CEREAL INVESTIGATIONS ON THE BELLE FOURCHE FARM. 7 
TaBLE IV.— Monthly precipitation and evaporation from a free water surface at the Belle 
Fourche Experiment Farm, by months, from April to July of each year, 1908 to 1913, 
inclusive. 
[Data (in inches) from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 
April. | May. | June. July. Total. 
Year. ae sie ae ; | Ratio. 
Precipi-| Evapo-|Precipi-; Evapo-| Precipi-| Evapo-| Precipi-| Evapo-|Precipi-| Evapo- 
tation. | ration. | tation. | ration. | tation. | ration. | tation. | ration. | tation. | ration. 
Oe cosadsc D165 |\e os030 3.95 | 5.917 1.47 | 6.821 1.26} 8.081 7.84 | 26.354 | 1: 3.36 
Eas osece .84 | 3.657 3.87 | 6.413 5.59 | 5.859 2:40) i) (698: | L2n75l 235627) places 
OO) seeeear 1.57 | 5.408 1265 |) 5-306 1.51 | 8.975 1.42 | 10.429 D516 SOIT Sales 23 
LOUIS RE Sees .17 | 4.649 .45 | 8.302 -50 | 10.241 .80 | 10.714 1.92 | 33.906 | 1-17.66 
IO Eaeoaas 2.32 | 4.849 2.26 | 6.423 200) 2 Se75 3.20 | 7.980 8.07 | 27.427 |1: 3.40 
IG eoagemee -25 | 4.705 1.98 | 4.302 3.10 | .7.046 sets) | TEE PRS 5.68.| 24.288 |1: 4.26 
Average.| 1.05 | 4.801 2.29 | 6.110 2.08 | -7.853 1.58 | 8.856 7.00 | 27.620 | 1:3.95 
The ratio of precipitation to evaporation, also given in Table IV, 
shows the evaporation for the six years to be 3.95 times the precipita- 
tion. In 1909 the ratio was the narrowest, the evaporation for that 
- year being only 1.85 times the precipitation. In 1911 the ratio was 
the widest, the evaporation being 17.66 times the precipitation. ‘The 
ratios of precipitation to evaporation for the different years compared 
with the average ratio for the entire period afford an excellent basis 
for judging the seasonal conditions under which the experiments re- 
ported in this bulletin were conducted. 
WIND. 
The record of wind measurements has been taken at the Belle 
Fourche Experiment Farm during the growing season since May, 
1909. The anemometer stands near the evaporation tank, at a height 
of about 2 feet from the surface of the ground. The average wind 
velocities in miles per hour during the months from April to July for 
the years 1908 to 1913, inclusive, are presented in Table V. 
TaBLeE V.—Average wind velocity at the Belle Fourche Experiment Farm, by months, 
from April to July of each year, 1908 to 1913, inclusive. 
[Data (in miles per hour) from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 
Month. 1908 1909 | 1910 1911 1912 1913 | Average. 
PAC RUE Aaa fae Masher Sense ew eles ee sa ee 9.1 9.2 9. 2 9.5 6. 2 8.6 
Nae Cree 8.3 10.1 8.2 11.6 1 5.9 9.2 
TE pore eee ee ee 7.2 6.2 9.3 9.1 7.6 6.8 TE 
Tuitves Sek oie eee 5.0 6.0 7.7 7.9 6.0 5.8 6.5 
iReetapenmae oi oo ks tuol. 6.8 7.8 8.6 | 9.5 8.6 6.2 8.0 
Table V shows the average wind velocity at Newell to be 8 miles 
per hour from April 1 to July 31. The greatest average wind velocity, 
9.2 miles per hour, is for the month of May. In June and July there 
is a considerable decrease in the velocity of the wind, the average for 
4506°—Bull: 297—15——2 
