XXVI. THE VEGETATION OF SALINE AND ALKALI LANDS

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 OF ASHES OF SALINE AND ALKALI PLANTS.

(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.‡ ========================+======+======+======+======+======+====== | (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 | 2.22| 2.39| 1.19 Alumina (Al₂O₃) | | |det’d.| | | ------------------------+------+------+------+------+------+------ 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|100.31|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

[201] Report No. 71, U. S. Dep’t. of Agriculture, 1902.

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.

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.

GREASEWOOD (Sarcobatus vermiculatus) [Hook. Torr.]; FIG. 86.

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 [202]| { 19,590}| 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 -------------------------------+-----------+--------+--------

[202] This plant grows with equal luxuriance in soils containing only 680 pounds of carbonates.

APPENDICES.

APPENDIX A.

DIRECTIONS FOR TAKING SOIL SAMPLES. ISSUED BY THE CALIFORNIA EXPERIMENT STATION.

In taking soil specimens for examination by the Agricultural Experiment Station, the following directions should be carefully observed; always bearing in mind that the examination, and especially the analysis, of a soil is a long and tedious operation, which cannot be indefinitely repeated.

First.—Do not take samples at random from any points on the land, but consider what are the two or three chief varieties of soil which, with their intermixtures, make up the cultivable area, and carefully sample these, each separately; then, if necessary, sample your particular soil, noting its relation to these typical ones.

Second.—As a rule, and whenever possible, take specimens from spots that have not been cultivated, nor are otherwise likely to have been changed from their original condition of “virgin soils”—e.g., not from ground frequently trodden over, such as roadsides, cattle-paths, or small pastures, squirrel holes, stumps, or even the foot of trees, or spots that have been washed by rains or streams, so as to have experienced a notable change, and not be a fair representative of their kind.

Third.—Observe and record carefully the normal vegetation, trees, herbs, grass, etc., of the average virgin land; avoid spots showing unusual growth, whether in kind or in quality, as such are likely to have received some animal manure, or other outside addition.

Fourth.—Always take specimens from more than one spot judged to be a fair representative of the soil intended to be examined, as an additional guarantee of a fair average, and mix thoroughly the earth taken from the same depths.

Fifth.—After selecting a proper spot, pull up the plants growing on it, and sweep off the surface with a broom or brush to remove half-decayed vegetable matter not forming part of the soil as yet. Dig or bore a vertical hole, like a post-hole, and note at what depth a change of tint occurs. In the humid region, or in humid lowlands of the arid, this will usually happen at from six to nine inches from the surface, and a sample taken to that depth will constitute the “soil.”

In California and the arid region generally, very commonly no change of tint occurs within the first foot, sometimes not for several feet; hence, especially in sandy lands, the “soil” sample will usually be taken to that depth, so as to represent the average of the first foot from the surface down.

Samples taken merely from the surface, or from the bottom of a hole, have no definite meaning, and will not be examined or reported upon.

Place the “soil” sample upon a cloth (jute bagging should not be used for the purpose, as its fibres, dust, etc., become intermixed with the soil) or paper, break it up, mix thoroughly, and put at least a quart of it in a sack or package properly labeled, for examination.

This specimen will, ordinarily, constitute the “soil.” Should the change of color occur at a less depth than six inches, the fact should be noted, but the specimen taken to that depth nevertheless, since it is the least to which rational culture can be supposed to reach.

In the same way take a sample of each foot separately to a depth of at least three feet; preferably four or five, especially in the case of alkali soils, or suspected hardpan.

Sixth.—Whatever lies beneath the line of change, or below the minimum depth of six inches, will constitute the “subsoil.” But should the change of color occur at a greater depth than twelve inches, the “soil” specimen should nevertheless be taken to the depth of twelve inches only, which is the limit of ordinary tillage; then another specimen from that depth down to the line of change, and then the “subsoil” specimens beneath that line.

The depth down to which the last should be taken will depend on circumstances. It is always necessary to know what constitutes the foundation of a soil, down to the depth of three feet at least, since the question of drainage, resistance to drought, root-penetration, etc., will depend essentially upon the nature of the substratum. In the arid region, where roots frequently penetrate to depths of ten or twelve feet or even more, it is frequently necessary to at least probe the land to that depth or deeper. The specimens should be taken in other respects precisely like that of the surface soil, each to represent the average of not more than twelve inches. Those of the materials lying below the third foot from the surface may sometimes be taken at some ditch or other easily accessible point, and if possible should not be broken up like the other specimens.

If there is hardpan or heavy clay present, an unbroken lump of it should be sent, for much depends on its character.

Seventh.—When in the case of cultivated lands, it is desired to ascertain the cause of differences in the behavior or success of a crop on different portions of the same field or soil area, do not send only the soil which bears unsatisfactory growth, but also the one bearing normal, good growth, for comparison. In all such cases, try to ascertain by your own observations whether or not the fault is simply in the subsoil or substrata; in which case a sample of surface soil sent for examination would be of little use. In such examinations the soil probe will be of great service, and save much digging or boring.

Eighth.—Specimens of alkali or salty soils should preferably be taken towards the end of the dry season, when the surface layers will contain the largest amount of salts. A special sample of the first six inches should in that case be taken separately by means of a post-hole auger, and then, in a different spot close by, a hole four feet deep should be bored, and the earth from the entire four-foot column intimately mixed before the usual quart sample is taken. Samples of the plants growing on the land should in all cases be included in the package, as they indicate very closely the agricultural character of the land.

All samples taken while the land is wet should be air-dried before sending; in the case of alkali soils this is absolutely essential.

Ninth.—All peculiarities of the soil and subsoil, their behavior under tillage and cultivation in various crops, in wet and dry seasons, their location, position, “lay,” every circumstance, in fact, that can throw any light on their agricultural qualities or peculiarities, should be carefully noted, and the notes sent by mail. Without such notes, specimens cannot ordinarily be considered as justifying the amount of labor involved in their examination. Any fault found with the behavior of the land in cultivation or crop-bearing should be specially mentioned and described. The conditions governing crop-production are so complex that even with the fullest information and the most careful work, cases are found in which as yet the best experts will be at fault.

APPENDIX B.

SUMMARY DIRECTIONS FOR SOIL—EXAMINATION IN THE FIELD OR ON THE FARM.

While the general principles upon which the cultural value and adaptations of lands should be judged, have been given in the text of this volume, it seems advisable to summarize their practical application to land examination here, for convenient reference.

The directions given in Appendix A for the sampling of soils having been carried out, the samples so taken may be subjected to farther examination by any intelligent farmer to good purpose, and often with great saving of time and expense.

Spread the samples from the several depths in regular order upon a table or bench, and note the differences in color and texture apparent to the eye or touch, and whether they will or will not crush readily between the fingers, wet and dry. Whatever the fingers can do, can similarly be done by the harrow, cultivator, clod crusher or roller.

The tilling qualities of the surface soil and immediate subsoil are the first and most important matter to be ascertained; including especially their behavior to water. Place some air-dried lumps in a shallow dish with a little water; observe whether they take up the water quickly or slowly, and whether in so doing the lumps fall to pieces or retain their form. Slow penetration, and maintenance of form, will at once indicate a soil somewhat refractory and difficult to till; while if the water is taken up easily and the lump falls to pieces, the land is easily cultivated and will absorb the rainfall and irrigation water readily. The darkening of the tint on wetting will also give an approximate idea of its humus-content.

Then take a wetted lump and work it between the fingers and on the palm of the hand, until its “stickiness” or adhesiveness ceases to increase. This “hand test” is of first importance and in skillful hands will largely supersede the need of elaborate mechanical analysis. It will at once enable the operator to classify the soil as a light or heavy loam, clay loam or clay soil; it will show directly what will be the result of plowing the land when wet, the liability to the formation of a plowsole, and whether a single or a double team will generally be needed to cultivate it properly. Also whether stock can be allowed to pasture the land soon after rain. Comparison with the known land of neighbors will also thus become easy, and in a measure the crops best adapted to the physical qualities of the soil, subsoil and substrata, taking into account their respective depths, will at once be at least approximately determined. The presence of coarse and fine sand in greater or less amounts will also be thus readily ascertained, allowing estimates of the percolative properties; the latter can, of course, be more practically tested in the field, in the manner described in chapter 13, page 242.

A more definite estimate of the amount and kind of sand present in the soil materials can be obtained by washing the kneaded sample into a tumbler, and allowing a thin stream of water to flow into it from a faucet while gently stirring the turbid water. The clay, together with the finest silts, will thus be carried off over the rim of the glass, and sand of any desired degree of fineness, according to the strength of the stream of water used, will be left behind. The kind and amount of these sandy materials can then be estimated, or definitely ascertained by weighing or measuring.

