210 
Journal of Agricultural Research 
VoL VII, No. 4 
error, and the correlations are substantially in accord with those pre¬ 
viously determined. 
Tabl 3 XXV .—Comparison of correlations obtained by the two methods of correcting for 
the march in the transpiration coefficient , Kubanka wheat , 1914 
Factor 
First method 
Second method 
Transpiration and evaporation: 
Shallow tank. 
0. 85 ±0.03 
. j 6 ± . 04 
. 64 i « 06 
. 72 i .05 
. 88± . 02 
. 26± . 09 
O. 83 ±0. 03 
. 67 ± .06 
• 77 ± -03 
. 62 ± .07 
. 79 ± • 04 
. 27± . 10 
Deep tank. 
Transpiration and radiation.. 
Transpiration and temperature. 
Transpiration and wet-bulb depression. 
Transpiration and wind velocity. 
SUMMARY 
The transpiration studies included in this paper were made at Akron, 
Colo., during the summers of 1914 and 1915. 
The plants were grown in large pots (115 kgm. of soil) and sealed to 
prevent evaporation from the soil surface. 
The pots were weighed each morning before the transpiration response 
to sunlight had set in. 
Six pots of each crop were used in the determinations, and were weighed 
too. 1 kgm. 
Twenty-two crops (132 pots) were included in the 19x4 measurement 
and 23 crops (138 pots) in 1915. 
Continuous automatic records were also obtained of air temperature, 
solar radiation, wet-bulb depression, wind velocity, evaporation from a 
shallow tank, and evaporation from a deep tank. 
The climatic conditions were exceptionally uniform throughout the 
season of 1914. The summer of 1915 was unusually rainy. 
During a 10-day period of maximum transpiration the annual crops 
lost about one-fourth of the total water lost during the season. The 
alfalfas lost during this period almost one-half of the total water trans¬ 
pired in the production of the second crop. 
During a 10-day period of maximum transpiration the daily loss of 
water from the small grains ranged from 12 to 16 times the dry weight 
of the crop; millets, corn, and sorghums, 6 to 9 times; and alfalfas, 36 to 
56 times the dry weight harvested. On the basis of a production of 1 ton 
of dry matter per acre, this would correspond in the case of the small 
grains to a daily loss of 0.11 to 0.14 acre-inch of water; corn, millet, and 
sorghum, 0.05 to 0.08 acre-inch; and alfalfas, 0.32 to 0.49 acre-inch. 
The loss of water from the small grains during the period of maximum 
transpiration amounted to 1.5 kgm. per square meter of plant surface 
per day; Sudan grass, 0.8 kgm; and alfalfa, 1.6 kgm. This is from 5 to 14 
per cent of the loss during the same period from a free water surface of 
equal area. 
