dry-farming, and the firm establishment of right methods of
conserving and using the natural precipitation will undoubtedly have
a beneficial effect upon the practice of humid agriculture.

The problems of dry-farming

The dry-farmer, at the outset, should know with comparative accuracy
the annual rainfall over the area that he intends to cultivate. He
must also have a good acquaintance with the nature of the soil, not
only as regards its plant-food content, but as to its power to
receive and retain the water from rain and snow. In fact, a
knowledge of the soil is indispensable in successful dry-farming.
Only by such knowledge of the rainfall and the soil is he able to
adapt the principles outlined in this volume to his special needs.

Since, under dry-farm conditions, water is the limiting factor of
production, the primary problem of dry-farming is the most effective
storage in the soil of the natural precipitation. Only the water,
safely stored in the soil within reach of the roots, can be used in
crop production. Of nearly equal importance is the problem of
keeping the water in the soil until it is needed by plants. During
the growing season, water may be lost from the soil by downward
drainage or by evaporation from the surface. It becomes necessary,
therefore, to determine under what conditions the natural
precipitation stored in the soil moves downward and by what means
surface evaporation may be prevented or regulated. The soil-water,
of real use to plants, is that taken up by the roots and finally
evaporated from the leaves. A large part of the water stored in the
soil is thus used. The methods whereby this direct draft of plants
on the soil-moisture may be regulated are, naturally, of the utmost