity in some of the data
at the eight-foot point, arising doubtless from an irregularity of
surface or of texture overlooked in taking the samples, we find a very
remarkable regularity of progression in the cases of potassium sulfate,
sodium chlorid, sodium carbonate and sodium phosphate in the other
four samples. The maxima of the “black alkali” and the soluble organic
matter (humus) coincide, as does that of the phosphate; the total
mineral salts at the outer margin are only a little over half of what
is found at the center. This is natural, as owing to the deflocculating
effect of the black alkali, the center is nearly a foot lower than the
margin. The lowering of the nitrate-content at the outer margin is
obviously due to the luxuriant vegetation growing adjacent.
_Reactions between the Carbonates, Chlorids and Sulfates of Alkalies
and Earths._ That a soluble earth-salt, such as the sulfate or chlorid
of calcium, will react upon an alkaline carbonate solution so as to
form an alkali sulfate, and _e.g._ lime carbonate, is well known; the
neutralization of the sodic carbonate in the soil by means of gypsum,
above referred to, is based upon this reaction. It is not so well known
that the latter may be reversed, partly or wholly, by the presence of
carbonic acid in the solution of the soil. Although observed as early
as 1824 by Brandes, and again in 1859 by A. Müller, this reaction is
not mentioned in text-books and attracted no attention as a source of
naturally occurring alkali carbonates which in the past have formed
the basis of extensive commerce from the Orient, until in 1888, the
writer together with Weber and later with Jaffa, investigated it
quantitatively.[171] It was found that up to .75 grms. per liter, the
entire amount of sodic sulfate present in solution is transformed into
carbonate in presence of calcic carbonate, by a current of carbonic
dioxid; but the amount so transformed does not continue to increase
beyond about 4 grams per liter. A corresponding amount of calcic
sulfate is formed. In the case of potassic sulfate, the transformation
also occurs, proportionally to the molecular weight. This relation is
shown in the subjoined diagram, which also shows in the curves on the
left, the residual alkalinity left after evaporation and drying the
residue at 100° C.
[171] Proc. Am. Soc. Agr. Sci., 1888; ibid., 1890; Rep. Cal. Expt.
Sta., 1890, p. 100; Ber. Berlin, Chem. Ges., 1893; Am. Jour. Sci.,
August 1896.
[Illustration: FIG. 69.—Progressive Transformation of Alkali Sulfates
into Carbonates. (The figures along upper line represent tenths of one
per cent.)]
The corresponding reaction occurs also, of course, between sodium
chlorid and calcium carbonate, but not to the same extent, because
unlike the difficultly soluble gypsum, the reaction product is the very
soluble calcium chlorid, the presence of which in the solution limits
the reaction much sooner than when most of the decomposition product
is thrown down in the solid state. The calcium chlorid not uncommonly
found in some alkali regions is undoubtedly the product of the above
reaction.
As the saline solutions in the soil are mostly quite dilute, and
calcic carbonate is always present, it follows that whenever under the
influences which favor the oxidation of organic matter in the soil,
and the activity of the plant roots, carbonic gas is formed somewhat
copiously, alkali sulfates and chlorids present may be partially or
wholly transformed into carbonates within the soil. As a matter of
fact, it is found that this transformation occurs most readily in the
moister portions of the soil and subsoil, and _invariably so when an
alkali soil is “swamped” by excessive irrigation or rise of bottom
water_; while the reaction is again reversed whenever free access of
air reduces the carbonic dioxid below a certain point. It thus becomes
intelligible why in the diagrams showing the distribution of the salts
(this chapter pp. 431 and 432), we always find the sodic carbonate
relatively _decreasing_ as the surface is approached.
Thus, also, is explained the fact that sodium carbonate is formed more
abundantly toward the center of the root system of alkali plants, such
as the greasewood, beneath which the soil is always more abundantly
charged with “black alkali” than is the surrounding earth.
Good aeration of the soil mass, then, is essential in maintaining the
neutralization of the “black alkali” soils brought about by the use of
gypsum (land plaster).
