Chapter XXVI The Vegetation of Saline and Alkali Lands
Marine Saline Lands.—While the saline alluvial lands of the sea-coast differ both in their mode of origin and in their nature from the alkali soils or “terrestrial saline lands,” as they have been called in Europe, their vegetation has in many respects a common character. Not only is there much similarity, sometimes even identity, in the kinds of plants inhabiting these lands, but their saline ingredients induce certain changes of form and structure in plants not properly “saline” but more or less tolerant of soluble salts, by which the saline or alkali character of the lands may be recognized.
Just as in the case of lime we must distinguish between the plants definitely repelled by a large amount of this substance in the soil (calcifuge), while others prefer the soils in which lime is abundant (calciphile), and still others appear to be indifferent to its presence and are governed in their habitat by the physical conditions presented: so in the case of saline lands the salts may attract or repel certain plants. The latter class is much the largest; while there is also a number of plants which are more or less indifferent to the presence of salts, provided these be not in very great excess. Such plants constitute the next-largest class; while those attracted by salts, and whose welfare is conditioned upon their presence, are comparatively few in number, and still fewer among them are of economic importance. Hence the soluble salts have largely a negative importance for agriculture; the question usually being how to utilize the land until the undesirable surplus of salts can be got rid of, partially or wholly, as the case may be; the former usually in seashore lands, the latter in the alkali lands proper; in which a small remnant, not sufficient to injure crop plants, is usually desirable (see chap. 23, p. 462).
General Character of Saline Vegetation.—Those familiar with seashore marshes cannot fail to note the fleshiness and succulence of the characteristic plants. This “incrassation” belongs not only to the saline flora proper, but is acquired to a greater or less degree when plants not ordinarily at home on saline ground are transferred to it artificially, or by saline overflows; while at the same time the leaves usually become smaller, and the growth more compact. Correspondingly, when saline plants are transferred to non-saline ground, the leaves generally become thinner and larger, and the growth more slender. The well-known “Russian thistle” is a case in point, as is also its close relative, the soda saltwort (Salsola soda); although the latter does not often venture as far from the saline lands as does the former (Salsola kali tragus), which now seems to have become a world-wide weed, with only a shade of preference for alkali lands.
Structural and Functional Differences Caused by Saline Solutions.—It has been definitely shown by the investigations of Schimper, Brick, Hoffmann, Lesage, Rosenberg and others, that the peculiarities or changes of structure brought about by saline solutions are essentially those pertaining to xerophile (drought-enduring) vegetation; which in general tend to the diminution of evaporation from the plant surfaces. It may be said, roughly speaking, that the absorption of water by the roots begins to diminish so soon as the concentration of the saline solution approaches or exceeds one-half of one per cent; while when it rises as high as three per cent, water-absorption by the roots ceases even in the wettest soils, and the plant suffers from drought quite as much as from any directly injurious effects of the salts. Different plants of course differ in the measure of concentration which brings about these phenomena, which vary also with the character of the soluble salts. It is stated that injurious or useless salts like common salt act at lower concentrations than e. g., saltpeter, which is useful. The difference in external structure are: diminution of the size of leaves, assumption of cylindrical or spinous forms, sinking-in of the breathing pores below the outer surface, dense hairy covering, resinous exudations, etc. Internally we find that xerophile plants have developed on their upper or outer leaf-surfaces instead of one, several layers of “palisade” (long and erect, closely-packed) cells, through which transpiration is extremely slow, as is also the transmission of heat. When salt-tolerant plants are grown on saline soils, their palisade cells are relatively lengthened.
Coincident with these external means for the retardation of evaporation, the leaves of xerophiles are frequently supplied with special water-storage cells, which supply moisture for the physiological processes when the root supply falls short. The cactus tribe and similar-looking plants are examples of the latter provision, which causes even animals suffering from thirst to resort to them, although they eschew the saline vegetation.
