16 DRY-FARMING 
results tend to be somewhat higher than those ob- 
tained 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 inereases 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-farm- 
ing is likely to be practiced, a moderately high tem- 
perature, 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 mat- 
ter 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 . .... ee ee ee (1048 
"Com 20406 6 ee Rowe we wow ws « 9bBd 
Peds: a eG ee Se wee ok ot ES 
Sugar beets. . . . . ~~... . 630 
These Utah findings support strongly the doctrine 
that the amount of water required for the produc- 
