CEREAL EXPERIMENTS AT THE WILLISTOK SUBSTATION". 5 



growing season (April to July, inclusive) was 8.86 inches. The 

 maximum for any one growing season was 15.44 inches (in 1906) and 

 the minimum was 3.73 inches (in 1883). 



The rainfall is presented in graphic form in figure 1. The entire 

 height of the vertical columns represents the precipitation in inches 

 for the different years and the black lower portion shows the rain- 

 fall for the growing season (April to July, inclusive) for the same 

 years. The lower horizontal line represents the average seasonal 



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, SSASOA'AL 

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Fig. 1.— Diagram showing the precipitation at Williston, N. Dak.: Annual and average for the 40-year 

 period from 1875 to 1914, inclusive (shaded columns); seasonal (April to July) for the 36-year period 

 from 1879 to 1914, inclusive (solid black columns). 



rainfall for the growing season and the upper horizontal line the aver- 

 age annual precipitation for the 36 years included in Table I. 



EVAPORATION. 



Table II shows the monthly precipitation and monthly evapora- 

 tion during the growing season (April to July, inclusive) for the six 

 years from 1909 to 1914, inclusive. The evaporation as well as the 

 precipitation is an important controlling factor on the growth of 

 crops in the entire Great Plains area. The evaporation is determined 

 from a free water surface, the method being the one generally in use 

 where the Biophysical Laboratory of the Bureau of Plant Industry 

 has been cooperating. 1 



Table II. Monthty precipitation and evaporation at the Williston substation for the 

 growing season, 1909 to 1914, inclusive. 



[Data -in Inche ) from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 





Apr. 



May. 



.limn. 



July. 



Total. 



^ oar. 



Precipi- 

 tation. 



Evapo- 

 ration. 



Preclpi- Evapo- 

 tation. ration. 



Precipi- 

 tation. 



Evapo- 

 ration. 



Precipi- 



l.iil ion 



Evapo- 

 ration. 



Precipi- 

 tation. 



Evapo- 

 ration. 



1909 







Ml. 



u i,i 



1. 10 

 ..',2 



2. v.; 



. V, 



. I'l 



3.000 



:, 340 



:.. 791) 



1 B2 

 3.866 



2.84 

 1.30 

 :;.oo 

 i 59 

 1.06 

 1.31 



6. 166 



. m 



6.087 



1. 781 



5. 229 



6.603 



:i.72 

 1 . 66 

 l . 37 



1 . 69 



2. 16 

 7. 98 



.5.173 

 8.171 



7. 1 46 

 (i. 468 



7. c»7ii 



6. 2S9 



1.72 

 1.27 



1. in 

 3.00 



2. no 

 2.32 



6.018 



8. 99 1 



8.717 



5. '.ISO 



7. 164 

 7.1(12 



8.90 



r>. (12 



(J. 09 

 1 1 . 91 



6. 9. r , 

 12.00 



20. 057 

 28. 2(19 



I'd i 



27. 739 





21. 104 



I'd I. 



21. 491 





21.920 



A voraK" 



._ 



.86 





2 .::, 





3.08 



II. (IT, 1 



2. 1.', 



7.337 



8. 43 



21.030 



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