Absorption of the Salts.—The true halophytes or exclusive salt plants, which refuse to grow on lands not containing a large proportions of salt, often absorb so much salt that on drying it blooms out on their surface; they usually have, even when green, a distinctly salty taste, and their ash is rich in chlorids, specially of sodium. Such is the case of the samphire, common in saline marshes everywhere. The total ash is usually very high, often varying with the salinity of the water or soil in which they have grown. Thus the salt-content of the ash of samphire may vary by several per cent. In other cases, as in that of one of the Australian saltbushes investigated at the California station, neither the ash content nor the composition of the ash varies materially whether the plant be grown on strong alkali land, or on uplands whose total saline content does not exceed (in four feet depth).015% or 2500 pounds per acre.
The following table gives the composition of the ash of this saltbush alongside of that of two other prominent alkali-plants of the same relationship, occurring, one in the San Joaquin valley of California, in strongly saline lands, the other in the Great Basin region of the interior, on lands strongly impregnated with carbonate of soda. All these, it will be seen, take up very large amounts of sodium salts, notably the chlorid; the Australian plant most so, the “greasewood” of the Great Basin least so; a large proportion of the alkali salts being evidently, in the latter case, contained in the form of organic salts, which in the ash become carbonates.
ANALYSES
(A) = Australian Saltbush, Atriplex semibaccata.†
(B) = Bushy Samphire, Allenrolfea occidentalis.†
(C) = Greasewood, Sarcobatus vermiculatus.†
(D) = Saltgrass, Distichlis spicata.‡
(E) = Tussock grass, Sporobolus airodies.‡
(F) = Prickly Pear, Opuntia macrocentra.‡
OF ASHES OF SALINE AND
ALKALI PLANTS.
| (A) | ( B) | (C) | (D) | (E) | (F) | |
|---|---|---|---|---|---|---|
| Ash, air-dried plant, %. | 19.37 | 12.03 | 13.81 | 11.61 | 7.99 | 24.18 |
| Potash (K₂O) | 11.42 | 18.53 | 30.11 | 3.30 | 5.78 | 1.61 |
| Soda (Na₂O) | 35.39 | 39.45 | 32.58 | 2.38 | 5.15 | 2.76 |
| Lime (CaO) | 5.75 | 1.36 | 8.70 | 5.25 | 8.05 | 65.66 |
| Magnesia (MgO) | 3.23 | 1.09 | 1.09 | 2.95 | 4.15 | 26.70 |
| Br. ox. of Manganese (Mn₃O₄) | .22 | .16 | .25 | |||
| Peroxid of Iron (Fe₂O₃) | 3.33 | 7.06 | not det’d. | 2.22 | 2.39 | 1.19 |
| Alumina (Al₂O₃) | ||||||
| Silica | 16.24 | 11.81 | 4.00 | 78.73 | 66.79 | .81 |
| Phosphoric acid (P₂O₅) | 2.80 | 3.51 | 5.60 | .83 | 1.25 | .47 |
| Sulfuric acid (SO₃) | 2.64 | 4.93 | 5.90 | 3.20 | 4.52 | .64 |
| Chlorin, percent | 24.33 | 15.30 | 11.00 | 1.40 | 2.13 | .21 |
| Totals | 105.35 | 103.04 | 99.79 | 100.3 | 100.46 | 100.05 |
| Less excess, O: Cl | 5.35 | 3.25 | 2.50 | .31 | .46 | .05 |
| True totals | 100.00 | 99.79 | 97.29 | 100.00 | 100.00 | 100.00 |
(G) = Shad scale, Atriplex canescens.‡
(H) = Alfalfa Hay. (Cal.)†
(I) = Timothy Hay.
OF FORAGE CROPS.
