16 



BULLETi:sr 1039, u. s. depaetme:k-t of ageiculttjee. 



amounts and distribution of the seasonal precipitation. The yields of 

 the durum wheats were considerably reduced in 1910, on account of 

 hot winds at flowering time which prevented fertilization. In 1911 

 the wheat sown in the spring did not emerge until August. The 

 failure in 1912 was caused by a deficient supply of soil moisture in 

 the spring, together with the low precipitation during May and June. 

 In 1916 the wheat was badly injured by rust. 



The durum varieties have outyielded the common varieties in 

 nearly all seasons. This was due only in part to the greater resistance 

 of durum wheat to rust and drought, for the durum varieties have 

 given the highest yields in the most favorable seasons. The Kubanka 

 variety, C. I. No. 1516, has the highest average yield during the en- 



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26 



•30 



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 MaSABU. 



Fig. 5. — Diagram showing the average yields, in bushels per acre, of seven varieties 

 of spring wheat on dry land at the Belle Fourche Experiment Farm during the 7-yeai' 

 period from 1913 to 1910, inclusive. 



tire 12 years and also during the T-5^ear period, 1913 to 1919, inclu- 

 sive. This variety appears to be slightly more productive than the 

 Kubanka strain, C. I. Xo. 1440, and is slightly different in appearance. 

 A head of Kubanka wheat is shown in figure 4. 



Several other durum wheat varieties yielded about as much as or 

 even more than Kubanka during the three years 1917, 1918, and 1919. 

 These small differences probably are not significant. 



Marquis is the highest yielding variety of common wheat. During 

 the period from 1913 to 1919, inclusive, it outyielded all other com- 

 mon-wheat varieties. A head of Marquis wheat is shown in figure 4. 

 Manchuria, the second highest yielding common wheat, is a soft 

 wheat of low milling and baking value. The Power, Haynes, and 

 Preston varieties show average yields since 1913 considerably below 

 that of Marquis. The yields of the leading varieties grown since 

 1913 are shown graphically in figure 5, 



