14 BULLETIN 253, U. S. DEPARTMENT OF AGRICULTURE. 
those months. Precipitation that comes after the weeds are killed 
by frost in the fall is as well stored by soil covered with dead weeds 
as by a turned furrow. Usually there is greater increase in moisture 
content in the spring-plowed plats during the winter than there is in 
the fall-plowed plats. This is due to the snow held by the stubble 
on the land which is to be spring plowed. Sometimes there is a very 
decided increase of the moisture in the spring-plowed land, which, 
with a normal summer precipitation, makes a great difference in 
yields. 
Moisture content in the spring is but one of the factors in the pro- 
duction of gram crops. Weeds growing with the crop may use enough 
water to decrease the grain yield materially. Fall plowing at the 
Akron station is especially favorable to weeds starting with the grain. 
Plowing in the spring thoroughly eliminates the weeds and, if done 
immediately before seeding, gives the grain crop the start of them. 
No other cultivation is so effective in destroying weeds as plowing. 
The ideal cultivation would prevent weed growth in the fall, leave 
the land hi such a condition that it would retain the maximum of 
snow in the winter, and retard the germination of weed seed until 
the crop starts in the spring. 
Early faff plowing effectively destroys weeds which use the early 
fall precipitation, but it does not leave the land in condition to retain 
the snow in the winter and it gives the weeds an opportunity to start 
before the crop. Spring plowing leaves the stubble to retain snow 
and reduces the number of weeds in the growing crop, but it does not 
prevent the loss of moisture by weed growth in the fall. 
In deciding the time to plow, the advantages and disadvantages 
of both spring plowing and fall plowing must be taken into considera- 
tion. Heavy rains in August indicate that fall plowing should be 
done, as the gain in moisture during the winter by stubble land prob- 
ably would not equal the loss by weeds in the fall. If only light rains 
occur, their loss probably would be more than offset by the greater 
quantity of snow held by the stubble durmg the winter and the reduc- 
tion of the weeds in the crop. Spring plowing would then be the 
better. The availability of labor in the fall will influence the amount 
of plowing done, but a greater effort should be made to do the plowing 
if there is heavy precipitation than if it is light. The only advantage 
in late fall plowing is that the amount of spring labor in preparing 
a seed bed is reduced. This advantage may be offset by a reduction 
in vield. 
CONCLUSIONS. 
(1) Early fall precipitation is used by weeds if land is left unculti- 
vated until spring. 
(2) Stubble prevents much of the winter snow from being blown 
off. The increase in soil moisture from this source usuallv more 