This will, generally speaking, be as far as the uninstructed farmer can readily go; but these simple operations will give him an insight into the nature of his soil and subsoil that will enable him to avoid a great many costly mistakes.

RECOGNITION AND MEANING OF THE SEVERAL SOIL MINERALS.[203]

Those somewhat familiar with scientific methods and operations, and supplied with pocket lens or microscope, can profitably go much farther towards the definite ascertainment of the permanent cultural value of the land, by the study of the minerals of which the sand is composed, and which as a rule represent those from which the entire soil has been formed; therefore indicate in a general manner its chemical composition. Such examinations are specially feasible and important when soils are not far removed from their parent rocks, as in most of the arid region, and in the states north of the Ohio. In the Southwestern states, in the coastal plain of the Gulf of Mexico, the original soil minerals have usually been too far decomposed to admit of definite identification. Sand is there as a rule made up of quartz grains of many varieties, with only an occasional tourmaline and pyroxene.

[203] For more details see chapters 3 and 4.

Among the prominent soil minerals, quartz is almost always recognizable by its glassy luster and the irregular fracture—absence of definite planes or facets of cleavage, causing the grains to be abraded or rounded nearly alike in all directions. The feldspars, on the contrary, always show a tendency to cleave into fragments having definite, obviously oblique angles, which are perceptible even when the grains are somewhat worn; because of the difference in the ease with which wear takes place in the several directions. Potash feldspar, moreover, which is the most important to be recognized because it indicates a relatively large supply of potash in the natural soil, is but rarely glassy in luster, but mostly dull white, or reddish-white.—The lime and lime-soda feldspars rarely show as definite forms, because of their tendency to form complex crystalline aggregates (twins): and their definite recognition requires somewhat complex (polarizing) appliances in connection with the microscope. In such cases, however, the accompanying minerals (hornblende, pyroxene, mica and others) often afford valuable indications, because of their known association with soda-lime feldspars in certain rocks.

An abundant occurrence of hornblende fragments, characterized by their flat, tabular form, and bottle-green or black tint, indicate, almost always a fairly good supply of lime in the soil, but leaves the potash-supply in doubt. Pyroxene (distinguished by its smooth, polished surface from the angularly-weathering, usually rusty hornblende fragments) rarely occurs with potash feldspar; and soils strongly charged with it are mostly poor in potash.

Mica occurs in so many rocks and is of so little consequence as a soil-ingredient from the chemical point of view, because of its difficult decomposition, that its presence can mostly only serve to corroborate or contradict conclusions as to the derivation of a soil from some particular rock or region. But mica serves a good purpose in improving the tilling qualities of soils. Its thin scales must not be mistaken for the tabular fragments of hornblende.

Calcite in its several forms is mostly easily recognized both by its form under the microscope, and by the effervescence its granules show when touched with an acid. This effervescence can generally be observed on touching the wetted soil with chlorhydric acid, so soon as the content exceeds two per cent; but something depends upon the size of the grains, as when these are very small, the giving-off of gas is less readily noted. To facilitate it, the wetted soil may be warmed before touching it with the acid. The recognition of the presence of lime carbonate in soils is so important as to justify considerable trouble in rendering it definite. When the aid of a chemist cannot be commanded, fairly definite conclusions may be drawn from the character of the native vegetation; regarding which, detailed information may be found in Parts III and IV of this volume. But where, as in the arid region, this criterion is not available, since the controlling factor there is the moisture supply, a presumption may be gained by the application of a slip of moistened red litmus paper to the wetted soil. Should the red paper be turned blue within one or two minutes it would indicate the presence of carbonate of soda (“black alkali”) as well as of lime carbonates: but if blued only after twenty minutes or more, it would indicate the presence of the carbonates of lime and magnesia. If not changed at all, the conclusion would be that either lime carbonate is in very small supply, or that the soil is in an acid condition. (See chapter 8, p. 122).

Saline and Alkali Soils.—The presence of an unusual or injurious amount of soluble salts, as in the case of sea-coast and alkali soils, is commonly easily ascertained in the field; where, if the surface soil is at all seriously contaminated with soluble salts of any kind, these may be seen on the surface during a dry season, forming a whitish efflorescence, which in most cases is definitely crystalline. In doubtful cases a tablespoonful of the surface soil may be leached with water, and the first ten or fifteen drops caught in a clean, bright silver spoon and evaporated. Or the soil may be stirred up with about twice its bulk of water and the mixture be allowed to clear by settling, then evaporating. A slight whitish film will almost always remain in the spoon; but if the amount be somewhat considerable, the presence of soluble salts is very readily recognized by pouring a few drops of clear water on one side of the spot, and then allowing it to flow gently over the spot to another place, where it is again slowly evaporated. Any considerable amount of salts present will be shown both in the diminution of the original spot, and in the soluble residue accumulated where the water was last evaporated. Should common salt be present to any considerable extent, the residue in the silver spoon will, if the last drops be allowed to evaporate slowly, show square or cubical crystals to the naked eye, and certainly to a common pocket lens. The residue may also be tested with red litmus paper for carbonate of soda, which would quickly turn it blue.

More detailed examination requires chemical reagents and experience, but the above tests should be sufficient to prevent the mistaking of mere white spots, whose humus has been destroyed by fermentation caused by bad drainage, with true alkali caused by excess of soluble salts; a mistake not uncommon in both the arid and humid regions.

APPENDIX C.

SHORT APPROXIMATE METHODS OF SOIL EXAMINATION USED AT THE CALIFORNIA EXPERIMENT STATION.

BY R. H. LOUGHRIDGE.

The California Experiment Station has for many years given the farmers of the State the privilege of having their soils examined to ascertain any physical defects, deficiency in plant-food, or the presence of alkali salts. They have quite generally taken advantage of this, and the number of samples of soil sent in each year has been very large.

A complete analysis of a soil-sample requires fully 15 days; hence the necessity of adopting some quick methods for the determination of the main elements of fertility, viz., humus, lime, potash, and phosphoric acid, that would at the same time give results sufficiently accurate for practical purposes. Similarly for alkali salts in the soil; the leaching-out and analysis of which often occupies more than a week.

The following methods have been adopted, which shorten the time of examination for the plant-food of a soil to about one hour, except for potash, which requires a much longer time. For alkali salts the time is reduced to two days, and less if a pressure filter be used.

Humus.—The Grandeau method of ammonia extraction requires the removal of the lime and magnesia with weak hydrochloric acid, washing out of the acid and then digestion with weak ammonia; all of which, with a soil rich in humus, may require many days, though a number of samples may be put through at the same time.

The method adopted to determine adequacy or inadequacy of the humus (for this is all that is intended in this examination) is completed in less than half an hour. It is based on the color of the humus-extract and avoids the necessity of removal of the lime from the soil.

The soil is pulverized in a mortar with a rubber pestle, and passed through a half-millimeter sieve. Seven grams of the fine earth is placed in a test tube with 15 or 20 cc. of a ten per cent solution of caustic potash and boiled for ten or fifteen seconds, then allowed to settle. The humus is dissolved and the density of the color of the solution is an indication of adequacy or inadequacy. A dense black, non-translucent solution shows the presence of at least one per cent of humus in the soil; a deep brown translucent color indicates about one-half of one per cent; while a light brown color clearly shows a deficiency in the soil, and a need of a good green-manure crop.

Lime.—Two grams of fine earth is treated with a little hydrochloric acid, boiled for a few seconds, and ammonia is added to precipitate the iron and alumina; the whole, with the soil-residue, is quickly thrown on a filter to separate the mass from the lime solution, and washed. After adding ammonium chlorid the lime is precipitated with oxalate of ammonia, and its adequacy for soil-fertility judged of by the turbidity of the solution, or the bulk of the precipitate. Or the latter may be filtered off, dried and weighed. We thus obtain a measure of the carbonate and humate of lime present, by comparing it with the precipitate obtained from a soil whose percentage of lime has been correctly ascertained.

Potash.—The determination of potash in the soils requires more time than either of the other ingredients, and is more rarely made by us. Our knowledge of the soils of the State of California obtained through many analyses, gives us a clue to those localities where potash would probably be deficient, as well as to those whose soils are generally extremely rich in potash; the percentages reaching usually from .5 to as much as 1.5 per cent and more.

