178 PRINCIPLES OF FARM PRACTICE 



rotation with cultivated crops. For example, wheat follow- 

 ing corn which has been kept free from weeds will be 

 less injured by weeds than if following some uncultivated 

 crop. 



Other means of control that may be effective are heavy 

 fertilizing to induce a vigorous growth of farm plants so that 

 they may compete successfully with weeds; the use of animals 

 such as sheep and hogs for control, the latter being especially 

 useful in destroying bindweed; pasturing to reduce the growth 

 of tall weeds thus permitting the development of pasture 

 grasses; spraying with chemicals such as iron sulfate for 

 wild mustard and wild onion. 



It is also quite important that the seed of such crops as 

 clover, timothy and wheat be free from weed seeds. All 

 small seed used on the farm should be carefully examined 

 for weed seeds. The purchase of seed badly mixed with 

 weed seeds should be avoided. 



When seed is produced on the farm it should be screened, 

 several times if necessary, to remove the weed seeds. Many 

 of our most troublesome weeds have become established on 

 farms by the use of impure seed. For instance, the narrow 

 leaf plantain was seldom seen in fields a few years ago, but 

 becoming mixed with seed used on farms, it has grown to be 

 a common pest. 



All of our common weeds that are difficult to eradicate 

 should be so well known that they may easily be recognized 

 at any stage of their growth, and measures should be taken 

 to destroy them. It is especially important to keep them 

 from producing seed. 



In most states the desirability of controlling weeds is 

 recognized, and laws providing for their destruction on road- 

 sides and in uncultivated areas are enacted. Because of the 



