20 DRY-FARMING 
fall, which up to the present seems to be the lower 
limit of successful dry-farming, there is a maximum 
possibility of producing 25 bushels of wheat annually. 
In the subjoined table, constructed on the basis 
of the discussion of this chapter, the wheat-produc- 
ing powers of various degrees of annual precipita- 
tion are shown : — 
One acre inch of water will produce 23} bushels of wheat. 
Ten acre inches of water will produce 25 bushels of wheat. 
Fifteen acre inches of water will produce 374 bushels of 
wheat. 
Twenty acre inches of water will produce 50 bushels of 
wheat. 
It must be distinctly remembered, however, that 
under no known system of tillage can all the water 
that falls upon a soil be brought into the soil and 
stored there for plant use. Neither is it possible to 
treat a soil so that all the stored soil-moisture may 
be used for plant production. Some moisture, of 
necessity, will evaporate directly from the soil, and 
some may be lost in many other ways. Yet, even 
under a rainfall of 12 inches, if only one half of the 
water can be conserved, which experiments have 
shown to be very feasible, there is a possibility of 
producing 30 bushels of wheat per acre every other 
year, which insures an excellent interest on the 
money and labor invested in the production of the 
crop. 