| (G) | ( H) | (I) | |
|---|---|---|---|
| Ash, air-dried plant, %. | 4.23 | 9.85 | 6.15 |
| Potash (K₂O) | 25.17 | 43.72 | 28.80 |
| Soda (Na₂O) | 6.23 | 4.48 | 2.70 |
| Lime (CaO) | 25.97 | 20.51 | 9.83 |
| Magnesia (MgO) | 16.63 | 2.56 | 3.60 |
| Br. ox. of Manganese (Mn₃O₄) | .51 | ||
| Peroxid of Iron (Fe₂O₃) | 5.89 | 2.95 | |
| Alumina (Al₂O₃) | |||
| Silica | 11.94 | 5.87 | 35.00 |
| Phosphoric acid (P₂O₅) | 3.11 | 5.00 | 10.80 |
| Sulfuric acid (SO₃) | 4.93 | 6.92 | 3.90 |
| Chlorin, percent | 2.07 | 10.25 | 5.00 |
| Totals | 100.45 | 102.26 | 99.70 |
| Less excess, O: Cl | .45 | 22.6 | 1.13 |
| True totals | 100.00 | 100.00 | 98.57 |
| † Jaffa, Cal. St’n. Rept. 1894-95, p. 169. | |||
| ‡ Goss, New Mex. St’n. Bull. No. 44; recalculated. | |||
It will be noted that the saltbush hay contains nearly one-fifth of its (air-dry) weight of ash, of which nearly 40% is common salt. It therefore has a distinctly salty taste, and is always moist to the touch, containing-ordinarily over 15% of moisture. It is therefore much liked by stock when fed intermixed with other hay, and thus supplies all the salt needed by cattle. The greasewood is much less liked by stock, and bushy samphire is wholly rejected by them. Comparing with these fleshy plants the ash of the two grasses, the first a world-wide “salt grass,” the other a common grass of the American arid region, we note that not only do they contain much less soluble ash than the saltbushes, but especially much smaller amounts of sodium salts; proving that even when growing in company with the saltbushes on strongly impregnated land, they can repel from absorption these to them useless or injurious salts. But in the case of the “shad scale,” also a “saltbush” of the Great Basin, the ash-content is remarkably low—only about one-fifth of that of its Australian relative—and it differs widely from the latter in having but a very low proportion of soda, and a very high one of lime and potash, approaching in these respects to our usual forage crops; and being also fairly rich in nitrogen, it forms acceptable browsing when other pasture plants are scarce. It therefore does not exert the laxative action produced by the exclusive feeding on the more saline herbages.
The exceptionally high ash-content of the cactus or prickly pear, also given in the table, arises, it will be noted, not from the soluble salts but from the absorption of extraordinarily high proportions of lime and magnesia. Owing probably to the latter substance, and also the oxalate form in which lime is usually found in the cactus tribe, this plant when used as forage is also somewhat laxative.
Altogether, this table offers remarkable examples of wide differences in the kind and amount of ash ingredients absorbed by plants growing upon similar soils and under identical climatic conditions; indicating a selective power which no merely physical theory of soil-action in plant growth can explain.
Injury to Plants from the Various Salts.—The early observers, especially Contejean, were predisposed from their observations of lime on vegetation to ascribe the action of salt upon marine vegetation to the sodium component. But the wide differences in the effects of different sodium compounds, notably of common salt and Glaubers salt, led some to the conclusion that the acidic ingredients are the chief determining factors. Moreover, it was soon found that a single salt is more injurious than a mixture of several, such as sea water. This also led to the inference that the varying degree of dissociation of these salts essentially influences the effects.
Kearney and Cameron have investigated these relations,201 and have by artificial cultures in solutions of varying concentration and composition studied the behavior of plant roots and the limits of their endurance. They found for the several salts occurring in alkali soils, taken separately, the following figures, in 100,000 parts of water:
| Magnesium | sulfate | 7 |
| “ | chlorid | 12 |
| Sodium | carbonate | 26 |
| “ | sulfate | 53 |
| “ | chlorid | 116 |
| “ | bicarbonate | 167 |
| Calcium | chlorid | 1,377 |
It will be noted that in many respects the results given in this table stand in marked contrast to the facts observed in alkali lands everywhere; and therefore while interesting physiologically, are not directly applicable to practice. Magnesium sulfate, which according to this table is the most injurious of all, is a common ingredient of alkali lands from Wyoming to New Mexico, as also is sodium sulfate; yet there, as well as in the Musselshell valley in Montana, and at many other points, it shows no specially deleterious action either upon native or cultivated plants, and in Europe as well as in New England the mineral kieserite is freely used as a fertilizer at many points. That sodium sulfate should be twice as harmful as sodium chlorid or common salt, and half as harmful as the carbonate or black alkali, is again wholly contrary to actual experience, which as shown elsewhere in this chapter, indicates that the majority of plants will tolerate between three and four times as much of sodium sulfate as of common salt; while the ratio of tolerance as against the carbonate seems sometimes to rise as high as ten to one.
