PROBLEMS OF DRY-FARMING 7 



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 impor- 

 tance 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 importance to the dry- 

 farmer, and they constitute another vital problem 

 of the science of dry-farming. 



The relation of crops to the prevailing conditions 



