BROOM-CORX EXPERIMENTS AT WOODWARD, OKLAHOMA. 9 



for the entire day. Such high winds may cause great damage 

 either by covering up the young plants, by cutting them off with 

 moving particles of soil, or by blowing down the crop when it is 

 approaching maturity. 



Temperature. 



The daily range in temperature is large. In summer the days are 

 warm to hot, but the nights usually are cool. The data on mean, 

 maximum, and minimum temperatures and the dates, by months, for 

 the season (April to September) in the 5-year period from 1914 to 

 1918, inclusive, are given in Table III, which also contains data on 

 wind movement. 



The temperature in winter seldom reaches zero, but occasionally 

 even lower temperatures occur. In summer the temperature reaches 

 the 100° F. mark and above quite frequently. The maximum 

 temperature in this 5-year period, 109° F., was recorded on several 

 dates in June, 1917. The average date of the last spring frost is 

 April 11, and that of the first fall frost, October 25, leaving an 

 average frost-free period of 196 days. 



Evaporation. 



In the district here described the loss of moisture by evaporation 

 is very great. The chief factors that influence evaporation are pre- 

 cipitation, wind, and temperature. The maximum evaporation 

 naturally occurs in periods of high temperatures, low rainfall, and 

 strong winds. 



Table IV. — Monthly seasonal and average monthly precipitation- and evapora- 

 tion at the Woodward (Okla.) Field Station during the six months from April 

 to September, inclusive, in the 5-year period from 1914 to 1918, inclusive. 



[Data <in inches) furnished by the Office of Biophysical Investigations, Bureau of Plant Industry.] 





April. 



Hay. 



June. 



July. 



August. 



September. 



Total. 



Year. . 



Pre- 

 cipi 



ta- 

 tion. 



Evap- 

 ora- 

 tion. 



"Pre- 



Clpl- 



ta- 

 tion. 



Evap- 

 ora- 

 tion. 



Pre- 



cipi- 



ta- 



tion. 



Evap- 

 ora- 

 tion. 



Pre- 

 cipi- 



ta- 

 tion. 



Evap- 

 ora- 

 tion. 



Pre- 

 cipi- 



ta- 

 tion. 



Evap- 

 ora- 

 tion. 



Pre- 

 cipi- 



ta- 

 tion. 



Evap- 

 ora- 

 tion. 



Pre- 

 cipi- 



ta- 

 tion. 



Evap- 

 ora- 

 tion. 



1914 



1.7 



6.5 

 2.3 

 1.6 



2 2 



6.8 

 6.0 

 6.0 

 7.2 

 5.0 



3.2 

 5.3 

 1.7 

 1.0 



4.0 



6.2 

 6.7 

 9.8 

 7.0 

 9.3 



0.6 

 2.4 

 10.3 

 1.4 

 1.9 



11.3 

 6.6 

 7.7 



11.3 

 8.7 



1.9 

 3.1 







1.1 

 .7 



10.9 

 10.0 

 10.4 

 11.7 

 10.1 



2.6 

 3.6 

 1.0 



6.9 

 1.3 



8.9 

 6.5 



11.2 

 7.4 



11.0 



0.6 

 5.7 

 2.3 

 2.0 

 1.2 



8.4 

 5.8 

 7.5 

 5.0 

 5.8 



10.5 

 26. S 

 17.6 

 14.0 

 11.3 



52.6 



191-5 



41.7 



1916 



1917 



52.6 

 49.6 



1918 



49.9 







Average 



2.9 



6.2 



3.0 



7.8 



3.3 



9.1 



1.4 



10.6 



3.1 



8.0 



2.4 



6.5 



l-J.O 



4. 3 



Table IV contains a comparison of the monthly precipitation and 



evaporation records made at the Woodward Field Station during 



the six months from April to September in each year of the 5-year 



period from 1914 to 1918, inclusive. The evaporation measured is 



147841°— 20— Bull. 836 2 