It is clearly evident, however, that it is the metallic or basic ingredient that in the main determines the toxicity of these salts. The universal presence of lime in some form in all alkali lands doubtless explains the discrepancies mentioned, since lime is especially potent in counteracting the injurious effects; thus throwing additional light upon the importance of the lime-content of alkali soils proper, and also upon the causes of the narrow limitations of the littoral (marine saline) flora; inasmuch as, unlike alkali soils, marine alluvial lands are by no means always calcareous. Cameron goes so far as to attribute the favorable effects of gypsum upon black alkali not so much to the conversion of the latter into neutral sulfate, as to the effect of gypsum solution in counteracting the saline effects. This interpretation, however, seems rather far-fetched, since there can be no question about the double decomposition of gypsum with carbonate of soda; or the intense injuriousness of carbonate of soda in the actual corrosion of vegetable tissues. The corresponding protective influence of various salts, more especially of those of lime, against the injurious effects of pure common salt on marine animals, has already been mentioned (chapter 20, page 380), and later investigations by Osterhout on marine algæ, show the same relation to hold true for them also.
Reclamation of Marine Saline Lands for Culture.—The reclamation of sea-coast lands and marshes for agricultural use is based in general upon the same methods as those already outlined for alkali lands in chapter 20; except that in this case no chemical neutralization is possible, since common salt cannot be changed by any practically feasible means. It must be removed by leaching, and this, in the humid countries in which such reclamations have chiefly been made, is usually done by the agency of rains, aided by ditching. The “polder” lands thus reclaimed along the shores of the North Sea, from Belgium to Prussia, are especially esteemed for their productiveness, doubtless owing to the alluvium of the numerous rivers tributary to that sea, which is distributed along its shores and in the numerous inlets and bays. The tides are of course excluded by dikes provided with gates opening outward, so as to permit of the outflow of rain- or irrigation-water used for leaching purposes.
Out of reach of stream alluvium no exceptional fertility is to be expected of seashore lands, which then commonly assume the form of sand dunes or bars, incapable of nourishing any cultural vegetation. Of the latter, the groups listed below as tolerant of alkali salts, may also be considered with reference to reclaimed seashore lands; the first cereal to succeed being usually barley, the first root crop, beets. Asparagus is also available while salt is being leached out.
The Vegetation of Alkali Lands
The general character of alkali-land vegetation is not unlike that of saline seashore lands; some species of plants are common to both, but the alkali lands harbor a much greater variety of plants, owing to the differences in climates and soils as well as to the nature of the impregnating salts. Moreover, owing to the very causes which underlie the presence of these salts, viz, aridity, the xerophile or dry-land character of the alkali-land flora is much more pronounced than that of the saline seashore vegetation. In view of the very complex conditions, the discussion of the alkali-flora is of necessity much more complex than that of the marine group; and the data for its full elucidation with respect to the nature of the soils and salts are as yet very incomplete.
Reclaimable and Irreclaimable Alkali Lands as Distinguished by Their Natural Vegetation
While, as shown above (chapter 20), the adaptation or non-adaptation of particular alkali lands to certain cultures may be determined by sampling the soil and subjecting the leachings to chemical analysis, it is obviously desirable that some other means, if possible available to the farmer himself, should be found to determine the reclaimability and adaptation of such lands for general or special cultures.
In alkali lands, as in others, the natural plant-growth affords such means, both as regards the quality and quantity of the saline ingredients. The most superficial observation shows that certain plants indicate extremely strong alkali lands where they occupy the ground alone; others indicate pre-eminently the presence of common salt; the presence or absence of still others form definite or probable indications of reclaimability or non-reclaimability. Many such characteristic plants are well known to and readily recognized by the farmers of the alkali districts. “Alkali weeds” are commonly spoken of almost everywhere; but the meaning of this term—i. e., the kind of plant designated thereby—varies materially from place to place, according to climate as well as the quality of the soil. It is obvious that if these characteristic plants were definitely observed, described and named, while also ascertaining the amount and kind of alkali they indicate as existing in the land, lists could be formed for the several regions, which would indicate, in a manner intelligible to the farmer himself, the kind and degree of impregnation with which he would have to deal in the reclamation work; thus enabling him to go to work on the basis of his own judgment, without previous chemical examination.
