Dry-Farming | Page 4

Hellriegel, and Sorauer, in the early eighties of the last century. In
every case, the numbers in the table represent the number of pounds of
water used for the production of one pound of ripened dry substance:
Pounds Of Water For One Pound Of Dry Matter
Wollny Hellreigel Sorauer Wheat 338 459 Oats 665 376 569 Barley
310 431 Rye 774 353 236 Corn 233 Buckwheat 646 363 Peas 416 273
Horsebeans 282 Red clover 310 Sunflowers 490 Millet 447
It is clear from the above results, obtained in Germany, that the amount
of water required to produce a pound of dry matter is not the same for
all plants, nor is it the same under all conditions for the same plant. In
fact, as will be shown in a later chapter, the water requirements of any
crop depend upon numerous factors, more or less controllable. The
range of the above German results is from 233 to 774 pounds, with an
average of about 419 pounds of water for each pound of dry matter
produced.
During the late eighties and early nineties, King conducted experiments
similar to the earlier German experiments, to determine the water

requirements of crops under Wisconsin conditions. A summary of the
results of these extensive and carefully conducted experiments is as
follows:--
Oats 385 Barley 464 Corn 271 Peas 477 Clover 576 Potatoes 385
The figures in the above table, averaging about 446 pounds, indicate
that very nearly the same quantity of water is required for the
production of crops in Wisconsin as in Germany. The Wisconsin
results tend to be somewhat higher than those obtained in Europe, but
the difference is small.
It is a settled principle of science, as will be more fully discussed later,
that the amount of water evaporated from the soil and transpired by
plant leaves increases materially with an increase in the average
temperature during the growing season, and is much higher under a
clear sky and in districts where the atmosphere is dry. Wherever
dry-farming is likely to be practiced, a moderately high temperature, a
cloudless sky, and a dry atmosphere are the prevailing conditions. It
appeared probable therefore, that in arid countries the amount of water
required for the production of one pound of dry matter would be higher
than in the humid regions of Germany and Wisconsin. To secure
information on this subject, Widtsoe and Merrill undertook, in 1900, a
series of experiments in Utah, which were conducted upon the plan of
the earlier experimenters. An average statement of the results of six
years' experimentation is given in the subjoined table, showing the
number of pounds of water required for one pound of dry matter on
fertile soils:--
Wheat 1048 Corn 589 Peas 1118 Sugar Beets 630

These Utah findings support strongly the doctrine that the amount of
water required for the production of each pound of dry matter is very
much larger under arid conditions, as in Utah, than under humid
conditions, as in Germany or Wisconsin. It must be observed, however,
that in all of these experiments the plants were supplied with water in a
somewhat wasteful manner; that is, they were given an abundance of
water, and used the largest quantity possible under the prevailing
conditions. No attempt of any kind was made to economize water. The
results, therefore, represent maximum results and can be safely used as
such. Moreover, the methods of dry-farming, involving the storage of

water in deep soils and systematic cultivation, were not employed. The
experiments, both in Europe and America, rather represent irrigated
conditions. There are good reasons for believing that in Germany,
Wisconsin, and Utah the amounts above given can be materially
reduced by the employment of proper cultural methods.
The water in the large bottle would be required to produce the grain in
the small bottle.
In view of these findings concerning the water requirements of crops, it
cannot be far from the truth to say that, under average cultural
conditions, approximately 750 pounds of water are required in an arid
district for the production of one pound of dry matter. Where the aridity
is intense, this figure may be somewhat low, and in localities of
sub-humid conditions, it will undoubtedly be too high. As a maximum
average, however, for districts interested in dry-farming, it can be used
with safety.
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