Transpiration as a Factor in Crop Production. 107 
In a normal year the period from July 10 to August 20 is the 
most critical in corn production under Nebraska conditions, 
which may be ascribed to the high transpiration rate due to the 
combined high evaporating power of the atmosphere and the 
maximum leaf development of the plant. This is aside from the 
occasional blasting of the pollen and consequent reduction in 
grain development. Table 32 and Chart XVII show the tran- 
spiration by the week thruout the season for each of four degrees 
of soil moisture as tested in 1914. 
Mb- 
grams 
25 
20 
JS 
10 
S 
,. Wk/fo.. 
/ * 
-H- 
11/ 
v~ 
r 
*— 
v \ 
rrt~ 
1 z 
r -< 
1 
t t 
> 
r "< 
i — i 
1 — 7 
-55 % &ff7V/V?T/QJY -50% SOU SfiTC/ffJT/O/Y 
70 % SO/Z SrfTUMUOff %o/yo% SOU SJm/fMTIO/i 
Chart XVII. — Weekly transpiration thruout the life of plants growing in 
different degrees of soil-moisture content. 1914. (Graph of Table 32.) 
VARIATION IN YEARLY TRANSPIRATION. 
As was seen in Table 31, the climatic conditions prevailing in 
July and August are the determining factors in the yield of corn, 
so far as transpiration is concerned. In 1914, 86 per cent of the 
entire transpiration from corn occurred during July and August. 
Accordingly, in an attempt to correlate the seasonal transpiration 
with evaporation and the climatic factors, during the five con- 