A study of the lands of California having this purpose in view, was undertaken in the years 1898 and 1899 by the California Station; but lack of funds prevented its prosecution beyond the ascertainment of those plants the abundant occurrence of which prove the land to be irreclaimable without the use of the universal remedy, viz, underdrainage, which on the large scale is usually beyond the means of the land-seeker. The botanical field work and collection of soil samples was carried out by Mr. Jos. Burtt Davy; the chemical work, as heretofore, being done by Dr. R. H. Loughridge. The results here reported are therefore essentially their joint work. It is hoped that in the future, a more comprehensive study and close comparison of the native vegetation with the chemical determination of the quality and kind of alkali corresponding to certain plants, or groups of plants, naturally occurring on the land, may enable us to come to a sufficiently close estimate of the nature and capabilities of the latter from the native vegetation alone, or with the aid of test plants purposely grown, for the farmers’ purposes.
Plants Indicating Irreclaimable Lands.—The plants herein-after mentioned and figured are, then, to be understood as indicating, whenever they occupy the ground as an abundant and luxuriant growth, that such land is irreclaimable for ordinary crops, unless underdrained for the purpose of washing out surplus salts. The occurrence merely of scattered, more or less stunted individuals of these plants, while a sure indication of the presence of alkali salts, does not necessarily show that the land is irreclaimable.
The plants which may best serve as such indicators in California are the following:
Tussock-grass (Sporobolus airoides Torr.), Fig. 82.
Bushy Samphire (Allenrolfea occidentalis [Wats.] Ktze.), Fig. 83.
Dwarf Samphire (Salicornia subterminalis Parish, and other species), Fig. 84.
Saltwort (Suaeda torreyana Wats., and S. suffrutescens, Wats.), Fig. 85.
Greasewood (Sarcobatus vermiculatus [Hook.] Torr.), Fig. 86.
Alkali-heath (Frankenia grandifolia campestris Gray), Fig. 87.
Cressa (Cressa truxillensis Choisy), Fig. 88, perhaps identical with C. cretica auct.
Saltgrass (Distichlis spicata), Fig. 89.
Tussock-grass (Sporobolus airoides, Torr.); Fig. 82.
(“Bunch grass” of New Mexico).
The three sets of Tussock-grass soil which have been analyzed show that the total amount of all salts present is in no case less than 49,000 pounds per acre, to a depth of four feet; and that it sometimes reaches the extraordinarily high figure of 499,000 pounds. Of these amounts the neutral salts (Glauber’s salt and common salt) are usually in the heaviest proportion (Glauber’s salt, 19,600 to 323,000 pounds per acre; common salt, 3,500 to 172,800); the corrosive salsoda varying from 3,000 to 44,000 pounds.—Tussock-grass apparently cannot persist in ground which is periodically flooded. It is of special importance because it is an acceptable forage for stock.
Tussock-grass is a prevalent alkali-indicator in the hot, arid portions of the interior, from the upper San Joaquin Valley, the Mojave desert, and southward; also through southern Nevada and Utah as far east as Kansas and Nebraska. In the San Joaquin Valley it has not been found farther north than the Tulare plains, although east of Reno it occurs near Reno. Coville observes that in the Death Valley region “it is confined principally to altitudes below 1,000 meters” (3,280 feet). Hillman, however, reports it from near Reno, Nevada, at an altitude which cannot be much less than 4,500 feet.
The tussocks formed by this grass, which are unfortunately not shown in the figure, sometimes appear as veritable little grass trees, and when denuded by the browsing of cattle seem like trunks 18 and 20 inches high. It is therefore very easily recognized; but it should be noted that in view of the extraordinary range of its tolerance, shown above, its scattered occurrence does not necessarily indicate irreclaimable land.
