These calculations are based upon the published average rainfall maps of the United States Weather Bureau.  In the far West, and especially over the so-called “desert” regions, with their sparse population, meteorological stations are not numerous, nor is it easy to secure accurate data from them.  It is strongly probable that as more stations are established, it will be found that the area receiving less than 10 inches of rainfall annually is considerably smaller than above estimated.  In fact, the United States Reclamation Service states that there are only 70,000,000 acres of desert-like land; that is, land which does not naturally support plants suitable for forage.  This area is about one third of the lands which, so far as known, at present receive less than 10 inches of rainfall, or only about 6 per cent of the total dry-farming territory.

In any case, the semiarid area is at present most vitally interested in dry-farming.  The sub-humid area need seldom suffer from drouth, if ordinary well-known methods are employed; the arid area, receiving less than 10 inches of rainfall, in all probability, can be reclaimed without irrigation only by the development of more suitable. methods than are known to-day.  The semiarid area, which is the special consideration of present-day dry-farming represents an area of over 725,000,000 acres of land.  Moreover, it must be remarked that the full certainty of crops in the sub-humid regions will come only with the adoption of dry-farming methods; and that results already obtained on the edge of the “deserts” lead to the belief that a large portion of the area receiving less than 10 inches of rainfall, annually, will ultimately be reclaimed without irrigation.

Naturally, not the whole of the vast area just discussed could be brought under cultivation, even under the most favorable conditions of rainfall.  A very large portion of the territory in question is mountainous and often of so rugged a nature that to farm it would be an impossibility.  It must not be forgotten, however, that some of the best dry-farm lands of the West are found in the small mountain valleys, which usually are pockets of most fertile soil, under a good supply of rainfall.  The foothills of the mountains are almost invariably excellent dry-farm lands.  Newell estimates that 195,000,000 acres of land in the arid to sub-humid sections are covered with a more or less dense growth of timber.  This timbered area roughly represents the mountainous and therefore the nonarable portions of land.  The same authority estimates that the desert-like lands cover an area of 70,000,000 acres.  Making the most liberal estimates for mountainous and desert-like lands, at least one half of the whole area, or about 600,000,000 acres, is arable land which by proper methods may be reclaimed for agricultural purposes.  Irrigation when fully developed may reclaim not to exceed 5 per cent of this area.  From any point of view, therefore, the possibilities involved in dry-farming in the United States are immense.