Fig. 75.—Wheat grown on black alkali land at Tulare Substation, California,
showing improvement in successive years of reclamation treatment.
There is, however, a strong intrinsic reason pointing in the same direction, namely, the almost invariably high and lasting productiveness of these lands when once rendered available to agriculture. This is foreshadowed by the usually heavy and luxuriant growth of native plants around the margins and between alkali spots ([see fig. 60]); i. e., wherever the amount of injurious salts present is so small as not to interfere with the utilization of the abundant store of plant-food which, under the peculiar conditions of soil-formation in arid climates, remains in the land instead of being washed into the ocean. Extended comparative investigations of soil composition, as well as the experience of thousands of years in the oldest settled countries of the world, demonstrate this fact and show that so far from being in need of fertilization, alkali lands usually possess extraordinary productive capacity whenever freed from the injurious influence of the excess of useless salts left in the soil in consequence of deficient rainfall. (See analyses, chapter 22, pp. [436], [437]).
Fig. 76.—Grains grown on alkali land at Tulare Station, California.
Among many striking examples of the results of such reclamation, is that represented in the annexed [figure (75)], of grain grown on strong alkali land, before and after reclamation treatment. On the original land even “alkali weeds” would hardly grow; while afterward a wheat crop representing forty-two bushels per acre was grown. Additional illustrations are shown in the second [figure (76)], showing crops of wheat and barley as grown on partly reclaimed land at the Tulare substation.
While it is certainly true that when rightly treated, alkali lands can be rendered profusely and lastingly productive, yet close attention and constant vigilance are needed so long as the salts remain in the soil; and no one not determined to give such land such full attention, should undertake to cultivate it.
PART FOURTH.
SOILS AND NATIVE VEGETATION.
CHAPTER XXIV.
THE RECOGNITION OF CHARACTER OF SOILS FROM
THEIR NATIVE VEGETATION; MISSISSIPPI.[183]
Climatic and Soil-Conditions.—Next to climatic conditions, chief among which are temperature and moisture, the physical and chemical nature of the soil and subsoil is the most potent factor in determining the natural vegetation of any region. The limitations we observe in the adaptation of cultivated lands to certain crops, even with artificial help, must be much more strongly pronounced when no such aid is given, and the struggle for the survival of the fittest is continued, subject only to seasonal variations, for thousands of years. It is obvious that within the limits of the regional flora, the natural vegetation of any tract represents the best adaptation of plants to soils, in the results of long periods of the struggle for existence between competing species; the survivors being those best adapted to the entire environment.