As has been stated elsewhere, any rotation in dry-farming which does not include the summer fallow at least every third or fourth year is likely to be dangerous In years of deficient rainfall.

This review of the question of dry-farm fertility is intended merely as a forecast of coming developments.  At the present time soil-fertility is not giving the dry-farmers great concern, but as in the countries of abundant rainfall the time will come when it will be equal to that of water conservation, unless indeed the dry-farmers heed the lessons of the past and adopt from the start proper practices for the maintenance of the plant-food stored in the soil.  The principle explained in Chapter IX, that the amount of water required for the production of one pound of water diminishes as the fertility increases, shows the intimate relationship that exists between the soil-fertility and the soil-water and the importance of maintaining dry-farm soils at a high state of fertility.

CHAPTER XV

IMPLEMENTS FOR DRY-FARMING

Cheap land and relatively small acre yields characterize dry-farming.  Consequently Iarger areas must be farmed for a given return than in humid farming, and the successful pursuit of dry-farming compels the adoption of methods that enable a man to do the largest amount of effective work with the smallest expenditure of energy.  The careful observations made by Grace, in Utah, lead to the belief that, under the conditions prevailing in the intermountain country, one man with four horses and a sufficient supply of machinery can farm 160 acres, half of which is summer-fallowed every year; and one man may, in favorable seasons under a carefully planned system, farm as much as 200 acres.  If one man attempts to handle a larger farm, the work is likely to be done in so slipshod a manner that the crop yield decreases and the total returns are no larger than if 200 acres had been well tilled.

One man with four horses would be unable to handle even 160 acres were it not for the possession of modern machinery; and dry-farming, more than any other system of agriculture, is dependent for its success upon the use of proper implements of tillage.  In fact, it is very doubtful if the reclamation of the great arid and semiarid regions of the world would have been possible a few decades ago, before the invention and introduction of labor-saving farm machinery.  It is undoubtedly further a fact that the future of dry-farming is closely bound up with the improvements that may be made in farm machinery.  Few of the agricultural implements on the market to-day have been made primarily for dry-farm conditions.  The best that the dry-farmer can do is to adapt the implements on the market to his special needs.  Possibly the best field of investigation for the experiment stations and inventive minds in the arid region is farm mechanics as applied to the special needs of dry-farming.