12 BULLETIN 33, U. S. DEPARTMENT OF AGRICULTURE. 
quotient is multiplied by the average yield of all check plats. The 
two methods are more clearly shown in the following equations: 
FIRST METHOD. SECOND METHOD. 
r=at+(b—-y). . L=A~-y Xb, or aby. 
Wherein, @=actual yield of variety. 
b=average yield of all check plats. 
“£=computed yield of variety. 
y=assumed yield of check. 
The check system as used at Dickinson has proved to be only 
fairly satisfactory. It affords a means of gaining a better idea of 
the relative yielding power of several varieties during certain seasons 
than would have been the case had no system designed for that pur- 
pose been used. In other seasons, however, the yields of the various 
check plats were influenced by so many uncontrollable factors (mois- 
ture, weeds, etc.) that to assume that any one of the other varieties 
would be affected by the same cause and to a like degree would be 
more of a theory than a determination. Usually the yields of the 
check plats were quite uniform; however, they sometimes varied as 
much as 50 to 100 per cent. A variety grown on a plat next to a 
high-yielding check plat will have a computed yield less than its 
actual yield. If next to a low-yielding check plat, the computed 
yield of the variety will exceed its actual yield. When the yield of 
a check plat is unusually high or low, the computed yield of varieties 
grown on adjacent plats are unusually and sometimes unreasonably 
low or high. Such instances cause one to accept with caution results 
based on computed yields alone. It is thought that actual yields of 
a variety for a period of several years, especially when the variety 
is shifted to several different places on the farm, are fairly depend- 
able. For these reasons and because computed yields are not available 
for all years, the conclusions in this bulletin are based principally 
on the actual yields. The computed yields for those years in which 
they were determined are given for the purpose of comparison. 
VARIETAL TESTS. 
The plat tests have included a large number of varieties and strains 
of cereals imported from various parts of the world. Many of these 
were introduced during the early years of the work and have since 
been discarded. Those varieties which appeared to be best adapted 
to the conditions of western North Dakota in regard to yield, growth 
habits, utility, etc.. have been continued in the trials, which have 
included 53 varieties and strains of spring wheat, 38 of spring oats, 
16 of spring barleys, and a number of varieties of winter wheat and 
rye, spring rye, and emmer. With some of these cereals the duration 
of the trials is too short to be conclusive, while with aka) some very 
satisfactory results have been obtained. 
