This brief review shows that, everything considered, arid soils are superior to humid soils.  In ease of handling, productivity, certainty of crop-lasting quality, they far surpass the soils of the countries in which scientific agriculture was founded.  As Hilgard has suggested, the historical datum that the majority of the most populous and powerful historical peoples of the world have been located on soils that thirst for water, may find its explanation in the intrinsic value of arid soils.  From Babylon to the United States is a far cry; but it is one that shouts to the world the superlative merits of the soil that begs for water.  To learn how to use the “desert” is to make it “blossom like the rose.”

Soil divisions

The dry-farm territory of the United States may be divided roughly into five great soil districts, each of which includes a great variety of soil types, most of which are poorly known and mapped.  These districts are:—­

1.  Great Plains district. 2.  Columbia River district 3.  Great Basin district. 4.  Colorado River district. 5.  California district.

Great Plains district.—­On the eastern slope of the Rocky Mountains, extending eastward to the extreme boundary of the dry-farm territory, are the soils of the High Plains and the Great Plains.  This vast soil district belongs to the drainage basin of the Missouri, and includes North and South Dakota, Nebraska, Kansas, Oklahoma, and parts of Montana, Wyoming, Colorado, New Mexico, Texas, and Minnesota.  The soils of this district are usually of high fertility.  They have good lasting power, though the effect of the higher rainfall is evident in their composition.  Many of the distinct types of the plains soils have been determined with considerable care by Snyder and Lyon, and may be found described in Bailey’s “Cyclopedia of American Agriculture,” Vol.  I.

Columbia River district.—­The second great soil district of the dry-farming territory is located in the drainage basin of the Columbia River, and includes Idaho and the eastern two thirds of Washington and Oregon.  The high plains of this soil district are often spoken of as the Palouse country.  The soils of the western part of this district are of basaltic origin; over the southern part of Idaho the soils have been made from a somewhat recent lava flow which in many places is only a few feet below the surface.  The soils of this district are generally of volcanic origin and very much alike.  They are characterized by the properties which normally belong to volcanic soils; somewhat poor in lime, but rich in potash and phosphoric acid.  They last well under ordinary methods of tillage.

The Great Basin.—­The third great soil district is included in the Great Basin, which covers nearly all of Nevada, half of Utah, and takes small portions out of Idaho, Oregon, and southern California.  This basin has no outlet to the sea.  Its rivers empty into great saline inland lakes, the chief of which is the Great Salt Lake.  The sizes of these interior lakes are determined by the amounts of water flowing into them and the rates of evaporation of the water into the dry air of the region.