CHAPTER XL 

 EXTERMINATION OF WEEDS 



Among the most important considerations in connection 

 with the extermination of weeds are prevention of the 

 maturing of seed and the sowing of good seed only. In 

 the long run the more expensive clover seed is better 

 than the cheaper grade. Manure should be thoroughly 

 decomposed to prevent the scattering of weed seeds. I 

 .found that seeds of various weeds placed in manure that 

 underwent decomposition were destroyed. 



Cultivation. No other method is so good for the ex- 

 termination of weeds as cultivation by keeping the fields 

 clean. With ordinary cultivation the annual weeds are 

 readily destroyed. Where the field is very weedy it may 

 be necessary with perennial weeds to summer fallow, and 

 perhaps we may as well give the methods for destroying 

 a few of the perennial weeds. Take quack grass as an 

 illustration, which is the most injurious weed in the state 

 of Iowa, especially in the northern part of the state. 



The difficulty in exterminating weeds is due, in many 

 cases, to the prolonged vitality which many weed seeds 

 possess. Indian mallow, shoofly and other members of 

 the mallow family retain their vitality for years. The 

 seeds of many Leguminosae display the same character- 

 istic. Cases may be cited where fields which had been 

 in meadow for years upon being plowed soon abounded 

 in the greater ragweed, in the grain crop. Such weed 

 seeds may have been scattered by freshets, but the coats 

 of the involucre being very hard the seeds were thus able 

 to delay germinating. In the case of the cocklebur, one 

 "seed" germinates one year and the other the next. 

 When the seeds' coats are hard the seeds may retain 



87 



