14 BULLETIN 1293, U. S. DEPARTMENT OF AGRICULTURE 
manured rotation, No. 72, than in the unmanurecl rotation, No. 18; 
and following oats it averaged 373 pounds per acre more in the 
manured rotation, No. 71, than in the unmanured rotation, No. 19. 
RESULTS WITH WHEAT ON DISKED STUBBLE 
The practice of seeding wheat on unplowed stubble with or with- 
out previous disking or other tillage before seeding is very general 
in certain sections of the northern Great Plains. In Canada this 
system is most often used the second year after fallow, but it may 
follow a crop grown on either fall or spring pknving. In some cases 
several crops in succession may be stubbled in. 
Wheat was seeded on stubble only at Hettinger. Three plats, 
known as rotation No. 583, were cropped to wheat. On one of these 
each year the wheat was on fall plowing, on another it was on disked 
wheat stubble the second crop after plowing, and on the last it was 
on disked wheat stubble the third crop after plowing. This rotation 
was started in 1916, and six years' results are available. The fall- 
plowed plat exceeded the others in yield of grain only once, the first- 
year disked stubble yielded highest four times, and once the second- 
year stubble was best. The six-year average yield of the three 
treatments was: Fall plowed, 8 bushels of grain and 948 pounds of 
straw; first-year disked, 10.4 bushels of grain and 1,017 pounds of 
straw; and second-year disked, 9.6 bushels of grain and 1,037 pounds 
of straw. During the unfavorable seasons of 1919 and 1921, when all 
yields were very low, and in 1922, when the highest yields were ob- 
tained, the disked plats exceeded the fall-plowed one. 
Rotation No. 582 is a two-year rotation of wheat on fall plowing 
and wheat on disked wheat stubble. In this rotation the six-year 
average yield on the fall plowing exceeded that on disking by 1.1 
bushels, the yields being 4.5 and 3.4 bushels, respectively. There were 
two years of complete failure. For the same period the plat of con- 
tinuous wheat on fall plowing averaged 5.(y bushels per acre. 
The single plat known as rotation No. 581 grew wheat continuously 
without plowing for the six years from 1917 to 1922 and averaged 
4.5 bushels per acre. In 1922 it produced at the rate of 12.7 bushels 
of grain and 640 pounds of straw, compared with 13.5 bushels of 
grain and 1.890 pounds of straw on the spring-plowed plat in the 
continuous-cropping series. The latter plat averaged 5.6 bushels per 
acre for the six years from 1917 to 1922. Rotations Nos. 581 and 
582 are located some distance from rotation No. 583 and are not di- 
rectly comparable with it. 
The results of these experiments are perhaps more favorable to 
disking than those of more extensive trials would be, but they are in 
general accord with the results of similar experiments at other 
stations on the northern Great Plains. The yields of wheat on disked 
stubble the second year after fallow or plowing generally are de- 
creased somewhat but not sufficiently to condemn this system of 
cropping. The practice has the advantage of reduced cost, but the 
danger lies in the tendency to continuous cropping until the land 
becomes infested with weeds. 
RESULTS WITH GREEN MANURES 
Rotations containing rye, field peas, and sweet clover as green- 
manure crops were included at each of the stations. These crops 