For the determination, two grams of the fine earth is digested in hydrochloric acid over a steam bath for two days, the insoluble residue filtered off, the filtrate evaporated to dryness to render the silica insoluble, again filtered and the iron; alumina and lime removed by precipitation with ammonia and oxalate of ammonia and filtration. The filtrate is then evaporated to dryness, the ammonia salts destroyed with aqua regia or driven off by heat, and the alkalies changed to chlorids. Any residue is then filtered off and platin-chlorid added to precipitate the potash, which is separated and determined in the usual way, either by reduction of the platinum by ignition, or by measurement in a Plattner’s potash tube.

Phosphoric Acid.—The determination of phosphoric acid is based on the volume of the phospho-molybdate precipitate in a tube made like a Plattner’s potash tube, but having a wider interior diameter for the smaller portion (not greater than 3 millimeters), and a length of 50 mm. With this diameter, one mm. in height of the precipitate obtained by our short method indicates one one-hundredth of one per cent of phosphoric acid in the soil. The unit of measure must be obtained for each tube, unless of uniform diameter, and is ascertained by taking a soil whose phosphoric-acid percentage has been determined gravimetrically and giving it the following quick treatment; which must, of course, be closely followed in each soil to be examined.

Two grams of the fine earth is ignited in a platinum dish to destroy the organic matter, transferred to a test-tube containing 5 cc. of nitric acid and made to boil for only a couple of seconds, thus preventing the solution of silicates to any material extent. It is not allowed to stand, but a little water is immediately added and it is quickly thrown on a small filter and washed with a little water. The phosphoric acid is then precipitated with molybdic acid at the proper temperature; allowing it to settle, the liquid is drawn off and the precipitate transferred to the measuring-tube. It settles into the small part in a short time if the latter is not too narrow, and is then measured with a millimeter scale. This represents the percentage as found in the soil by the gravimetric method, and serves as a guide for other examinations, whose agreement with gravimetric determinations is generally quite close, and quite sufficient for practical purposes. The rapidity with which the solution is made and separated from the soil is a matter of special importance for comparative results, or determination of percentages; for if the acid solution be allowed to stand for some time before filtration from the soil, silica passes into solution also, and the volume of the molybdate precipitate is increased by it; thus vitiating the results and adding to the time required for the method. By this short method the practically important phosphoric acid in the soil may be approximately determined within half an hour.

SHORT METHOD FOR ALKALI SALTS.

The old method of obtaining solutions of the salts by leaching the soil on a filter until all of the alkali had been washed out has been replaced by the following short one. 50 or 100 grams of the well-mixed soil is placed in a bottle containing 200 cc. of water, shaken up occasionally during 12 hours and allowed to settle. The solution may then be passed through a common filter (or preferably a pressure filter) and an aliquot part (usually 50 cc.) of the filtrate evaporated to dryness in a platinum basin and ignited at a temperature just below redness to destroy any organic matter that may be present. The basin and contents are weighed and the soluble salts are dissolved in a very little water and separated by filtration through a small filter into a 50 cc. cylinder and the alkali carbonates and chlorids determined by titration, being calculated as sodium compounds.

The material remaining on the filter and in the basin, consisting of insoluble earth, carbonates and calcium sulfate, is gently ignited in the basin and weighed; the difference between this and the first weight gives approximately the total soluble salts, which should substantially correspond to the titrations made.

The sulfates are determined by differences between these and the total alkalies. The solution may contain some sulfate of magnesia, or calcium and magnesium chlorids, and these are determined gravimetrically.

Nitrates, which may have been destroyed in the first ignition, are determined in the original solution by the picric method. Any magnesia rendered insoluble by the ignition may usually be accounted for as chlorid, unless much nitrate is present which is rarely the case in carbonated alkali. If much nitric acid was found, it should be first assigned to magnesia.

INDEX.

A. PAGE Absorption and movements of water in soils, 221 of solids from solutions, 267 of gases by soils, 272, 275 Acacias, tolerance of alkali, 480 Accessory minerals, 50 Acid, strength used in soil analysis, 341 Acidic and basic eruptive and metamorphic rocks, 49 Acidity, neutrality, alkalinity of soils, 322 Acids of different strengths, analysis with; table, 326, 341 Action of plants in soil formation, mechanical and chemical, 19 Aeration and reduction as influencing nitrification, 147 effects of insufficient, in soils, 280 excessive, injury in arid regions, 280 Aerobic and anerobic bacteria, 144 Air, functions in soils, 279 “ of soils, composition of, 280 Air-space in soils; figure, 108 Alabama, vegetation and soil-characters, 511 Alaska current, effects on California climate, 296 Alinit, 149 Alkali carbonates and sulfates, inverse ratio, 451, 452 carbonates, effects on clay, 62 effects on culture plants; figure, 426, 427 Alkali-heath, range, tolerance of alkali, figure, 544, 545 Alkali lands, crops for strong, 468 effects of irrigation on, 428 efficacy of shading, 457 exceptionally productive when reclaimed, 483 fertilization not needed in, 483 formation from leachings of slopes, 453 geographical distribution of, 423 high and lasting production when reclaimed, 482 inducements toward reclamation of, 481 in the San Joaquin valley, Cal., figure, 425 possible injury to, from excessive leaching, 462 Alkali lands, summary of conclusions, 453 surface and substrata of, 429 utilization and reclamation of, 455 of world-wide importance, 424 vegetation of, 534 Alkali-resistant crops, 455 Alkali salts, black and white, 441 composition of, 439 composition of; general table, 442, 443 distribution in heavy lands, 436, 437 effects on beet crop, 465 horizontal distribution of, 439 in hill lands, 439 in sandy lands, 433, 435 in Salton Basin, distribution of, 4, 36, 438 leaching-down of, 459 nature of, 423 plant food in, 441, 444 reactions between, 449, 450 reduction by cropping, 463 relative injuriousness of, 464 removal from the soil, 458 removal by deep-furrow irrigation; figure, 460, 461 tolerance of various crop plants; table, 466, 467 total in lands; estimation of, 444 underdrainage the universal remedy for, 460 upward translocation from irrigation, 433 vertical distribution in soils, 429, 431, 432, 434 Alkali soils and seashore lands, 422 calcareous character of, 28 composition of, as a whole, 445, 446, 447 how native plants live in, 430 origin of, 422 repellent aspect, cause of, 424 retention of silica in, 392 Alkali spots, white, 286 Alkali, rise of, 428 turning under of surface, 456 weeds as cattle food, 468 study of, by Loughridge and Davy, 535 Aluminic hydrate, in soils of California and Mississippi; table 101, 390 Alluvial soils, 12 Ammonia-forming bacteria, 149 Ammonia gas, absorption of, by soils; figure, 274, 275 Ammonic carbonate, effects on glass, 18 Ancient civilizations, preference for arid countries, 417 rare in humid countries, 418 Apatite, 63 Arid and humid climates, rock-weathering in, 47 Arid and humid regions, criteria of soils of, 371 contrast between soils of, 28 soils of, 111, 371 Arid and humid soils, general comparison; table, 375, 377 Arid belts, subtropic, 298, 299 utilization of, 299 Arid conditions, local, in tropical countries, 401 Aridity, influence upon civilization, 417 Arid region, bunch grasses on soils of, 111 standing hay in, 300 upland soils of; table, 373, 374 Arid soils, productiveness induces permanent civil organization, 412 Arroyo Grande and Yazoo buckshot soils, 345 Asparagus, resistant to salts, 475 Atmosphere, composition of; table, 16 Azotobacter, 156 Lipman on, 156

B. Bacteria, active in soil-formation, 20 aerobic and anaerobic, 144 denitrifying, 148 food and functions of, 145 in soils, numbers of, 142 micro-organisms of soils, 142 multiplication of, 144 nitrifying, 146 Bacterial life, effect on soil, condition, 149 relation of carbonic dioxid to, 281 Bacteroids, 151 Mork figures, 152, 153 Basaltic rocks, 49 Basalts, red soils from, 52 Basic slag, 64 Basin irrigation, advantages of, 243 Bauxite in soils, 101, 390 Beet, sugar, effects of salts on, 474 tolerant of common salt, 474 Bhil soils, 414 Bicarbonate of soda, 78 Black-alkali lands, difficulty in draining, 462 neutralizing of, 457 waters, use of, 250 why so called, 78 Black earth of Russia, humus in; table, 130 Black sand, 45 Black prairie soils, 53 Black soils and lands, 283 Blizzards in continental America, 298 Blown-out lands, 9 Blue tint in clays and subsoils, 45 Bodengare, 149, 150, 281 Bog ore, formation of, in subsoils, 46, 66 Bones, composition of, 64 Bone meal, efficacy of, 65 Borax, borate of soda, 79 Bottom water, 227 rise of, from irrigation, 227, 230 Bottoms, first and second, contrast between, 506, 507, 509 Bottoms, first, tree growth of, 507, 509 Brahmaputra alluvium, Assam, 413 Brown iron ore, 44 “Buckshot” soils of Yazoo bottom, 116 “Bunch grasses” as alkali-resistants, 471 Burning-out of humus, effects of, 118 Burrowing animals, work in soil-formation, 160

