Crop-producing power of rainfall
If this conclusion, that not more than 750 pounds of water are
required under ordinary dry-farm conditions for the production of
one pound of dry matter, be accepted, certain interesting
calculations can be made respecting the possibilities of
dry-farming. For example, the production of one bushel of wheat will
require 60 times 750, or 45,000 pounds of water. The wheat kernels,
however, cannot be produced without a certain amount of straw, which
under conditions of dry-farming seldom forms quite one half of the
weight of the whole plant. Let us say, however, that the weights of
straw and kernels are equal. Then, to produce one bushel of wheat,
with the corresponding quantity of straw, would require 2 times
45,000, or 90,000 pounds of water. This is equal to 45 tons of water
for each bushel of wheat. While this is a large figure, yet, in many
localities, it is undoubtedly well within the truth. In comparison
with the amounts of water that fall upon the land as rain, it does
not seem extraordinarily large.
One inch of water over one acre of land weighs approximately 226,875
pounds.
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