14 BULLETIN 10%, U. S. DEPARTMENT OF AGRICULTURE. 
not ready to plow under until in September. The average date for | 
plowing under field peas has been June 20. This is three weeks later 
than the plowing under of rye, but the fallow period is more com- 
parable than it could be with cowpeas. Rye, being ready to plow ~ 
under three weeks earlier than peas, has a fallow period that much ~ 
longer, and there is that element of difference in addition to the dif- — 
ference in the character of the crop. Itis ‘a difference, however, that 
is inherent in the nature of the crops and can not well be avoided. 
The average yield of wheat in rotation No. 92 is 14.9 bushels and in 
rotation No. 56, 15.5 bushels. Again, in this pair the higher yield is 
from the rotation having kafir instead of corn two years before the 
wheat. The difference, however, is too small to be significant. 
Rotation No. 92 has no record for 1908, as winter wheat was omitted 
from it by error. It was seeded to spring wheat, but the yield can 
not be used in comparisons with winter wheat. The average yield 
of the two plats following peas used as green manure is 15.2 bushels 
per acre. This is 0.2 bushel more than the average of the two 
plats following rye used as green manure. Lach of the plats on peas 
has yielded more than one of the plats on rye, but less than the other. 
The evidence presented by the wheat crop alone is not sufficient to 
distinguish any difference between a legume and a cereal as green 
manure. Any minor difference there may be is of little significance 
in comparison with the fact that neither one has produced yields as 
high as the less expensive bare fallow and only barely or not quite 
equal to those obtained from the best methods of preparation follow- 
ing a wheat crop. With the longer fallow period enjoyed by the 
ereen-manure plats it seems that their yield should exceed that 
following a wheat crop and more nearly approach that of the still 
longer period of the bare fallow. This is their general behavior at 
most dry-land stations. 
Two other 4-year retations contain green manure. Rotations 
No. 53 and No. 54 are similar to No. 51 and No. 92, with the positions 
of the corn and green manures exchanged. In these two the barley 
is on green manure and the wheat on disked corn ground. Rotation 
No. 53 is rye for green manure, barley, corn, and winter wheat, and 
rotation No. 54 is peas for green manure, barley, corn, and winter 
wheat. The average yield of wheat in rotation No. 53 is 14 bushels 
and in No. 54, 16.2 bushels per acre. This apparently shows a clear 
advantage of the legume over the cereal as a green manure that was 
not shown in the rotations where wheat immediately followed the 
green manure. The wheat in one of these rotations yields less and in 
the other more than wheat following wheat on early-fall plowing, but 
less in each than wheat following wheat on subsoiling or early listing. 
They of course yield markedly heavier than wheat following wheat 
on late-fall plowing. 