C. Calcareous clay, crumbling on drying, 116 formations, predominance in Europe, 525 soils, definition of, 367, 496, 524 solubility of alumina and silica in, 389 subsoils, and hardpans, 162 Calciphile, calcifuge and silicophile plants, 521 Calcite, calcareous spar, 39 recognition of, 39 Caliche, in Chile, Nevada, and California, 66, 67 Capillarity, 189 Capillary water, reserve of, 229 rise of, 202 to 207 Carbonated water, action on feldspar, 32 action on silicates, 18 universal solvent, 17 Carbonate of soda, 77 injury to soils and plants, 78 Carbonates, chlorids and sulfates of earths and alkalies, reactions between, 449, 450 Carbonic acid, 17 secreted by roots, 20 Carbonic dioxid, absorption of, by soils, 274 heavily absorbed by ferric and aluminic hydrates, 278 occurrence, formation, 17 relation to fungous activity, 281 Cascade range, climatic divide in N. W. America, 297 Caves in limestone regions, 41 Celery, moderate tolerance of alkali, 475 Centrifugal elutriator, Yoder’s, 92 Cereals, alkali-resistance, barley, gluten wheats, 471 Channels, cutting-out by gravel, 6 Charcoal, absorption of gases by, 276, 277 Chemical absorption by soils, 270 action of roots, 20 analysis of soils (in general), 323 character of soil, recognition of, 322 decomposition, causes intensifying, 21 processes of soil formation, 16 Chile saltpeter, 66 Chernozem, 130 analyses of, table, 364 Chestnut, American, a calcifuge tree, 491, 519 Chlorin, largest ingredient of sea water, 27 Chlorite, 36 Chlorosis of vines in marly lands, 526 Churn elutriator, Hilgard’s; figure, 91 Circling of hill lands, 220 Citrus fruits, injury to, from alkali, 478 lemons most sensitive, 478 sensitiveness to common salt, 477 Classification of rocks, 47 of soils, 10 Clay as a soil ingredient, 83 colloidal, 59 functions of, in soils, 59 maintains crumb structure, 110 Clays, claystones, clay shales, 48 colors of, 58 formation, flocculation and deposition of, 33 maturing of, 60 plasticity and adhesiveness, influence of fine powders on, 85 influence of ferric hydrate on, 85 Clay-sandstones, soils from, 57 Clays, separation of, by subsidence, by centrifuge, 89 varieties, enumeration of, and characters, 57, 58 fusibility of, 58 Claystones, soils from, 59 Cleavage of rocks, 3 Cleopatra’s needle, 2 Climate, 287 Climatic and seasonal conditions, 21 Climates, continental, coast and insular, 297 Coffee soils, calcareous, 417 Colloidal clay, amount in soils. Table, 84 analysis of, by Loughridge, 385 effects of alkali carbonates upon, 62 investigation by Schloesing, 59 properties of, 61 separation of, by boiling and kneading, 61 Colloid humates, 133 Colluvial soils, 12 Colors of soils, advantages of, 283 Common salt, injuriousness in soils, 76 recognition of, 76 removal from soils, 76 Conglomerates, 48 Conifers, tall growth of, in arid regions, 517 Contraction of soils in wetting and drying, 114 Co-operation, favored by need of irrigation, 419 Corsican and maritime pine, ash analyses, 520 Cotton, compact growth and heavy boiling on calcareous soils, 503 Cracking of clay soils in drying, 113 Cressa; range, tolerance of alkali, figure, 545, 546 Creep, 12 Crops, alkali-resistant, 455 Crumbling of calcareous clays on drying, 116 Crumb-structure of soils; figure, 110 Crusting of soils, effects of, 111, 117, 221 Cultivated soils, analysis of, 325 investigation of, 316 Cultural experience the final test, 324 Cutting-out of channels by water-borne gravel, 6 Cypress, different forms of; figures, 507, 508

D. Date palm, resistance to alkali, 478 Decomposition, chemical, of rocks, 16 Decolorizing action, of soils, charcoal, 267 Deep-rooting of native plants in arid region, 174 Deforestation, effects of, 219 Deltas, formation of, 7 Denitrifying bacteria, 148 Deserts, effects of winds in, 8 Desert sands, only lack water to become productive, 420 Dew, formation of, 307 rarely adds moisture to soils, 308 within the soil, 308 Differentiation of soil and subsoil, causes of, 121 Distance between furrows and ditches, 241 Dolomite, 42 Drainage, rights-of-way for, 461 Drainage waters, use for irrigation, 250 Drain waters, analyses of, table, 22 leaching effects of, 271 Drouth, resistance to, in arid soils, 167 Dust soils, nature of, 104 slow penetration of water in, 105 Dust storms, 9 Dynamite, used for shattering dense substrata, 181

E. Earth’s crust, known thickness, xxiv Earthworms, action of in soil-formation, 158 Ecological studies, 314 Egypt, obelisks of, 2 Elements constituting earth’s crust, table of, xxiv important to agriculture, list of, xxiv Elutriator, Hilgard’s, figure, 91 Epsomite, epsom salt, in soil, 78 Eremacausis, 129 Erosion in arid regions, 219 in Mississippi table lands; figures, 218 lowering of land by, 15 of rocks by sand; figure, 10 Eruptive rocks, basic and acidic, 49 rocks, soils from, 52 Eucalyptus, tolerance of alkali, 480 European observations on plant distribution, 519 standards of plant-food adequacy—Maercker’s table, 369 Europe, predominance of calcareous formations in, 525 Evaporation and crop yields, calculated, 193 and crop yields, observed (Fortier), 194 and plant growth, 193 counteracting, in alkali lands, 455 dependence on air temperature; Fortier’s experiments, table, 255 from reservoirs and ditches, 257 from water surfaces, 254 wet and moist soils, 254 in different climates, 192, 256 in different localities, California, 255 restrained by loose surface layer, 255 through roots and leaves, amount of, 262, 263 Expansion by oxidation, 18

F. Farmyard or stable manure, 72 Feldspars, weathering of, 31 products of, 32 Ferghana, alkali lands in, 441 Ferric hydrate, effects of, 100 functions of, in soils, 285 high absorptive power of, 277 in Hawaiian soils; table, 356 more diffused in humid than in arid soils, 392 Ferric phosphate, unavailability of, 356 Ferroso-ferric hydrate and oxid, 18, 45 Ferrous oxid, 18 Ferruginous lands, injury from swamping of, 233 Fertilizers, mineral, 63 waste of, by leaching, 269 Flocculation and floccules, 91 Flocculated structure; cements maintaining, 110, 111 Flood-plains of rivers, 14, 15 Fool’s gold, 75 Force exerted by roots, 19 Forecasts, general, of soil quality in forest lands, 507 of soil values, popular, 313 Forest trees, forms of, 499 to 502 of Atlantic states on alkali lands, 481 Form and development of trees, differences in, 498 Forms of leaves, variation in, 502 black-jack oak, 499, 501 post oak, 499, 500 trees, deciduous, in arid region, 516 willow, scarlet, black and Spanish oaks, 502 Freezing water, effects of, 3 Frost, effect of soils, 118 Fruiting, favored by lime in soils, 503 Fungi and molds, action of, 123 functions in humus-formation, 157

G. Gases, absorption of, by soils, 272, 275 partial pressure of, 276 Germination of seeds, 309 Glacier flour, fineness and fertility of, 5 physical analysis of, 5 Glaciers, grinding and abrasion by; figure, 3 Glauber’s salt, 77 Glauconite, in calcareous sandstones, 56 Gneiss soils, 51 Gobi desert, migration of lakes, 9 Going-back of orchards, 182 Grain-sizes, effect on percolation; table, 224 influence on soil texture, 100 Grandeau method of humus estimation, 132 Granite soils, potash and phosphoric acid in, 50 Granitic rocks, weathering of, 47 sand, formation in arid climates, 2 Grano-diorite soils, of Sierra Nevada, 51 Granular sediments, influence upon tilling qualities, 102 Grape-vine, alkali, tolerance of, 475 Grasses, cultivated, sensitive to alkali, 471 Greasewood, range, tolerance of alkali; figure, 542, 543 Greenstones, soils from, 51 Ground water, depth most favorable to crops, 228 variation of surface of, 228 Gulf-stream, 295 Gypsum or selenite, formation from sea-water evaporation, 42 how recognized, 42