_Inverse Ratios of Alkali Carbonates and Sulfates._—According to the
above considerations, it is not surprising that we should often find
an apparent inverse ratio between the alkali sulfates and carbonates
in soils so closely adjacent that their salts must be presumed to be
similar in composition. A striking example is shown in fig. 70, in
which this inverse ratio becomes apparent four times in succession in
one and the same soil profile. While this inference is plain on the
face of the diagram, it is not quite easy to explain in detail how
this alternation came about from the condition observed two months
previously. Most probably it was caused by corresponding alternations
of weather, in which short, warm spring showers alternated with
similarly brief periods of drying north winds; the latter causing a
reversal of the formation of sodic carbonate that had been induced by
the former.
[Illustration: FIG. 70.—Amounts and Composition of Alkali Salts at
various depths in partly reclaimed Alkali Land. Tulare Experiment
Substation, California.]
_Exceptional Conditions._—While the phenomena of alkali lands as
outlined above probably represent the vastly predominant conditions
on level lands, yet there are exceptions due to surface conformation,
and the local existence of sources of alkali salts outside of the soil
itself. Such is the case where salts ooze out of strata cropping out on
hillsides, as at some points in the San Joaquin Valley in California,
and in parts of New Mexico, Colorado and Wyoming; also where, as in
the Hungarian plain, saline clays underlie within reach of surface
evaporation.
Again, it not infrequently happens that in sloping valleys or basins,
where the central (lowest) portion receives the salts leached out of
the soils of the adjacent slopes, we find belts of greater or less
width in which the alkali impregnation may reach to the depth of
ten or twelve feet, usually within more or less definite layers of
calcareous hardpan, likewise the outcome of the leaching of the valley
slopes. Such areas, however, are usually quite limited, and are at
present scarcely reclaimable without excessive expenditure; the more
as they are often underlaid by saline bottom water. In these cases
the predominant saline ingredient is usually common salt, as might be
expected and as is exemplified in the Great Salt Lake of Utah, in the
Antelope and Perris Valleys, and in Salton basin in California; in
the Yellowstone valley near Billings, Mont.[172] in the Aralo-Caspian
desert, and at many other points.
[172] Farmer’s Bull. No. 88, U. S. Dept. Agr., 1899.
_Conclusions._—Summing up the conclusions from the foregoing facts and
considerations, we find that—
(1) The amount of soluble salts in alkali lands is usually limited;
they are not ordinarily supplied in indefinite quantities from the
bottom-water below. These salts have mostly been formed by weathering
in the soil-layer itself.
(2) The salts move up and down within the upper four or five feet
of the soil and subsoil, following the movement of the moisture;
descending in the rainy season to the limit of the annual moistening
as a maximum, and then reascending or not, according as surface
evaporation may demand. At the end of the dry season, in untilled
irrigated land, practically the entire mass of salts may be within six
or eight inches of the surface.
(3) The direct injury to vegetation[173] is caused largely within a
few inches of the surface, by the corrosion of the bark, usually near
the root crown. This corrosion is strongest when carbonate of soda
(salsoda) forms a large proportion of the salts; the soda then also
dissolves the vegetable mold and causes blackish spots in the soil,
popularly known as black alkali.
[173] For a general statement and discussion of the physiological
effects of saline solutions on plants, see chapter 26.
(4) The injury caused by carbonate of soda is aggravated by its action
in puddling the soil so as to cause it to lose its crumbly or flaky
condition, rendering it almost or quite untillable and impervious. It
also tends to form in the depths of the soil-layer a tough, impervious
hardpan, which yields neither to plow, pick, nor crowbar. Its presence
is easily ascertained by means of a pointed steel sounding-rod.
(5) While alkali lands share with other soils of the arid region the
advantage of unusually high percentages of plant-food in the insoluble
form, they also contain, alongside of the noxious salts, considerable
amounts of water-soluble plant-food. When, therefore, the action of the
noxious salts is done away with, they should be profusely and lastingly
productive; particularly as they are always naturally somewhat moist
in consequence of the attraction of moisture by the salts, and are
therefore less liable to injury from drought than the same soils when
free from alkali.