CEEEAL EXPERIMENTS AT DICKINSON, N. DAK. 9 



Table IV shows that the highest average mean, maximum, and 

 minimum temperatures have been recorded in July, and that in this 

 month alone frost has not occurred. This table also shows that the 

 average mean temperature for the different seasons varied but little 

 from the 7-year average of 57° F. 



Table V gives the dates of the last spring and first fall frosts and 

 the number of days in the frost- free period during each year from 

 1907 to 1913, inclusive. The latest date on which frost has occurred 

 in spring during the 7 years was June 5, in 1910 and 1912 ; the earliest 

 frost in the fall during this period was on August 19, 1907. The 

 average frost- free period for the 7 years is 99 days. 



Table V. — Dates of the last killing frosts in the spring and the first killing 

 frosts in the fall at the Dickinson substation for the years 1907 to 1913, in- 

 clusive; also the temperatures recorded and the length of the frost-free period 

 for each year. 



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



Year. 



Last frost in spring. 



Date. 



June 4 

 May 21 

 May 17 

 June 5 

 May 27 

 June 5 

 May 21 



May 28 



Temper- 

 ature. 



F. 



First frost in fall. 



Date. 



Aug. 19 

 Aug. 21 

 Sept. 14 

 Sept. 8 

 Aug. 27 

 Sept. 21 

 Sept. 10 



Sept. 4 



Temper- 

 ature. 



Frost- 

 free 

 period. 



Bays. 



99 



1907 



1908 



1909 : 



1910: 



1911 



1912 : 



1913 



k Average 

 NATURE OF THE WORK. 



In all the varietal tests at Dickinson the primary object has been 

 to determine the relative yielding power of the different varieties 

 and to discover kinds better adapted than those ordinarily grown. 

 Efforts have also been made to improve the yield of the leading 

 varieties by selection and to find reasons for the existing variation 

 in yields between different groups of varieties of the same cereal. In 

 order to make these studies complete, it was necessary to divide the 

 work into plat and nursery experiments. The plat experiments -were 

 designed to conform as nearly as possible to the best farm prac- 

 tices in the northern Great Plains region. On these plats the crops 

 were studied on an extensive scale. In the nursery tests, which were 

 confined to short rows, the crops were studied intensively. The rows 

 were uniformly spaced and a weighed quantity of seed was planted 

 in each row. This method made possible the testing of a large num- 

 ber of varieties and offered a means of making a study of a consider- 

 able number of plants of each variety. 

 62800°— Bull. 33—14 2 