H. Halite, 76 Hardpans, causes, formation and cements of, 185 Hardpan, physical, analysis of, 103 plowsole, 241 Hawaiian Islands, humid and arid sides of, 297 soils, analyses of, 356 Hay bacillus; figure, 149, 150 Heat and cold, effects on rocks, 1 of high and low intensity, 304 reflection and dispersion from soil surface, 304 relations to soils and plant growth, 301 trapping of suns, 288 Heaviest clay soils, physical analysis of, 115 Heaving-out of grain, 119 Hematite, 44 Herbaceous plants as soil indicators, 517 Hog-wallows, 114 Hornblende and pyroxene, 33 weathering of, 33 Horsetail rushes, secretion of silica by, 31 Humates and ulmates, 133 cementing effects of, 111 Humid and arid climates, rock-weathering in, 47 Humid region, upland soils of; table, 372, 374 Humification in soils, 20 normal conditions of, 129 tests; Snyder, tables, 140 Humin substances, formation of, 123 Humus, amidic constitution of, 125 and coal, amounts of, from vegetable substance, 128 amount in soils, 133 ash of, from Minnesota soils, analysis, 134 decrease of nitrogen-content with depth, 135 determination in soils, 132 distribution in the surface soil, 157 functions in soils, 21 in arid and humid regions, 138 in black earth of Russia, 130 in Minnesota soils, 131 in North Dakota soils, 133 in the surface soil, 120 losses from cultivation and fallow, 131 nitrogen of, 124, 135 percentage in soils, and nitrogen-content of, tables, 135, 136, 137 porosity of, 124 progressive changes in soils, 126 relation to bacterial content, 144 scanty in arid soils, but rich in nitrogen, 397 substances, physical and chemical nature of, 124 variation of, with original materials, 139 volume weight of, table, 125 versus adipocere, 140 Hydraulic elutriation, 90 Hydromica, 35 Hydrous silicates in soils of arid region, 388

I. Ice-flowers on soils, 119 Immediate plant-food requirements, ascertainment of, 333 productiveness, chemical tests of, 337 productiveness vs. permanent value of soils, 318, 327 India, climatic contrasts, 401 Indian soils, table of analyses, 410 412 types of soils, 411 Indo-Gangetic plain; calcareous hardpan, kankar, 411 Injury from excessive runoff, prevention of, 220 to plants from the various salts, 531 to soils and plants from carbonate of soda, 78 Insects, work in soil-formation, 160 Insoluble residue of soils; less in arid than humid, 384 Insufficient rainfall, leaves sea salts in soils, 28 Insular climate, of Britain, western Europe, 298 Introduction, xxiii Injury from swamping, permanent, 232 Iron carbonate solution, how formed, 44 coloring clays, 58 minerals, 44 pyrite, how recognized, 75 Irrigation, basin, advantages and disadvantages, 244 by check flooding, 237 flooding, 237 furrows, 238 lateral seepage, 242, 241 shallow, deep and wide furrows; diagram, 239 surface sprinkling, 237 underground pipes, 245 ditches, leaky, effects on alkali lands, 429 excessive surface rooting caused by, 245 methods of, 236 necessitates co-operation, 419 Irrigation water, abundant use of saline, 249 duty of, 251 economy in use of, 243 effects of saline, figures, 247 heavy losses in using, 252 limits of salinity, 246, 248 loss by evaporation, 252 loss by percolation; diagram, 253 quality of, 246 saline, how to use, 249 testing penetration of, 242 temperature of, 244 Irrigation, winter, advantages of, 236 Isinglass, 43

J. Janesville loam, chemical analysis of, 331 Japan current, 296 Jasper and hornstone pebbles, weathering of, 30

K. Kainit, composition of, 71 Kaolinite and clay; kaolin, 32 assumes plasticity on trituration with water, 60 crystalline form of, 22, 59 lacks plasticity, 60 Kaolinization, results in zeolite-formation, 395 slow in arid regions, 87, 386

L. Landholding, units of, smaller in arid than in humid region, 420 Landlocked lakes, water of, 27 Land plaster as a fertilizer; effects on soils, 43 Landslides, 12 Laterite soils, Wohltmann’s definition, 416 Terra roxa of Brazil, 416 Leaching of the land, 22 Legumes, bacteria of, 150 mostly sensitive to alkali, 472 Leguminous plants, mostly calciphile; exceptions, 518 Leucite, potash content, 32 Lichens, action on rock-surfaces, 19, 20 Lignites and coal, how formed, 127 Lime a dominant factor in productiveness, 353 Lime carbonate in sea water, 26, 27 removed from earth’s surface, 41 summary of effects in soils, 379 Lime-content, effects of high, in soils, 365 effects on availability of phosophates, table, 366 “Lime-country is a rich country”, 365 Lime, excess of, in arid soils, 378 Lime feldspars, leave lime carbonate in soils, 32 in alkali lands protects plants from salts, 532 lands, failure of tea on, 414 Lime-loving trees, 490 to 492, 497 Lime, most abundantly leached out, 24 percentages, what are adequate, 367 in coast-belt soils, 496, 497 in heavy clay soils; table, 368 Lime renders lower amounts of plant-food adequate, 354 Limestone countries, 53 Rotten, 54 soils, excluded from comparison of arid and humid soils, 376 residual, 53 Limestones, impure, as soil-formers, 40, 53 residual soils of, how formed, 40 soft, or marls, 40 slow disintegration of pure, 63 Limit of acid action on soils, investigation of, by Loughridge, 340 Limonite, 44 Loamy and sandy soils, show little shrinkage, 117 Loose surface layer, illustration of effect, figure, 258, 260 prevention of evaporation by, 257 Loss of humus in summer mulch, 132 Louisiana, vegetation and soil-characters, 512 Lowland tree-growth, 506 Lysimeter, 227

M. Madagascar, character and soils of, 405, 406 climate and rocks of, 406 methods used by Müntz and Rousseaux, 406 potash and lime leached into valleys, 407 red soils, 407, 409 table of soil analyses, 408 Madras, red soils of, 415 Magnesia, effects of excess over lime, 382 exceeds lime in tropical soils, 405 high in arid soils, 381 leached out next to lime, 24 proper proportions to lime, 383 Magnesian limestones as soil-formers, 42 Magnesian soils largely poor, 36 Magnetite, 45 Maize and sorghums, alkali-resistance, 471 Maize roots in humid and arid region, 175, 176 Manganese, more in humid than arid soils, 383 stimulant effects on crops, 383 Marble and limestones, formation of, 39 Marls, gypseous and calcareous, 43 Marly substrata, 186 Marine saline lands, 527 first crops for, 533 reclamation for culture, 534 Matière noire; active nitrification of, 132, 360 Mechanical analysis of soils, 88 Melilots, white and yellow, alkali resistance, 473 Mesas of arid region, 14 Mesopotamia, rehabilitation of, 421 Metamorphic rocks, 46 Methods of irrigation, 236 soil analysis, 325 Mica as a soil ingredient, 35 weathers slowly, 35 mistaken for gold and silver, 35 Mica-schist soils, 51 Micro-organisms of soils, 142 Mineral fertilizers, 63 ingredients of soils, minor, 63 Minerals injurious to agriculture, 73 major soil-forming, and rock-forming, list of, 29 tints of, 18 unessential or injurious to soils, 75 Mirabilite, 77 Mississippi, changes in vegetation from east to west in northern, 490 investigations in, by writer, 489 northern, vegetative belts in; map, 490 vegetative belts, descriptions of, 490, 491, 492 Mississippi river, sediment carried by, 7 Mississippi, southern, central prairie, long-leaf-pine belts, 493 coast-belt; pine meadows; profile, 495 live-oak or shell hammocks, 495 Mississippi valley, climate of, 298 Mississippi water, annual variations in, 25 generalized composition of, 25 Modiola, of Chile, 469 Moisture hygroscopic, table, 196 influence of temperature and air-saturation, 197 method of determining, 197, 198 Mitscherlich’s objections, 199 utility to plant growth, 199 available to growing plants, 211 distribution in soil, as affected by vegetation, 264 evaporated from forests, 265 Eucalyptus, 265 in Russian forests and steppes, 265 requirements of crops in the arid region, 212 Loughridge’s tables of same, 214 supplied by tap roots, 229 useful to crops retained by alkali lands, 433 wasted by weeds, 264 Moraines, in North Central states, 5 Mosses, follow lichens in rock decomposition, 20 Moulds and fungi, action of, 123 Mountain chains, arid climate under lee of, 294 effects of, on rainfall, 293 Muddy waters, 251 Muir glacier, analysis of mud, 5 Mulches, loss of humus, 132 Mulching with straw, sand, 266 Mustard family, sensitive to alkali, 473 Myrobalan root, use for grafting in alkali lands, 479

