WEEDS AND THEIR CONTROL 213 



the practice is not an unmixed evil. Weeds also, under 

 some conditions, reduce the loss of nitrates from the 

 soil. 



On some of our heavy soils in older districts where 

 wheat lodges or ripens late, French weed or stinkweed 

 is frequently very prevalent. No farmer there will say 

 he prefers an infested to a clean farm, but many a 

 wheat grower because of the fact that this weed in a 

 fallow crop results in earlier maturity and in less 

 lodging of the grain, eases his conscience by considering 

 only its advantages. Such men are usually better phil- 

 osophers than farmers. Yet there are many people who 

 believe that the weed menace is a blessing in disguise 

 compelling as it does considerable tillage to keep it in 

 control. Whether one believes in this strange doctrine 

 or not the bald facts remain that farms do become 

 weedy, and that farmers must control weeds if they are 

 to make a living. 



170. Principles of Weed Control. Weeds spread by 

 means of seeds or by creeping root stalks or by both, but 

 in no other way. Weeds that spread by seeds can be 

 controlled by preventing seed formation. Weeds that 

 spread by creeping root stalks can be controlled by (1) 

 preventing seed formation, and (2) killing the plants 

 already established in the soil. But a man gets weeds 

 from outside his farm as well as from his own land. 

 Hence, if his plans are to be efficient, "he must also take 

 steps to prevent tile introduction of weedk to his farm 

 from elsewhere. 



The principles of weed control may then be stated 

 simply as follows : 



1st. Prevent the weeds from dteveloping secdk 

 2nd. Kill the perennial weeds. 



