CEREAL INVESTIGATIONS ON THE BELLE FOUECHE 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.B 



ophysical Laboratory of the Bureau of Plant Industry.] 





April. 



May. 



June. 



July. 



Total. 





Year. 



Precipi- 

 tation. 



Evapo- 

 ration. 



Precipi- 

 tation. 



Evapo- 

 ration. 



Precipi- 

 tation. 



Evapo- 

 ration. 



Precipi- 

 tation. 



Evapo- 

 ration. 



Precipi- 

 tation. 



Evapo- 

 ration. 



Ratio. 



1908 



1909 



1910 



1911 



1912 



1913 



1.16 

 .84 



1.57 

 .17 



2.32 

 .25 



5.535 

 3. 657 



5.408 

 4.649 

 4.849 

 4.705 



3.95 

 3.87 

 1.26 

 .45 

 2.26 

 1.98 



5.917 

 6.413 

 5.306 

 8.302 

 6.423 

 4.302 



1.47 

 5.59 

 1.51 

 .50 

 .29 

 3.10 



6.821 

 5.859 

 8.975 

 10. 241 

 8.175 

 7.046 



1.26 

 2.45 

 1.42 



.80 

 3.20 



.35 



8.081 

 7.698 

 10. 429 

 10.714 

 7.980 

 8. 235 



7.84 

 12.75 

 5.76 

 1.92 

 8.07 

 5.68 



26. 354 

 23. 627 

 30. US 

 33. 906 



27. 427 

 24. 288 



1: 3.36 

 1: 1.85 

 1: 5.23 

 1 ■ 17. 66 

 1: 3.40 

 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 

 forjudging the seasonal conditions under which the experiments re- 

 ported in this bulletin were conducted. 



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. 



Table 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. 







9.1 



10.1 



6.2 



6.0 



9.2 

 8.2 

 9.3 



7.7 



9.2 

 11.6 

 9.1 



7.9 



9.5 

 11.1 



7.6 

 6.0 



6.2 

 5.9 

 6.8 

 5.8 



8.6 





8.3 

 7.2 

 5.0 



9.2 





7.7 





6.5 









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 



