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 sprmg is but one of the factors in the pro- 

 duction of grain 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 in 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 fall 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 during 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 yield. 



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 usually more 