Bushy samphire.
(Allenrolfea occidentalis [Wats.] G. Ktze.) Fig. 83..
This plant is locally called greasewood, but as this name is much more commonly used for Sarcobatus vermiculatus, it seems best to call Allenrolfea “bushy samphire,” as it closely resembles the true samphire (Salicornia).
Bushy Samphire usually grows in low sinks, in clay soil which in winter is excessively wet, and in summer becomes a “dry bog.” Wherever the plant grows luxuriantly the salt content is invariably high, the total salts varying from 327,000 pounds per acre, to a depth of three feet, to 494,520 pounds in four feet. The salts consist mainly of Glauber’s and common salts (a maximum of about 275,000 pounds each); salsoda varies from 2,360 to 4,800 pounds per acre. The percentage of common salt and total salts is higher than for any other plant investigated, and the content of Glauber’s salt is also excessive. The areas over which this plant grows must therefore be considered among the most hopeless of alkali lands, for although its salts are “white,” submergence during winter precludes the growth of Australian saltbushes. Full underdrainage alone could reclaim the soil-areas it occupies. Bushy Samphire is common on low-lying alkali lands in the upper San Joaquin Valley, California, and extends northward along the eastern slopes of the Coast Range to Suisun Bay. It is also abundant in the Death Valley region, apparently overlapping the southward range of the Sarcobatus, the greasewood properly so-called.
Dwarf samphire
(Salicornia subterminalis,
Parish, and other species of the interior); Fig. 84.
A. Much-branched form.
B. Slender form.
C. Flower with the perianth removed showing the simple pistil and the two stamens.
D. Portion of flowering spike, showing two joints. The flowers are impressed in the joints in opposite clusters of three. In each cluster the middle flower stands slightly above the two laterals as shown in the lower joint.
The three or four species of Dwarf Samphire which grow in the interior valleys of the State are not usually very abundant, save locally. Wherever the species do occur, however, they may be considered as indicating excessively saline soils. Dwarf Samphire soil has shown a total salt content of 441,880 pounds per acre in a depth of four feet. The neutral Glauber’s salt amounts to 314,000 pounds, almost as much as in Tussock-grass soil; common salt up to 125,640 pounds while the salsoda varies from 2,200 to 12,000. We may consider the plant as indicative of almost the highest percentage of common salt, Glauber’s salt and total salts. Like the preceding species it indicates land strongly charged with salts, more especially common salt, and susceptible to cultivation only after reclamation by underdrainage.
Salicornia subterminalis, S. herbacea (L.), S. mucronata, and another species, all occurring inland, differ materially in habit and botanical characters from the one so conspicuous in submerged salt marshes along the seashore; but all alike indicate strongly saline soils, reclaimable only by thorough drainage.
Saltwort
(Suaeda torreyana, Wats.,
S. suffrutescens, Wats.,
and perhaps one other species); Fig. 85.
Samples of saltwort soil from Bakersfield and Byron Springs, California, taken to a depth of one foot and three feet respectively, show that this plant grows luxuriantly in a soil containing 130,000 pounds of total salts per acre in the first foot, and with 10,480 pounds of the noxious salsoda, and 39,760 pounds of common salt in three feet; while only a sparse growth is found on soils containing only 3,700 pounds of salts in three feet. It thus appears to indicate a lower percentage of salsoda than does Greasewood, but a higher percentage than Bushy Samphire. Further investigation is necessary to determine the exact relation of the different salts to the growth of the plant, and as to whether carbonates occur in large quantity; but enough data have been gathered to show that a luxuriant growth of Suaeda torreyana indicates a soil reclaimable only by thorough-drainage.
Suaeda torreyana occurs on low alkali lands throughout the State of California, from San Bernardino to Honey Lake, in the desert sinks, and in the Great Valley, in appropriate locations. Sometimes it is replaced by S. suffrutescens and perhaps other species, but all the saltworts appear to grow in similar habitats, and it is probable that the soil-conditions are practically the same for all these species. They indicate land too heavily impregnated for the growth of ordinary crops, but which will perhaps allow the Australian saltbush to succeed.
