450 
Journal of Agricultural Research 
Vol. VII, No. io 
20 days with seven velocities. In each case there was an alley where the 
air was kept quiet. The combined results of the two tests are shown in 
figure 6. There is a rapid increase in evaporation with increased wind 
velocity at first; but after a velocity of about io miles per hour is reached, 
the increase in evaporation is slight. The water loss with the highest 
velocity was over four times that of the calm for the 16-day trial and 
nearly six times that of the calm in the 20-day test. 
sunshine 
The general effect of sunshine in increasing the evaporation of soil 
moisture has long been known. The work of Seelhorst and Widtsoe on 
this subject has already been reviewed. In order to get more data an 
experiment was begun in the summer of 1913 at the Utah Agricultural 
Experiment Station. 
A spot on the college 
lawn just west of the 
main building was se¬ 
lected, because it was 
level and exposed to 
sunshine most of the 
day. 
Small tin plates con¬ 
taining 100 gm. dry 
weight of Greenville 
loam were prepared by 
puddling the soil and 
then drying, in order 
to get uniformity. 
They were then made 
up to the desired de¬ 
gree of wetness—5, 10, 15, 20, and 25 per cent, respectively. Each 
treatment was run in triplicate, making 15 pans to the set. One set 
was exposed to open sunshine, another was placed under a shade of 
cheesecloth 8 inches above the soil, and a third was shaded by a tight 
board cover also 8 inches above the soil. In each case the pans of soil 
were placed on a floor of boards and air was allowed to circulate freely 
over the soil beneath the cover. 
5 to 15 T3 
Wind Velocity In Miles Per Hour 
Fig. 6.—Evaporation of water from wet soils with different wind 
velocities. 
The pans were each morning made up in the laboratory to the proper 
wetness and carried outside. Temperature readings were taken in the 
morning when the pans were carried out by laying a tested thermometer 
for a few minutes between the pans. A reading was taken at noon and 
another in the afternoon just before the pans were carried back into the 
laboratory. Another weighing of the pans showed the recorded loss due 
to evaporation. The pans were then left over night to be made up in 
the morning before placing outside. 
