PRINCIPLES OF WEED CONTROL 



385 



Without waiting for either class of weeds to become a serious 

 pest on the farm we may control both classes by systematically 

 and regularly practicing this kind of rotation which requires the 

 change from rather permanent fields, such as grass lands; to the 

 cultivated fields, and then reseeding the cultivated fields with the 

 perennial crops. Examples of rotations for different sections are 

 suggested in Chapter XL 



Principles of Weed Control. The following brief memoranda 

 will help students and young farmers to keep in mind the various 

 methods of weed control, and the study of these principles will 

 serve as a sort of review of the points already given. 



(1) Never sow foul seed (Figs. 266 and 267). Have the seed 

 cleaned thoroughly before sowing it. Remember that numerous 



FIG. 266. FIG. 267 



FIG. 266. The wet thumb will pick up a layer of seeds from the sample. The reading glass 



or lens will help in detecting impurities. 

 FIG. 267. One of the quickest ways of roughly examining a seed-sample for impurities. 



weeds may be started directly by the farmer who sows clover, 

 grass or other farm seeds which are infested with weeds. Figures 

 268 and 269 will aid in identifying weed seeds found in samples. 



(2) If grains or other seeds are harvested on the farm itself, 

 they should be cleaned thoroughly by the use of the screen and 

 fanning mill before being used for seeding other fields. 



(3) Always cut annuals, biennials and perennials (all kinds of 

 weeds) before they ripen seed. Never allow seeds to mature if it 

 can be prevented. 



(4) Weeds are easier to kill during the stage that they are send- 

 ing up their flower stalks than at any earlier time in their growth, 



25 



