14 BULLETIN 878, IT. S. DEPARTMENT OF AGRICULTURE. 
the same period is stated, the latter being grown at all stations each 
year. The probable error of this difference also is given. In some 
cases the probable error of the difference is quite large, often indi- 
cating that the differences are not significant. 7 
RESULTS AT WILLISTON, N. DAK. 
The Willis ton Substation of the North Dakota Agricultural Experi- 
ment Station is located near Wilhston, N. Dak., on a fine sandy loam 
soil in the valley of the Missouri River at an altitude of 1,875 feet. 
The normal annual rainfall is 15.07 inches. The experiments at 
Wilhston have been conducted cooperatively by the North Dakota 
Agricultural Experiment Station and the Office of Cereal Investiga- 
tions. They were started in 1908 and discontinued at the close of 
the 1918 crop season. The yields of spring-wheat varieties are shown 
in Table III. 
The average acre yield of eight varieties grown during the 5-year 
period from 1908 to 1912, inclusive, shows the Kubanka durum wheat 
(C. I. No. 1440) to be the highest yielding variety at Williston, with 
an average yield of 24.5 bushels per acre. This yield is only slightly 
larger than that of the best variety of common wheat, Power Fife 
(C. I. No. 3697), which yielded only half a bushel less. Three strains 
of Bluestem wheat averaged 1.3, 2, and 3.1 bushels less than the 
Kubanka variety. 
The Marquis wheat was included in the experiments in 1913. Since 
that year it has increased rapidly as a commercial variety and since 
1916 has been the principal commercial variety grown in the Williston 
section. 
In the 6-year period from 1913 to 1918, inclusive, durum varieties 
have continued to outyield common varieties, including the Marquis 
wheat. In this period the Marquis has yielded at the rate of 30.2 
bushels per acre, while the Buford durum wheat, developed at the 
Wilhston Substation, produced the highest yield, averaging 34.4 
bushels. . The average difference of 4.3 bushels in favor of the Buford 
variety is significantly larger. The Kubanka (C. I. No. 1440) ranked 
second in yield, averaging 32.3 bushels. Power Fife also outyielded 
the Marquis in the 6-year period, with an average yield of 31.3 
bushels per acre. In shorter periods all other durum wheats grown, 
as well as four common varieties, outyielded the Marquis variety. 
Of the common wheats, however, none have yields significantly larger 
than that of the Marquis. In the two years, 1917 and 1918, the three 
rust-resistant durum wheats, Acme, Monad, and D-5, were among the 
highest yielding varieties. Of these, the Monad produced the highest 
average yield. 
7 The relatively large size of the probable error in some cases may prove misleading. It should not, how- 
ever, if it is borne in mind that the large size of this probable error is due partly to widely varying seasonal 
conditions in this section from year to year, causing the yields of all varieties to be very high some years 
and very low in other years. 
