I III II III I ■ III! 



FORAGE CROPS IN NORTHERN GREAT PLAINS. 



The mean temperature for the months from April to September 

 ranges from 40° F. in April to 69° in July, the average being 58°. 

 The average mean maximum for the same period is 72° and the mean 

 minimum 45°. The highest temperature recorded is 108° and the 

 lowest -57°. 



Table 4 gives the dates of the last and first killing frosts for the 

 years from 1910 to 1921, inclusive. The average date of the last 

 killing frost in spring for this period was May 17 and for the first 

 in fall September 19. The latest killing spring frost reported during 

 this period occurred on June 3 and the earliest in autumn on August 

 25. July is the only month that has been entirely frost free. The 

 average number of days between killing frosts was 125. The shortest 

 frost-free period reported during the years 1910 to 1922, inclusive, 

 was 83 days, and the longest 152 days, for the years 1910 to 1922. 

 This is 2 days more than the average for the years 1898 to 1909. 

 The prevailing wind is from the northwest, and the average seasonal 

 velocity for the years 1916 to 1922 was approximately 5^ miles per 

 hour. The highest average velocities occur in April and May. 



Moccasin, with an elevation of 4,300 feet, has the highest altitude 

 of any of the stations at which experiments were conducted in this 

 region. As shown in Table 5, the average annual precipitation for 

 the years 1898 to 1922 was 16.52 inches, and for the years 1912 to 

 1922, 16.3 inches. The average seasonal precipitation for the longer 

 period was 11.99, and for the shorter period 11.3 inches. The 

 maximum seasonal precipitation was 23.76 inches, in 1909, and the 

 minimum 9.9 inches, in 1919. The average monthly evaporation 

 for the years 1909 to 1922 is 33.4 inches. 5 The ratio of seasonal 

 precipitation to seasonal evaporation was 1 to 2.8. The mean 

 monthly temperature for the years 1909 to 1921 varies from 41° F. 

 in April to 64° in July, with an average of 55° for the months from 

 April, to September. The average mean maximum for the same 

 period is 68° and the average mean minimum 41° F. The highest 

 temperature recorded is 103° and the lowest —37°. 



Table 5. — Monthly, seasonal, and annual 'precipitation {in inches) in the vicinity 

 of Moccasin, Mont., from 1912 to 1922, with averages for certain years. 



[Data from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 





























Sea- 































sonal, 





Year. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Apr. 



to 

 Sept. 



Total. 































1912 



0.88 



0.60 



0.81 



1.43 



3.94 



0.64 



1.92 



1.27 



1.63 



1.68 



0.14 



0.06 



10.83 



15.00 



1913 



.89 



.09 



.20 



. 79 



2.64 



4.77 



1.12 



.51 



1.01 



1.63 



.93 



.38 



10.84 



14.96 



1914 



.47 



1.35 



1.12 



1.19 



2.91 



4.64 



.64 



.65 



1.11 



.74 



.64 



.21 



11.14 



15. 67 



1915 



.76 

 .74 



.08 

 1.22 



2.69 

 1.33 



1.43 



1.20 



2.12 

 2.25 



3.97 

 3.97 



3.54 

 2.03 



.92 

 1.29 



2.65 

 1.81 



.85 

 1.00 



1.01 

 .64 



.66 

 2.39 



14.63 

 12.55 



20.68 



1916 



19.87 



1917 



1.87 



1.30 



.85 



1.18 



2.79 



1.81 



.96 



.75 



2.91 



.62 



.09 



2.56 



10.40 



17.69 



1918 



2.34 



.62 



.57 



.44 



2.69 



1.55 



2.95 



1.48 



1.25 



1.09 



1.14 



.26 



10.36 



16. 38 



1919 



.13 



.71 



1.20 



.17 



.73 



1.08 



1.02 



.29 



1.48 



1.43 



.93 



.73 



4.77 



9.90 



1920 



.70 



.63 



.39 



5.37 



2.91 



3.97 



.89 



1.83 



.66 



.65 



.15 



.21 



15.63 



18.36 



1921 



.06 



T. 



.60 



.50 



3.31 



2.45 



3.87 



1.03 



1.69 



.03 



1.47 



.47 



12.85 



15.48 



1922 



.67 



.69 



.29 



2.12 



1.42 



4.43 



1.10 



.68 



.51 



.77 



1.19 



1.51 



10.26 



15.38 



Average: 

 1912 to 1922. 



.86 



.66 



.91 



1.44 



2.52 



3.03 



1.82 



.97 



1. 52 



.95 



.76 



.86 



11.30 



16.30 



All years, 































1898 to 































1922 



.71 



.48 



.82 



1.37 



2.75 



3.10 



1.92 



1.41 



1.44 



1.09 



.68 



.75 



11.99 



16.52 



5 From the records of the Biophysical Laboratory of the Bureau of Plant Industry. 