This, the true Greasewood of the desert region east of the Sierra Nevada, and not either of the plants known under that name in the San Joaquin Valley and in Southern California, invariably indicates a heavy impregnation of the land with black alkali or carbonate of soda. Since, as before stated, black alkali is most likely to occur in low ground, we frequently find the true greasewood forming bright green patches in the swales, and on the benches of periodic streams, as well as on the borders of alkali ponds or lakes. Stock unaccustomed to it will frequently go to these patches on a run, only to turn away badly disappointed after taking a few bites, the plant being both bitter and salty.
A. Appearance of a branch when not in blossom.
B. Spiny-branchlet from the same.
C. Branchlet bearing cones of male flowers.
D. Cone of male flowers, enlarged.
E. Branch bearing fruits.
F. Cluster of fruits, enlarged.
G. Vertical section through a fruit, showing the seed with its curved embryo, (enlarged).
Where a luxuriant growth of this plant is found, the soil may contain from 38,000 to 117,000 pounds of total salts per acre, of which sometimes nearly half is carbonate of soda; the content of common salt is usually low, and Glauber’s salt or sulfate of soda, sometimes with considerable proportion of epsom salt, forms a variable proportion of the total.
Greasewood is distinctly a plant of the Great Basin, only reaching California in the adjacent counties of Lassen, Alpine, Mono, and northern Inyo. It is very abundant on the lower levels of Honey Lake valley, Cal.
The Sarcobatus is chiefly found on silty or sandy soils of good native fertility (see page 445, chapter 22), so that when its excess of salsoda is neutralized by means of gypsum, the land becomes very productive. Unfortunately the cost of the amount of gypsum required to render such soils adapted to the tolerance of most culture plants is often prohibitive; but where the correction of only small spots is called for, the “white alkali” resulting from the gypsum treatment would be tolerated by many culture plants.
Alkali-heath
(Frankenia grandifolia campestris Gray);
Fig. 87.
Alkali-heath is perhaps the most widely distributed of any of the California alkali plants. Its perennial, deep-rooting habit of growth, and flexible, somewhat wiry rootstock, which enables it to persist even in cultivated ground, render it a valuable plant as an alkali indicator. The salt-content where Alkali-heath grows luxuriantly is invariably high, ranging from 64,000 to 282,000 pounds per acre; salsoda varies from 680 to 19,590 pounds; common salt ranges from 5,000 to 10,000 pounds. Such soils would not be benefited by the application of gypsum, as the salts are already largely in the neutral state. Of useful plants only Saltbushes and Tussock-grass are likely to flourish in such lands, when not too wet.
While Alkali-heath is thus one of the most alkali-tolerant plants, it is at the same time capable of growth with a minimum of salts (total salts 3,700 pounds, salsoda 680 pounds). Where only a sparse growth of this plant occurs, therefore, the land should not be condemned until a chemical examination of the soil has been made.
Alkali-heath is found on soils of very varying physical texture and degrees of moisture; while on soils of uniform texture and moisture-conditions, but differing in chemical composition, it varies with the varying salt-content.
It has been found that Australian saltbush (Atriplex semibaccata) can be successfully grown on the “goose-lands,” of the Sacramento Valley, on soil producing a medium crop of Alkali-heath; it remains to be shown whether it will do equally well on soils producing a dense and luxuriant growth of the same.
Alkali-heath is widely distributed throughout the interior valleys of California; a closely related form grows in the salt-marshes of the sea-coast.
Cressa
(Cressa cretica truxillensis Choisy);
Fig. 88.
Cressa soils show a low percentage of the noxious salsoda, but comparatively heavy total salts (161,000 to 282,000 pounds per acre.) Common salt varies from 5,760 to 20,840 pounds per acre in four feet. The maximum is lower than in the case of Alkali-heath, but Cressa seems to be much more closely restricted to strong alkali than does the former species. Cressa appears to be as widely distributed through the interior valleys of California as Alkali-heath. The Cressa is a cosmopolitan plant, occurring, as its name indicates, on the Ionian Islands, as well as in North Africa, Syria, and other arid countries of the world.
