6 



BULLETIN" 402, U. S, DEPARTMENT OP AGEICULTTJRE. 



inches in 1915. The seasonal precipitation has been closely corre- 

 lated with the yield in bushels per acre. The average precipitation, 

 as computed from records of the 11 years, will probably be reduced 

 when the records from a longer series are available. This is evident 

 from the fact that at Leroy, Colo., the 25-year normal precipitation is 

 17.19 inches (Table II) . Leroy is located about 30 miles northeast of 

 the Akron Field Station and is subject to similar climatic influences. 

 The average precipitation during the 11-year period, 1905 to 1915, is 

 19.51 inches at Leroy and 19.72 inches at the Akron Field Station. 



A droughty condition often prevails from about June 15 to August 

 31. The precipitation which falls during this period usually comes 

 in the form of hght showers. As the temperatures are high during 

 the summer months, this precipitation is rapidly lost by evaporation. 

 Table III, wliich gives the daily precipitation record at the Akron 

 Field Station for 1914, illustrates this point. This table shows that 

 from June 15 to October 8 there were only two rains of more than 

 0.25 inch. 



Table III. — Daily precij^tation recorded at the Ahron Field Station, Akron, Colo., 



for the year 1914. 



[Data(in inches) from the records of the Biophysical Laboratory of the Bureau of Plant Industry 



. T= 



trace.] 



1914 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dee. 



1 











0.25 



0.81 















2 









0.20 



0.02 













3 









, 





T. 

 T. 



' 0.17 



T. 







4 







T. 







.04 



T. 



1 



5- . 





0.02 



T. 



.12 



T. 



T. 











6 







.03 





0.07 

 T. 

 .08 

 .02 



T. 

 T. 

 .26 

 .14 





0.10 



7.. 











T. 



.40 



8 













.10 



9 



0.03 





T. 



.16 











.10 



10 









T. 





11 











.10 



.07 

 .11 

 .26 

 2 24 

 T. 













12 











T. 



"t." 













13 











.90 



0.01 



.06 









14 

















15 











.13 

 .03 

 T. 

 T. 







, 







16.... " 









.46 

 .27 

 T. 



T. 



.47 

 .23 

 T. 



""t." 



T. 



"'.'16" 



.25 

 .03 



.04 



T. 





0.10 





17 











18... 







T. 

 T. 











19 















20 











.6i 



T. 









21 











.06 

 .49 

 .96 





.20 



22 





.30 





.02 

 .87 

 T. 



T. 











23.... 





.02 

 .14 

 .22 

 .22 









24 







T. 





T. 



"tV" 



.17 

 .01 

 .08 

 T. 

 .65 







25. . . 













26 







.35 

 T. 

 T. 

 .49 

 1.07 















27... 









.05 

 T. 













28 







0.20 

 T. 

 T. 













29... 

















30 







"t.'" 



T. 



.02 

 T. 









31 - . 





























Total 



.03 



.32 



.20 



4.01 j 1.46 



3.54 



1.66 



1.05 



.23 



2.08 



.10 1 .90 



EVAPORATION. 



As a factor affecting crop production the seasonal evaporation 

 probably ranks next in importance to precipitation at the Akron Field 

 Station. The total evaporation from a free water surface for each 



