CEREAL EXPERIMENTS ON THE CHEYENNE EXPERIMENT FARM. 5 
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 during 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. | Mar. | Apr. | May.| June.| July. fae Oct. | Nov. | Dec. SECee Annu- 
IU0 5 SSBAae 0.15 | 1.25 | 0.72 | 7.66 | 0.76 | 1.01 | 1.20 | 0.70 | 2.19 | 0.03 | 0.09 | 0.33 | 10.63 16. 09 
iO seaaes 13 | 1.10 | 1.54 | 2.97 | 2.47 | 1.93 | 1.34] .83 UB Ne Gelh | PCA ey 8.71 14.99 
NOO2E ee lo 21 DD locals Aon 2b lel Sokied. 49M econ osO2n|l a fO20 | 2d | leben L9 7.04 16. 50 
TOR qeeeae 20 | 1.76 | 1.00 | 2.10 | .46| 1.42] .79} 1.90 | 1.40]. .34 79 09 4.77 12. 25 
1904s oo 35 33 | .45 | 1.80 | 6.66 | 1.78 | 2.00} .87 83} .57 02) .06) 12.24 15. 72 
OR oe sane 84 69 | 1.27 | 6.45 | 4.04 | 1.90 | 2.97 | 1.93 | 1.06 | 1.40 11 02] 15.36 22. 68 
HOOG S20 -- : 21 21 | 2.27 | 3.10 | 1.30 | 2.42 | 1.89 | .49]} 1.86 | 2.33 | 1.42 15 8.73 17.65 
NOOMe ee 52 42 49| .49] 1.32] 2.78 | .34]| 3.50] .80 92} .08 59 55 7.94 12. 34 
HOOS Eee - 36 20 | .16 36 | 6.19 | 2.52 | 4.33 | 2.45 09 | 1.14 59 70} 13.40 19. 09 
SORE Eee 33 | 1.42 | 3.22 97 | 2.15 | 4.01 | 1.08 | 1.40 | 1.37 28 73 66 8.21 17. 62 
IQ SSedeee 29 31 | 1.45 | 1.14 | 2.34 76 | 1.32] .62] 1.80] 1.04 29 69 5. 56 12.05 
IQ Aes 49 56] .16] 1.93 33 | 1.64 | 1.21 | 1.35) 1.35 || ae 29 5. 11 10.85 
ROO tees Se =) 44 | 1.60 | 1.33 | 1.62 | 1.37} 1.17 | 1.82 | 1.44 | 3.91 | 2.59] .58 63 5.98 18. 50 
ORGS oa 59 7A | 338 | 1.35 12.22 101.51 102. 06/2209) 02. 23 | 1.43 | .37 | 2.00 7.14 16. 28 
Iie eee 10 23 72 |02. 54 01.46 |61.12 |61. 43 |52.03 }6 .32] 1.29] .26 16 6. 55 11. 66 
HOP OSs csi. 08 49 71 |54.90 |01. 78 |01. 83 |01.65 |62.53 |01.95 |01.81 | .03 | .56] 10.16 18. 32 
eee 2o2 | 275) | 1.12 | 2.6L | 2.43°) 1.68 | 1.88) 1.37 | 1.60.) 101 | -42 |) 264 8. 59 15. 78 
aX 1= : 
iene -| .84] 1.76 | 3.22 | 7.66 | 6.66 | 4.01 | 4.33 | 2.53 | 3.91 | 2.59 | 1.42 | 2.00} 15.36 22. 68 
ini- 
TANUITITES POS) | ee ZO ete LG: |e OOr| youl jj 1O4 |). (OMG 49 len O9N ies O3)/e. 02 4.77 10. 85 
a T=trace. 
+ Data obtained at the Cheyenne Experiment Farm by the Office of Biophysical Investigations of the 
Bureau of Plant Industry. 
EVAPORATION. 
Second to precipitation in 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 are the months of highest evaporation at Archer. The total 
evaporation for the four months varies considerably, ranging from 
20 inches in 1915 to 25.58 inches in 1914, 
_ The ratio of precipitation to evaporation during the growing season 
in 1913 to 1915, inclusive, is interesting and instructive. The data 
show that the ratio varies widely in the different years. The higher 
the precipitation, the nearer the ratio approaches equality and the 
higher the crop yields. Low evaporation is associated with high 
yields, provided the rainfall is normal. The evaporation during 
