CEREALS O:^ THE BELLE FOURCHE EXPERIMENT FARM. 



9 



The ratio of precipitation to evaporation, also given in Table II, 

 shows the evaporation for the 12 years to be 3.5 times the precipi- 

 tation. In 1915 the ratio was the narrowest, the evaporation for that 

 year being only 1.6 times the precipitation. In 1911 the ratio was the 

 widest, the evaporation being 9.9 times the precipitation. The ratio 

 of precipitation to evaporation is a fair indication of the seasonal 

 moisture conditions as related to crop yields. 



WIND. 



The record of wind measurement 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 six months from April to Sep- 

 tember for the years 1908 to 1919, inclusive, are presented, in 

 Table III. 



Table III. — Average wind velocity at the Belle Foiirche Experiment Farm for 

 the six months from April to September, during the 12-year period from 1908 

 to 1919, inclusive. 



[Data in miles per hour.] 



Month. 



1908 



1909 



1910 



1911 



1912 



1913 



1914 



1915 



1916 



1917 



1918 



1919 



Aver- 

 age. 



April 





9.1 

 10.1 

 6.2 

 6.0 

 5.6 

 5.7 



9.2 



8.2 

 9.3 

 7.7 

 6.6 

 6.2 



9.2 

 11.6 

 9.1 

 7.9 

 7.3 

 7.9 



9.5 

 11.1 

 7.6 

 6.0 

 6.9 

 7.6 



6.2 

 5.9 



6.8 

 5.8 

 5.1 

 4.5 



8.2 

 7.7 

 6.7 

 5.0 

 5.0 

 6.2 



6.6 

 7.4 

 6.2 

 5.0 

 4.1 

 5.9 



7.8 

 8.7 

 7.3 

 5.1 

 4.4 

 6.2 



7.8 

 5.7 

 6.3 

 5.3 

 4.2 

 5.1 



9.2 

 6.6 



4.5 

 4.2 



2.8 

 2.2 



7.4 

 7.3 

 7.7 

 6.7 

 5 8 

 5.5 



8.2 



May 



8.3 

 7.2 

 5.0 

 6.8 

 6.5 



8.2 



June 



7.1 



July 



5.8 





5.4 



September 



5.8 







Average 



6.8 



7.1 



7.9 



8.8 



8.1 



5.7 



6.5 



5.9 



6.6 



5.7 



4.9 



6.7 



6.8 







The average wind velocity during this period was 6.8 miles per 

 hour. The highest average wind velocity, 8.8 miles per hour, was 

 recorded in 1911, while the lowest, 4.9 miles per hour, was observed 

 in 1918. The velocity during April, May, and June was consider- 

 ably higher than in July, August, and September. The velocity of 

 the wind has a decided influence upon the crops. The evaporation 

 from the surface of the soil or plant is greatly increased by wind. 

 Hot winds, such as occurred in 1914 and 1917, caused the cereal 

 plants to be prematurely ripened or deadened before the grain was 

 fully developed. Winter wheat was injured somewhat nearly every 

 spring by the blowing of the soil before the spring rains had mois- 

 tened it. In 1916 some of the spring grains had to be resown be- 

 cause of being blown out after emergence. Owing to the high wind 

 velocity in the early spring, together with the tendency of the soil 

 to blow at that time, it was necessary practically to discontinue sum- 

 mer fallowing as a preparation for grain crops. 

 77754°— 22 2 