Saltgrass, Distichlis spicata.—This grass is of world-wide distribution, and always indicates a sensible content of soluble salts, without apparently any special preference for either of the three most commonly occurring ones. Its maximum tolerance, as will be seen by the preceding table, is very high, yet at the same time it will grow luxuriantly on lands containing so little that other saline plants like the samphires, saltwort or greasewood will refuse to grow. On the shores of Honey Lake, California, it may often be seen incrusted with the salts of the water concentrated by a long season of drought, yet maintaining life, though somewhat stunted. On lands lightly impregnated, stock will often eat it quite freely, so that it has been mistaken for Bermuda grass, to which its habit and foliage bears some resemblance. But Bermuda grass, while not as sensitive to alkali as most forage grasses, will probably not bear much over 12,000 pounds per acre.
The mere presence of the salt grass cannot therefore be taken as a definite indication of anything more than that there is an unusual amount of salts in the soil; whether or not there is more than will be tolerated by the ordinary culture-plants, must be judged either from the accompanying plants, or by experiment or analysis.
Relative Tolerance of the Different Species.—The following table shows in systematic order the tolerance of the several plants discussed above, for the different salts, so far as the data available permit. The column marked optimum shows under what proportions of salts the plants grew in about equal luxuriance, therefore under, apparently, the most favorable conditions. Both above and below the proportions mentioned in that column, the luxuriance (size) and (usually) the abundance of the plants was less; showing that while excessive amounts of salts depressed their welfare, yet they also suffered when the proportions dropped below a certain point. Whether this was partly or wholly the result of competition with other plants, is an unsettled question.
TABLE SHOWING MAXIMUM, OPTIMUM, AND
MINIMUM OF SALTS TOLERATED BY EACH OF
THE SEVERAL ALKALI PLANTS.
| Pounds Per Acre in feet. | |||
|---|---|---|---|
| Optimum. | Maximum. | Minimum. | |
| Total Salts. | |||
| Bushy Samphire | 494,320 | 494,520 | 135,060 |
| Dwarf Samphires | 441,880 | 441,880 | 441,880 |
| Alkali-heath | 281,960 | 499,040 | 3,720 |
| 64,300 | |||
| Cressa | 281,960 | 281,960 | 161,160 |
| Saltworts | 130,000 | 153,020 | 3,720 |
| Greasewood | 58,560 | 58,560 | 2,400 |
| Tussock-grass | 49,000 | 499,040 | 49,000 |
| Carbonate (Salsoda). | |||
| Tussock-grass | 23,000 | 44,460 | 3,040 |
| Alkali-heath | 20219,590 | 19,590 | 680 |
| 680 | |||
| Greasewood | 18,720 | 18,720 | 1,280 |
| Dwarf Samphires | 12,120 | 12,120 | 2,200 |
| Saltworts | 10,480 | 12,120 | 1,120 |
| Cressa | 5,440 | 5,440 | 680 |
| Bushy Samphire | 4,800 | 4,800 | 1,500 |
| Chloride (Common Salt). | |||
| Bushy Samphire | 212,080 | 275,160 | 56,800 |
| Dwarf Samphires | 125,640 | 125,640 | 125,640 |
| Saltworts | 39,760 | 52,900 | 1,040 |
| Cressa | 20,840 | 20,840 | 5,760 |
| Alkali-heath | 10,180 | 212,080 | 1,040 |
| 5,760 | |||
| Tussock-grass | 6,200 | 172,800 | 3,530 |
| Greasewood | 3,680 | 3,680 | 160 |
| Sulphates (Glauber’s salt). | |||
| Dwarf Samphires | 314,040 | 314,040 | 314,040 |
| Bushy Samphire | 277,640 | 277,640 | 50,080 |
| Cressa | 275,520 | 275,520 | 134,880 |
| Alkali-heath | 275,520 | 323,200 | 1,560 |
| 34,530 | |||
| Saltworts | 44,160 | 104,040 | 1,560 |
| Greasewood | 36,160 | 36,160 | 960 |
| Tussock Grass | 19,640 | 323,200 | 19,640 |