18 BULLETIN 1203, U. S. DEPARTMENT OF AGRICULTURE 
the three-year rotations averaged 35.1 bushels and two on spring- 
plowed corn ground 35.3 bushels. Comparison of these yields with 
those in rotations containing sod shows an increase of about 1 
bushel of oats to the acre in the sod rotations, a quantity so small 
that it is of doubtful significance. It may be repeated here that 
at Dickinson oats on disked corn ground averaged 39.8 bushels, 
on green manure 12 bushels, and on fallow 15.5 bushels, yields all 
well above those on sod. 
"Wheat on disked corn ground in rotations Xos. 10 and 12 
averaged 20.6 and 18.1 bushels, or 19.1 bushels for the two. This 
is 0.3 bushel less than the average of all wheat at Dickinson on 
disked corn ground and 2.1 bushels less than wheat on fallow. 
Wheat on disked corn ground the third year after alfalfa in rota- 
tion Xo. 12 averaged 17.9 bushels. 
Flax on bromegrass sod in rotation Xo. 12 at Dickinson averaged 
7.9 bushels during the 16 years. A maximum of 30.7 bushels was 
obtained in 1915. There were three total failures, and in two years 
yields of less than 1 bushel per acre were obtained. Flax in this 
rotation at Hettinger averaged 5.3 bushels. There were two total 
failures, and a maximum yield of 10 bushels was obtained in 1912 
and in 1922. At Williston the average yield was 1.1 bushels with 
three complete failures and a maximum of 11.8 bushels in 1916. 
The yields were affected to only a very limited extent by wilt 
or other disease. At Dickinson in 1923 in the third round of the 
rotation only 2 per cent of the plants were killed by wilt. 
Weeds have been a much greater factor than disease in reducing 
the yields of flax. The worst of these has been Russianthistle. 
A sod rotation has not noticeably decreased infestation of this 
weed ; but, since the plats are small, the seed is scattered over them 
by the wind more than it would be in a larger area. Bromegrass 
has not been killed completely in wet years and by using the mois- 
ture has further reduced the yields of flax. In the earlier years the 
sod was broken in the spring shortly before seeding the flax. This 
practice has been changed to breaking some time after the brome- 
grass is harvested the previous summer, and much better results 
have followed. 
Oats at Hettinger on bromegrass sod averaged 27.1 bushels in 
rotation Xo. 11 and 21.8 bushels in rotation Xo. 12, or 26.1 bushels 
for the two. Following alfalfa in rotation Xo. 12 the average was 
28.1 bushels, or 2.3 bushels more than following the bromegrass. 
Oats following clover in rotation Xo. 11 averaged only 22.1 bushels. 
The clover failed so consistently that it can not be considered that 
the oats were grown on sod. On disked corn ground and fallow the 
averages were 32.2 and 35.1 bushels, respectively. 
The difference between the yields following alfalfa and following 
bromegrass may be owing to other factors than the differences in 
the sod crops. Corn silage in the alfalfa rotation yielded 832 
pounds less than in the bromegrass rotation, but wheat yielded 4.8 
bushels more. In a similar comparison at Dickinson wheat in the 
alfalfa rotation was exceeded by that in the bromegrass rotation 
by 1.5 bushels per acre. 
At Williston oats after bromegrass in rotations Xos. L0 and 12 
averaged 29.3 and 22.1 bushels, or 25.7 bushels for the two rota- 
tions." Oats at this station on spring-plowed grain stubble averaged 
