Horizontal Distribution of Alkali Salts in Arid Lands.—The constant occurrence of “alkali spots” in arid lands shows at once the great inequality of horizontal distribution of alkali impregnation. This is as prominent in level lands as on slopes, and in extremely arid regions it is mostly not possible to recognize even very considerable differences without close examination. Thus in lands appearing exactly alike on the surface, on the edge of the Salton basin in California, on the same forty acre 1.4% (56,000 pounds per acre) was found in the surface four feet at one point, and a hundred yards away, 12.5% (500,000 pounds). The mapping of alkali lands is therefore somewhat precarious unless carried into great detail. Moreover, it has been found that the location of the salts changes from year to year, especially in irrigated land, as might be expected. Those cultivating alkali lands have therefore to exercise constant watchfulness, unless the salts have been definitively eliminated by underdrainage over a considerable area; as merely local operations may be rendered ineffectual by the migration of the salts from neighboring tracts not reclaimed.
Alkali in Hill Lands.—As a rule, hill lands themselves are remarkably free from alkali, even in the arid regions; except when water is gathered in depressions, where strongly saline waters may be found in Washington, Montana and elsewhere. But on level plateau lands, where drainage is slow or imperfect, alkali appears as freely as it does in the same regions in the stream bottoms. In the latter the leachings and seepage of the uplands naturally causes a concentration of the salts, and thus we find alkali salts incrusting the surface in the valleys of the streams, as e. g., that of the Yellowstone, Musselshell, Judith, Yakima and others in the north, and of Green river, Platte, Pecos, and Rio Grande farther south; as well as in numerous valleys of central and southern California.
Usar Lands of India.—These lands have been investigated first by the “Reh Commission” appointed to investigate the causes of the deterioration of lands in the Aligarh district (south of Delhi, between the Ganges and Jumna rivers), in 1876. The occasion of this appointment was the appearance of “reh” (alkali salts) in a region which had previously been free from them.[166] Subsequently, a more elaborate investigation of the subject was made by Dr. J. W. Leather, Agricultural Chemist to the Government of India.[167] From these documents it appears that “usar lands” exist largely not only in the Northwestern Provinces and Oudh, but also in the Panjab, especially on the lands bordering the Chenab river; likewise to a slight extent in the Bombay presidency. Leather’s investigation shows that not all the lands designated by the natives as usar contain soluble salts in injurious amounts, some being simply lands having very hard, clayey soils difficult to till with the imperfect methods employed. Yet the general phenomena of the true “reh” lands are practically identical with those of the American alkali lands, including also the calcareous hardpan, there called kankar. Owing probably to the long cultivation of the Indian lands (mostly under irrigation), the salts are there at their maximum in the first foot, decreasing as depth increases. It is noteworthy also that in the majority of cases the predominant salt is carbonate of soda or black alkali, which there as in California renders the lands impervious to water until treated with gypsum. This fact accounts for the popular use of the same name for non-saline impervious clay soils, and the alkali or reh lands proper.
We have an entirely analogous case in the “Szek” lands of the Hungarian plain, some of which are simply poor refractory soils containing a trace of soluble salts; while lower down in the valley of the Theiss we find genuine alkali lands, both black and white, which have long furnished carbonate of soda for local use and commerce. In this case, however, the alkali salts seen to come largely, in some cases wholly, from underlying saline clays whose salts in coming to the surface suffer precisely the same transformations experienced in California and India, in presence of calcic carbonate ([see below, p. 450 ff]).
The accounts given by v. Middendorff of the nature and occurrence of alkali lands in Turkestan (Ferghana) agree entirely with those given above for California and India; as do also the investigations made by other Russian observers on the saline lands of the steppes of European Russia.
COMPOSITION AND QUANTITY
OF ALKALI SALTS.
Black and White Alkali.—Broadly speaking, the world over alkali salts consist mainly of three chief ingredients, already mentioned, namely, common salt, Glauber’s salt (sulfate of soda), and salsoda or carbonate[168] of soda. The latter causes what is popularly known as “black alkali,” from the black spots of puddles seen on the surface of lands tainted with it, owing to the dissolution of the soil humus;[169] while the other salts, often together with Epsom salt and bittern (Magnesium chlorid), constitute “white alkali,” which is known to be very much milder in its effect on plants than the black. In most cases all three are present, and all may be considered as practically valueless, or noxious, to plant growth.
| EUROPE. | ASIA | |||||
|---|---|---|---|---|---|---|
| Hungarian Plain. “Szekso.” | Aralo-Caspian Plain. Saline Crusts. | Aden. “Hurka” “Kara.” | ||||
| Debreczin | Kalocsa | |||||
| Potassium Sulfate (K₂SO₄) | ||||||
| Sodium Sulfate (Na₂SO₄) | .2 | 1.6 | 10.4 | 18.2 | 15.5 | |
| Sodium Carbonate (Na₂CO₃) | 48.1 | 92.5 | 14.7 | 12.1 | 69.0 | 67.2 |
| Sodium Chlorid (NaCl) | 51.7 | 4.4 | 74.6 | 69.7 | 15.5 | 32.8 |
| Sodium Phosphate (Na₃PO₄) | ||||||
| Calcium Chlorid | ||||||
| Magnesium Chlorid (MgCl₂) | ||||||
| 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | |
| ASIA | ||||
|---|---|---|---|---|
| India “Reh.” | ||||
| Gursikar, Aligarh, 6 feet. | Jellalabad, Panjab, 1.5 feet. | Bayamati (Regur), Deccan, 2 feet. | ||
| Potassium Sulfate (K₂SO₄) | 11.1 | |||
| Sodium Sulfate (Na₂SO₄) | 7.0 | 15.5 | 58.5 | 2.3 |
| Sodium Carbonate (Na₂CO₃) | 79.0 | 56.9 | 22.9 | |
| Sodium Chlorid (NaCl) | 2.9 | 27.6 | 18.6 | 97.7 |
| Sodium Phosphate (Na₃PO₄) | ||||
| Calcium Chlorid | ||||
| Magnesium Chlorid (MgCl₂) | ||||
| 100.0 | 100.0 | 100.0 | 100.0 | |
| AFRICA. | ||||
|---|---|---|---|---|
| Egypt | Fezzan Trona, (Commercial.) | |||
| Trona, (Commercial.) | Alkali L. Abukir. | |||
| Potassium Sulfate (K₂SO₄) | 6.49 | |||
| Sodium Sulfate (Na₂SO₄) | 23.6 | 38.3 | .82 | 0.6 |
| Sodium Carbonate (Na₂CO₃) | 28.2 | 47.7 | 1.13 | 98.7 |
| Sodium Chlorid (NaCl) | 48.2 | 14.0 | 89.74 | .7 |
| Sodium Phosphate (Na₃PO₄) | ||||
| Calcium Chlorid | 1.82 | |||
| Magnesium Chlorid (MgCl₂) | ||||
| 100.0 | 100.0 | 100.0 | 100.0 | |