34 BULLETIN 1173, U. S. DEPARTMENT OF AGRICULTURE. 
In the depth-of-plowing experiments in which spring wheat was 
used for seven years and winter wheat for two years, the average yield 
of the subsurface-packed plats is 0.8 bushel more than the average 
yield of those not packed. The surface-packed plats also produced 
eee IDF 2 SWE SHO SUT SAE JHD SOF 
~~ 
o AVERAGE ot 
Ra ae Ba 
JET a 
5 | . 
NO FACKHING —es 
SYUB-SUAIACE FACHED  —=—---—---—-— 
SUATACE FACHED —-— 
Fia. 17.—Annual and average acre yields, in bushels, of winter wheat in varying numbers of years at Moro, 
= , J 
Oreg., and Lind, Wash., when grown after summer fallow for which the land had been plowed inearly - 
spring and either not packed or packed with a subsurface or surface packer after plowing. 
a slightly higher yield than those not packed, but in this case again 
the small increases in yield from the packed ground do not appear 
to be significant when considered in connection with the differences 
a es of the check plats used in this experiment, as reported in 
able 15. 