N. Native vegetation, basis of land values for farmers, 488 causes governing its distribution not an unsolvable problem, 489 result of struggle for existence, 487 Native grasses for alkali lands, 470 Native growth, cogency of conclusions based on, 314 New Mexico, soils from; analysis, 378 Nile water, Letheby’s analyses of, 25 Nitrate deposits, origin of, 67 of soda, 66 Nitrates, waste of, by leaching, 24, 68 Nitrification, active in matière noire, 360 Nitrification and denitrification, 145 in alkali lands, 68 in soil of “ten-acre tract.”, 359 intensity in arid climates, 68 list of substances favoring, 147 of organic matter in soils, experiments, 358 not active in unhumified matter, 359, 360 Nitrifying Bacteria, 146 Nitrobacterium; conditions of activity, 146 Nitrogen-absorbing bacteria, 156 Nitrogen, absorbed more abundantly than oxygen, 278 accumulation of, in humus, 124 adequacy in humus, lowest limit of, 363 in soils, 357 availability of, in soils; ascertainable, 363 content of humus, 135 deficiency, pot test, figure, 362 determination of, in soils, 357 hungry soils; table, 361 percentages in humus, what are adequate, 360 supply of plants, views on, 150 Nitrosomonas, figure, 246 Nodules of legumes, 151 North Central States, herbaceous vegetation on calcareous soils, 514, 515 lowland growth in uplands, when, 515 vegetation and soil-character, 513 Nutritive salts in alkali, 441

O. Ocean currents, Gulf stream and Japan stream, 295, 296 Olive, resistance to alkali, 478 Organic and organized constituents of soils, 120 Organisms influencing soil-conditions, 142 Oxalic acid, secretion by lichens, 19 Oxidation, expansion by, 18 Oxids constituting earth’s crust; table, 31 Oxygen, action in weathering rocks, 18 proportion of, in earth’s crust, 30

P. Pamperos, 9 Peat bogs, 122 Peaty soil, shrinkage, 117 Percolation in natural soils: diagram, 223, 225, 226 rate of, as influenced by grain-sizes, 224 Permanent value of land vs. Immediate productiveness, 340 Physical and chemical causes of vegetative features, 505 conditions of plant growth, 319 Physical analyses, correlation with popular names, 96 results of, 94 table. Mississippi and California soils, 98 analysis of soils, 88 constituents of soils, 10 Physico-chemical investigation of soils, 313 Physiological soil analysis, 333 Phosphate fertilizers, importance of, 65 Phosphate fertilization, in arid region, 393 in California, 393 Phosphoric acid, limits of adequacy in soils, 355 minute amounts leached from soils, 24 no constant difference between arid and humid soils, 393 rendered inert by ferric hydrate, 355 Phosphorites, low-grade, of Nevada, Russia, 63, 64 Plane tree, oriental, resistant to alkali, 480 Plant-adaptation “varying from province to province”, 523 Plant associations, plant formations, 315 Plant distribution, Thurman’s physical theory of, 519 Plant-development under different temperatures, 309 Plant-food, accumulation in finest parts of soils, 87 high percentages mean high land value, 346 ingredients, condition of, in soils, 319 in virgin soils, lowest limit of, table, 352 limits of adequacy, 353 minute amounts may produce large crops, 410 percentages, what are high, 346 percentages, low, 346 water-soluble, reserve, unavailable, 320 Plant-growth on arid subsoils, 166 Plants, deep-rooting in arid region, 174 indicating irreclaimable alkali lands, 535, 536 Plant root action, cannot be imitated in laboratory, 324 Plasticity, absence of, in fine powders, 60 of clay, causes of, 60 lost by burning, 60 Plot tests, difficulties and uncertainties of, 334 plan of, figure, 335 Plowsole, how formed, by shallow irrigation, 186, 241 Poor chalk lands, 525 Pore-space, 108 Porosity of humus, 124 Port Hudson bluff, lignite in, figure, 128 recession of, 116 Potash, abundant in arid soils, 395 and soda in arid and humid region, 394 Potashes, production of detrimental to agriculture, 69 Potash feldspar, supplies potash to soils, 32 fertilization first in humid, last in arid region, 396 from sea water, 69 limits of adequacy in soils, 354 minerals, orthoclase feldspar, 68 preferential retention of, in soils, 272 Salts, Stassfurt, 69 slightly leached out, 24 sulfate, high-grade, 71 Pot-culture tests, 336 Powders, absorption of various gases by, table, 277 Prairie soils, black, 53 Preparation of soils for physical analysis, 89 Productive capacity and duration, forecast of, 346 Progress of humification and formation of coal, table, 126, 127 Pulverulent soils of arid regions, 87 Purifying action of soils, 269 Putrefactive processes, relation to carbonic gas and anaerobic bacteria, 282 Putty soils, 103 Pyroxene, augite, 33, 34

Q. Qualifications required for soil study, 524 Quality of irrigation water, 246 Quince, resistance to alkali, 479 Quartz and allied rocks, 29 sand most prominent ingredient of soils, 30 veins, formation of, 31

R. Rain belts, temperate and tropical, 295 Rainfall, amount of, 215 distribution in California and Montana, 290 in the United States, 215 most important, 290 on the globe, figure, 294 influence on soil formation, 22 insufficient, forms alkali soils, 28 leaves lime behind, 28 natural disposition of, 216 Rains, beating, 221 cold and warm, 302 Reclaimable and irreclaimable alkali lands, 534 Red foothill soils of California, 34 Red or rust-colored soils, 34 advantages of, 284 Regur soils, Deccan, India, 414 formation of, 415 “guvarayi” hardpan, 415 present production, 414 Reh of India, 440 Reserve plant-food in soils, 320 of zeolites, carbonates, phosphates, 321 Residual soils, 11, 13, 22 Rhizobia, adaptation to symbiosis, 154 inoculation of soils with, 154 increase of crops by inoculation with, 155 of legumes, 150 mode of infection, 154 varieties of forms, 154 Rhubarb, sensitive to alkali, 475 Rhyolites, soils from, 53 River bars, formation of, 7 Rivers, amount of dissolved matters carried by, 24 flood-plains of, 13, 14 sediment carried by, 24 waters, analyses of, table, discussion, 23, 24 white and green, 4 Rock crystal, 29 Rocks as soil-formers, 47 chemical decomposition of, 16 cleavage of, 3 definition of, xxiii disintegration of, under extremes of temperature, 2 effects of heat and cold on, 1 erosion of by sand, 10 forming minerals, 29 fragments, rounding of, by flowing water, 6 Rock powder, 85 Rock-weathering in arid and humid climates, 47 Rohhumus, 122 Rolling of soils, of influence of, on heat, 305 Root action, limitation of, 351 Root bacillus, figure, 149, 150 Root crops, effects of alkali upon, 474 Root development in the arid and humid regions, 169 to 176 Rooting, deep, from proper irrigation, 243, 245 Roots, chemical action of, 21 force exerted by, 19 secrete carbonic acid, 20 Root system in the humid region; figure, 168 Rotten Limestone, soils from, analyses, 54 Runoff of rain water, 216 Russia, black earth of; roots and humus in, 130, 363 Rye grass, giant, of Northwest; uses, 470

