CEEEAL EXPERIMENTS ON THE CHEYENNE EXPEEIMENT FARM. 



The growing season, or the period during which spring cereals make 

 most of their growth, covers the four months from April to July, inclu- 

 sive. It is the rainfall durmg these four months that is of most vital 

 concern in crop growth. Most crop failures other than those caused 

 by factors of limited duration, such as hot wind, frost, or hail, are due 

 to the insufficiency or poor distribution of the moisture during these 

 months. According to the data recorded in Table I for the 16 

 years, 1900 to 1915, about 54 per cent of the annual precipitation 

 comes between April 1 and July 31, the period of most active crop 

 growth. 



Table I. — Monthly, seasonal {April to July), and annual precipitation at Cheyenne, 

 Wyo.,for the 16-year period, 1900 to 1915, inclusive. 



[Data (in inches) from the records of the United States Weather Bureau except as noted.] 



Year. 



Jan. 



Feb. 



Apr. 



May. 



July. 



Aug. 



Sept. 



Dec. 



Sea- 

 sonal. 



Annu- 

 al. 



1900 



1901 



1902 



1903 



1904 



1905 



1906 



1907 



1908 



1909 



1910 



1911 



1912 



1913 



1914 



1915 



Average 

 M a X 1 - 



mum. 

 Mi n 1- 



mum. 



0.15 

 .13 

 .21 

 .20 

 ..35 

 .84 

 .21 

 .42 

 .36 

 ..33 

 .29 

 .49 

 .44 

 .55 

 .10 



1.25 

 1.10 

 .55 

 1.76 

 .33 

 .69 

 .21 

 .49 

 .20 

 1.42 

 ..31 

 .56 

 1.60 

 .74 

 .23 

 .49 



0.72 



1.54 



2.11 



1.00 



.45 



1.27 



2.27 



.49 



.16 



3.22 



1.45 



.16 



1..33 



.33 



.72 



.71 



7.66 

 2.97 

 1.49 

 2.10 

 1.80 

 6.45 

 3.10 

 1.32 

 .36 

 .97 

 1.14 

 1.93 

 1.62 

 1.35 

 62.54 

 *4.90 



0.76 



2.47 



2.51 



.46 



6.66 



4.04 



1.30 



2.78 



6.19 



2.15 



2.34 



.33 



1.37 



2.22 



61.46 



61.78 



1.01 

 1.93 



1.55 



1.42 



1.78 



1.90 



2.42 



.34 



2.52 



4.01 



.76 



1.64 



1.17 



61.5! 



61.12 



61.83 



1.20 



1.34 



1.49 



.79 



2.00 



2.97 



1.89 



3.50 



4.33 



1.08 



1.32 



1.21 



1.82 



62.06 



61.43 



61.65 



0.70 

 .83 

 .53 



1.90 

 .87 



1.93 

 .49 

 .80 



2.45 



1.40 

 .62 



1.35 



1.44 

 62.09 

 62.03 

 62.53 



2.19 



.75 



3.52 



1.40 



.83 



1.06 



1.86 



92 



.09 



1.37 



1.80 



1.35 



3.91 



62.23 



6 .32 



61.95 



0.03 



.31 



.52 



.34 



.57 



1.40 



2.33 



.08 



1.14 



.28 



1.04 



.95 



2.59 



1.43 



1.29 



61.81 



0.09 

 oT 

 .23 

 .79 

 .02 

 .11 

 1.42 

 .59 

 .59 

 .73 

 .29 

 .59 

 .58 

 .37 

 .26 

 ' .03 



0.33 

 1.62 

 1.79 

 .09 

 .06 

 .02 

 .15 

 .55 

 .70 

 .66 

 .69 

 .29 

 .63 

 2.00 

 .16 

 6 .56 



10.63 

 8.71 

 7.04 

 4.77 



12.24 



15.36 

 8.73 

 7.94 



13.40 

 8.21 

 5.56 

 5.11 

 5.98 

 7.14 

 6.55 



10.16 



16.09 

 14.99 

 16.50 

 12.25 

 15.72 

 22. 68 

 17.65 

 12.34 

 19.09 

 17.62 

 12.05 

 10.85 

 18.50 

 16.28 

 11.66 

 18.32 



.75 

 1.76 

 .20 



1.12 



3.22 



.16 



2.61 



7.66 



.36 



2.43 

 6.66 



.33 



1.68 



4.01 



.34 



1.88 

 4.33 

 .79 



1.37 



2.53 



.49 



1.60 

 3.91 



1.01 



2.59 



.03 



.42 



1.42 



T 



.64 



2.00 



.02 



8.59 

 15. 36 



4.77 



15.78 

 22.68 

 10.85 



a T= trace. 



f> Data obtained at the Cheyenne Experiment Farm by the Office of Biophysical Investigations of the 

 Bureau of Plant Industry. 



EVAPORATION. 



Second to precipitation ui importance is evaporation, especially 

 that which occurs during the growing season. Table II shows the 

 monthly evaporation and precipitation at Archer for the four months 

 of this season in each of the three years 1913, 1914, and 1915. The 

 evaporation here recorded is from a free water surface, June and 

 July an; the months of highest evaporation at Archer. The total 

 evaporation for th<'. four months varies considerably, ranging from 

 20 inches in 1915 to 25.58 inches in 1914. 



The ratio of precipitation to evaporation dining tli<^ growing season 

 in 1913 to 1915, inclusive, is interesting and instructive. The data 

 show that the ratio vari(is widely in the difFi^rent years. The liigher 

 the precipitation, the nearer tlie ratio approaches ec^uality and the 

 higher the crop yields. Low (evaporation is associated with high 

 yields, |)r(A'id<'d tin; riiirifnU is iionnal. Tho evaporation during 



