See Mie os 
14 BULLETIN 1173, U. S. DEPARTMENT OF AGRICULTURE, 
a 
in the fall does not aid in better absorption of the autumn and winter 
precipitation. It more frequently deters moisture penetration by 
creating a mulch which holds the moisture near the surface and 
thereby hastens its escape by evaporation. This js especially true 
if the disking is done when the ground is dry. The standing stubble 
during the winter is no doubt a factor in increasing soil moisture, as 
IG6-3 LA = IGIS SHE FAT FT AIHE. AGIO AIZO ee 
I7OP?O, OAEG 
AVERAGE a -- Fee Je 
Oli pes 7 Ve 
SPAING DO/SAED ——————— 
NOT DISKED -------- 
Fia. 11.—Annual and average acre yields, in bushels, of winter wheat in varying numbers of years at Moro, 
Oreg., and Lind, Wash., when grown after summer fallow for which the ground had been plowed in early 
spring with the stubble disked or not disked in early spring before plowing. 
it helps to hold the snow where it falls and prevents drifting to a 
considerable extent. 
As is shown later, spring disking of the stubble generally proved 
beneficial if the plowing was done very late in the spring. Fall disk- 
ing, however, is not a satisfactory substitute for spring disking. 
because weeds and volunteer grain normally do not get started 
early enough in the autumn to be destroyed by fall disking. A good 
double disking in the spring ordinarily will kill all plant growth, 
which is the chief value of disking. 