S. Saline and alkali lands, vegetation of, 527 plants, analyses of ashes of, 530 selective power of, 531 Saline and xerophile vegetation, similarity of, 528 Saline contents of waters, variations of, 250 solutions, structural and functional differences caused by, 528 vegetation, general character of, 527 Saltbushes, Australian, growth and use in California, 469 of Great Basin, probable usefulness, 468 Saltgrass; range, tolerance of alkali, figure, 546, 547 Salton Basin, profile of salts in, 438 Salts, absorption of, by saline plants, 529 Saltwort: range, tolerance of alkali, figure, 540, 542 Samoa and Kamerun soils, analyses by Wohltmann; method, 402 table of, 404 Samphire, Bushy and Dwarf; range, alkali-tolerance, figure, 538, 539, 540 Sand blasts, effects on cobbles, 10 coarse, effect of, on clays, 105 erosion of rocks by; figure, 10 hammocks, of Gulf coast, 56 Sands of arid and humid regions, differences in, 86, 386 table of analyses, 387 Sand, silt and dust, 85 Sandstones, 48 argillaceous, 57 calcareous, formation of, 56 rich soils from, 56 dolomitic, often form poor soils, 56 ferruginous, poor soils from, 56 siliceous, poor soils from, 55 varieties of, 55 zeolitic, soils from, 57 Sandstone soils, lightness of, 55 soils, poor, of humid region, 55 Sand storms, 9 Sandy lands, of arid regions, highly productive, 386 Sandy soils, 30 Schöne’s elutriator, figure, 90 Shrinkage, extent of, in drying soils; figure, 113, 114 Schübler on calcareous soils, 115 Sea water, average composition of, table, 26 chief ingredients useless to plants, 28 minor constituents of, 27 sources of salts in, 26 Sedentary soils, 11, 13, 40 Sedimentary rocks, 47, 48 Sediment deposited by Mississippi in Gulf, 7 Sediments, exhibition of, from physical analysis, 95, 96 number of, in physical analysis, 93 table of diameters and hydraulic values, 94 Seeds, germination of, 309 Semi-humid and semi-arid region, 377, 397 Serpentine, 36 Sieves, use in physical analysis of soils, 88 Silica, absorption and secretion by plants, 31 and alumina, soluble; quantitative relations, 385 solubility in water, 31 soluble, retained in alkali soils, 391 Silicate minerals, 31 Silicates of soda and potash, soluble, 31 Silicon, abundance of, in rocks, xxxi Silicophile plants, a fiction, 522 Sinkholes, 43 Soapstone, 36 Soda in arid and humid regions, 394 Soda, nitrate of, 66 Sodium salts, leached out by drains and rivers, 24 Soil analysis, change of views regarding, 317 discrepant methods used in, 402 practical utility of, 318 Soil and subsoil, causes and processes of differentiation, 120 ill-defined, 120 Soil bacteria, numbers of, 141 Soil character, recognition from native vegetation, 487, 511 Soil-dilution experiments, 347 figures, 348, 349, 350 table of, 350 Soil-examination, short approximate methods for, used at California station, 560 summary directions for, in field or farm, 556 Soil-formation influenced by rainfall, 22 physical processes of, 1 Soil-forming processes accelerated by high temperatures, 398 Soil-grains, number of, 99 surface of, 99 determination by air-flow, 99 by “Benetzungswärme”, 99 investigation, historical review of, 313 moisture, regulation and conservation of, 234 phosphates, solubility in water; Schloesing fils, 332 probe, mode of using, 177 profiles in arid and humid region, 165 Soil, samples, directions for taking, by Calif. Station, 553 sedentary or residual, 11, 13, 40 study, qualifications needed for, 524 surveys, early, of Kentucky, Arkansas and Mississippi, 316 temperature, annual range near surface in arctic and tropical regions, 303 change with depth; table, 303 influence of evaporation on, 307 influence of soil material, 306 influence of surface conditions, 303 influence of vegetation and mulch, 305 tests by crop analysis, Godlewski, Vanderyst, 337, 338 by extraction with organic acids; Dyer, Maxwell, 339 water, different conditions of, 195 Soils, acid-soluble and water-soluble portions most important, 324 alluvial, 12, 13 ancient, in geological formations, xxix calcareous, definition of, 367, 496, 524 classification of, figure, 11 colluvial, 12, 24 definition of, xxix derived from various rocks, 49 effects of crusting on, 221 indefinite action of dilute acids on, 326 interpretation of analyses; Wohltmann, 403 physico-chemical investigation of, 313 (see Table of Contents) Solar radiation, influence of, 302 Solubility, continuous, of soils in water, 328 King’s table, rich and poor soils, 330 Schultze’s table, rich soil, 328 Ulbricht’s table, poor soil, 329 Solvent action of water upon soils, 327 power of water, 17 Solubility, increased with nitrogen-content, 141 Sour grasses, 123 humus, antiseptic properties of, 122 soils, 122 Souring of soils, by cultivation, 123 Stable or farmyard manure, 72 composition of, table, 73 green-manuring only substitute, 74 method of using, in humid region, 74 physical effects of, 73 use of, in the arid region, 74 Stalactites and stalagmites, 41 Stassfurt Salts, discovery of, 69 importance to agriculture, 70 origin of, 70 Stassfurt Salts, nature of, 71 Stonecrops, succeed mosses, 20 Stone fruits, resistance to alkali, 478 Stratified rocks, derived from crystalline, 29 Stunted growth, caused by shallow or very heavy soils, 504 Sturdy growth on calcareous lands, 502, 503 Subsidence method, 89 Subsoils, arid region, 163 and deep plowing, 164 calcareous, 162 rawness of, in humid climates, 163 Substrata in arid region, importance of, 173 faulty, with figures, 177 to 180 impervious, injury from; figure, 181 leachy, 182 marly, 186 Subterranean rivers, 41 Sulfate of potash, high-grade, 71 of soda, dust from, 77 injuriousness to plants, 77 occurrence in arid regions, 77 Sulfates, reduction of, 232 Sulfuric acid in arid and humid regions, 394 Summer mulch, loss of humus in, 132 Sunflower family, resistance to alkali, 473 Sun’s heat, penetration into the soil, 302 Surface crusts, formation of, 111, 117 physical analyses of, 118 Surface, hydrostatic and ground waters, 215 Surface waters, chemical effects of percolation, 161 physical effects of percolation, 161 Swamping of alkali lands, consequences of, 451, 463 irrigated lands, results of, 231 Symbiosis, adaptation to, of Rhizobia, 154 Szek of Hungarian plain, 440

T. Tabashir, 31 Talc and serpentine, 36 Tap-roots, moisture supplied by, 229 Tea, failure on calcareous lands, 414

Temperature, annual mean of, 289 conditions, ascertainment and presentation of, 288 extremes, on high mountains and plateaus, 288 of stellar space, 288 seasonal, monthly and daily means, 289, 291 Temporary vs. permanent productive capacity of soils, 340 Tennessee and Kentucky, vegetation and soil-character, 513 Terraces, river and lake, 14 Testing penetration of irrigation water, 242 Textile plants, tolerance of alkali, 475 Thomas or basic slag, 64 Thurman’s physical theory of plant distribution, 519 Tillage; effects of; figure, 109, 110 how maintained in nature, 111 Titanium in soils, xxxi Time of acid-digestion, different; table, 342 Tolerance of alkali by culture plants, 463 alkali plants; table, 548, 549 Topography, influence of, on climate, 293 Trachytes, 53 Trona, Urao, 77 Tropical soils, 398 are highly leached, 400 often highly colored with iron, 400 do not need early fertilization, 399 humus in; abundant, but low in nitrogen, 399 few determinations made, 399 possible calculation of, 399 investigations of, 401 laterites, not always rich in iron, 400 mostly have low plant-food percentages, 400 resemble the “nimble penny”, 400 Tubercles of legumes, figures, 151, 154 Tufa, calcareous, 41 Tussock grass, food value of, 470 range, alkali-tolerance, figure, 536, 537

U. Ulmin substances, 122 Underdrainage, advantages of, 235 Underdrains, effects of, 234 Unhumified organic matter does not nitrify, 148 Unhumified vegetable matter, utility of, 135, 360 United States, good field for comparative soil study, 524 Upland and lowland growth in arid and humid regions, 515 Usar lands of India, character of, 440 not all alkali lands, 440

V. Vegetative belts, lime a governing factor of, 492 Virgin lands, advantages of soil study in, 318 Virgin soils, analysis by extraction with strong acids, 340 Vivianite, 65 Volatile part of plants, xxxii Volcanic ash, form soils rapidly; soils from, 20, 52 Volcanic glass, 53 Volume of soils, changes on wetting and drying, 122 Volume-weight of soils, 107

W. Walnut, black, a lime-loving tree, 490 to 497 tolerant of white alkali, 479 Washing-away and gullying of land, 217 Water, capillary, 201 ascent in soil columns, figure, 202, 205 uniform sediments, figure, 204, 207 held at different heights in soil column, table, 208 expansion and contraction in absorbing, 208, 209 maximum and minimum of water-holding power, termination of; figure, 202, 207 movements in moist soils, 210 carbonated, solvent power, 17 carrying power, 14 controlling factor of soil temperature, 301 density of, 190 effects of flowing, 5 Water extraction of soils, practical conclusions from, 332 Water, hard, 41 hygroscopic, 196 of lan-locked lakes, 27 loss of, by irrigation in shallow furrows, 240 physical factors of, 188 regulation of temperature by, 191 relations to heat, 189 requirements of growing plants, 192 plants in arid regions, 195 sidewise penetration of, in soils, 241 of soils, chapters on, 188, 215, 234 solvent action upon soils, 327 solvent power, 17, 191 Water-soluble plant-food, 321 specific heat of, 190, 191 table, 227 vaporization of, 191 Watery soil extracts, from European soils; tables, 327, 329 American soils, King, 329, 330 Wave action on shores, figure, 7 Weathering, by oxygen, carbonic acid, water, 16, 17 “ in humid and arid regions, 2, 86 Weight of soils, per acre-foot, 107 White soils, nature of, in humid regions, 285 in arid regions, 286 Wind deposits, 105 Winds, action of, in forming soils, 8 cyclones, and anti-cyclones, 293 effects of, in deserts, 8 heat the cause of, 291 land and sea breeze, 291 trade, and monsoons, 291, 292 Winter irrigation, 236 Wire-basket tests, of Bureau of Soils, 337

X. Xerophile vegetation, similarity to saline, 529

Y. Yazoo bottom, soils of, 116 Yazoo “buckshot” and Arroyo Grande soils, 345

Z. Zeolites, decomposition by acids, 36, 38, 39 exchange of bases in analcite and leucite, 37 formation of, 37 importance in soils, 38 rocks cemented by, 38 Zeolitic sandstones, 57

AUTHORS REFERRED TO.

[NOTE.—In cases where no special credit is given in this volume for investigations made or data given from the Southwestern States and the Pacific Coast, these should be understood as work done, mostly under the writers direction, or by himself and assistants, in connections with the geological surveys of Mississippi and Louisiana, as well as the Tenth Census of the United States, by Drs. Eugene A. Smith and R. H. Loughridge; the chemical work for the Pacific Northwest, under the auspices of the Northern Transcontinental Survey, by M. E. Jaffa and Geo. E. Colby; that in California, at the Experiment Station, by the latter two, Dr. R. H. Loughridge, and temporary assistants. It would be impossible to segregate, without excessive prolixity, the credit to be assigned to each of these participants.]

A. Adametz, L., 142, 281. Agassiz, L., 4. Aso, K., 383.

B. Bamber, —, 401, 410, 414. Batholomew, J. G. 294. Beyerinck, M. W., 151, 156. Blumtritt, E., 276. Bonnier, G., 521. Böttcher, O., 393. Boussingault, J. B., 151, 276, 313. Brick, —, 528. Brock, see Morck, D. Burri, R., 148. Butler, O., 151.

C. Cameron, F. K., 380, 466, 532, 533. Clarke, F. W., XXIV, 23. Colby, G. E., note above. Colmore, C. A., 448. Contejean, Ch., 521, 523, 531. Coville, F. V., 536. Crochetelle, J., 146, 147.

D. Darton, N. H., 10. Darwin, Ch., 158. Davy, J. B., 535. Deherain, P. P., 146, 147. Detmer, W., 127. Djemil, —, 159. Duclaux, P. E., 144. Duggar, J. F., 155. Dumont, J., 146, 147. Dyer, B., 339, 357.

E. Ebermayer, E., 279, 305. Eckart, C. F., 212. Eichorn, —, 327. Ermann, G. A., 303.

F. Fawcett, W., 355. Fischer, Hugo, 156. Fliche, P., 520, 521. Forbes, R. H., 219. Fortier, S., 194, 254. Fraenkel, L., 142. Frank, A., 151. Fuelles, P., 281. Furry, F. E., 73. Furuta, T., 383.

G. Geikie, J., 14. Gerlach, —, 156. Gilbert, G. K., 2. Gilbert, J. H., 151, 192. Godlewski, E., 337, 393 Goss, A., 376, 530. Grandeau, L., 132, 133, 139, 357, 520, 521.

H. Haberlandt, F., 310. Hall, A. D., 210, 227. Hare, R. F., 378. Harper, R. M., 494. Hartwell, B. L., 123. Headden, H. P., 18. Hedin, Sven, 9. Hellriegel, F., 130, 151, 192. Henrici, 200. Hillman, F. H., 536. Hiltner, L., 154. Hoffmann, R., 528. Hohl, J., 143. Hunt, T. S., 23.

J. Jaffa, M. E., 135, 381, 450, 530. Johnson, S. W., 60, 380.

K. Katayama, T., 383. Kearney, T. H., 532. Kedzie, R. C., 343, 375. Kellner, O., 393. King, F. H., 99, 108, 109, 168, 192, 193, 210, 211, 212, 224, 228, 236, 305, 325, 328, 332. Kinsley, J. S., 143. Knop, W., 197. Koch, R., 156, 281. Kossovitch, P., 363. Kosticheff, P., 130, 157. Kröber, 156. Krocker, F., 22. Kuntze, O., 67, 68.

L. Ladd, E. F., 131, 133, 134, 141. Langley, S. P., 288. Lawes, J., 151, 192. Lea, E. C., 387. Leather, J. W., 401, 410, 411, 412, 414 to 417, 440. Lemberg, J., 272 Lesage, M., 528. Letheby, H., 23. Liebig, J. von, 150, 313. Liebscher, G., 354. Lipman, J. G., 156. Loeb, J., 380. Loew, O., 23, 42, 382, 383. Loughridge, R. H., 87, 207, 213, 214, 240, 259, 340 to 342, 385, 430, 462, 466, 513, 535, 560.

M. Maercker, M., 65, 369. Mann, H. H., 401, 410, 413. Manson, M., 294. Maxwell, W., 339. May, D. W., 42, 380. Mayer, A., 199, 207, 209. Mayo, N. S., 143. Mazurenko, D. P., 87. Means, T. H., 248, 478. Merrill, G. P., 2, 13, 167. Middendorff, V., 441. Mitscherlich, E. A., 99, 199. Miquel, P., 142, 281, 359. Mohr, Chas., 489, 511. Moore, G. T., 154. Morck, D., 154. Müller, A., 449. Müller, P. E., 122, 184. Müntz, A., 142, 355, 370, 401, 402, 406 to 410. Murray, John, 23, 24. Myers, H. C., 6, 144.

N. Naegeli, C. v., 129. Nagaoka, M., 65, 393. Nobbe, F., 154.

O. Osterhout, W. J. V., 533. Ototzky, L., 265. Owen, D. D., 316, 317, 343, 513.

P. Peter, A. M., 175. Peter, R., 316,317, 343. Pichard, P., 147. Porter, J. L., 23, 24. Pumpelly, R., 110.

R. Rafter, G. W., 217. [204]Ramann, E. Reade, T. M., 41. Regnault, V., 26. Reichert, E., 276. Richthofen, F. von, 110. Risler, E., 354. Rosenberg, S., 528. Rousseaux, E., 355, 370, 401, 402, 406 to 410. Rudzinski, D., 87. Russell, I. C., 24.

S. Saussure, H. E. de, 150. Schimper, A. F. W., 523, 528. Schloesing, Th., 59, 111, 354. Schloesing, Th., fils, 332, 393. Schmidt, C., 23. Schöne, H. E., 90. Schübler, J. J., 116, 197, 313. Schultze, H., 328, 329. Seton, E. T., 159, 160. Shaler, N. S., 12. Shaw, G. W., 465. Smith, E. A., 511. Snyder, H., 131, 133, 134, 139. Stenhouse, —, 276. Stockbridge, H. E., 307, 308. Stone, C. H. H., 25. Stubenrauch, A. V., 222. Stutzer, A., 149.

T. Thurmann, J., 519, 520. Tolman, L. M., 387. Tourney, J. W., 216. Traphagen, F. W., 23. Tuxen, C. F. A., 184.

U. Udden, J. A., 106. Ulbricht, R., 328.

V. Vanderyst, H., 338. Ville, G., 151. Voelcker, J. A., 22, 410. Vogel, J. H., 156.

W. Wagner, P., 65. Ward, M., 144. Warington, R., 108, 146. Washington, H. S., xxiv. Way, J. T., 22, 73. Weber, A. H., 450. Wheeler, H. J., 123. Whitney, M., 94, 195, 207, 316, 321, 330, 332, 337. Wilfarth, H., 151. Williams, W. E., 60, 100. Winogradsky, S., 146, 156. Wohltmann, F., 355, 370, 401, 402 to 405, 406, 416. Wolff, E., 22, 73. Wollny, E., 110, 113, 125, 147, 159, 195, 264, 279, 281, 284, 305, 306. Wüllner, —, 198. Wunder, G., 327.

Y. Yoder, P. A., 92.

Z. Zöller, P. H., 22.

[204] This writer’s valuable “Boden Runde” (1905) unfortunately came to hand too late to be considered in this volume.

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