EXPERIMENTS OF THE BUREAU OF PLANT INDUSTRY. 33 



Table V shows the results of the experiments by States. As only 

 a small number of experiments have been conducted in some States, 

 it is probable that another set of tests would show considerable differ- 

 ence in results in many localities. It would not be advisable, there- 

 fore, to make practical suggestions for any particular locality based 

 on the indications of these results as a whole without first making 

 actual tests to see whether under local conditions these same prin- 

 ciples will govern. Where these results are found to hold good, how- 

 ever, two entirely new fields of research are opened up, and their 

 practical importance to the corn growers of America from a labor 

 and money saving standpoint is not to be gainsaid. 



If it be true that weeds make the cultivation of corn necessary the 

 problem immediately presents itself as to what farm-management 

 methods can be pursued to eliminate or reduce to a minimum the 

 weed pests of the farm. In this connection we have (1) the problem 

 of what may be termed persistent perennial weeds. Among this 

 group may be mentioned Johnson grass, quack-grass, Bermuda 

 grass, wild morning-glory, Canada thistle, wild onion, and horse 

 nettle. Publications already issued by the Department of Agri- 

 culture deal with the control of these pests. In the main these 

 weeds require special treatment to eradicate them. We have (2) 

 the biennial and annual weeds, which are troublesome largely 

 through their prolific seed habits. As a class these weeds should be 

 prevented from going to seed until all the seeds infesting the land 

 shall have germinated and the seedlings have been destroyed. 



Our present implements for cultivation are designed primarily to 

 produce a mulch and stir the ground. Weed killing is a secondary 

 function. It is possible that newly designed implements made 

 with special reference to weed control could accomplish this end 

 with greatly decreased cost. The weeder will probably be considered 

 of vastly more importance than heretofore when more data with 

 reference to its use are available. 



Another large field of investigation in connection with weed con- 

 trol is of much practical importance to the farmer. This field of 

 work might be outlined as a study of those systems of farming or 

 rotations which are especially calculated to lessen the weed pests 

 on the farm. It is a well-known fact that certain rotations of crops 

 bring us round to the tillage crop with the land practically free from 

 weed pests. One experiment is reported where a piece of sod land 

 very free from everything but clover and timothy was put to corn 

 and no cultivation given, as no weeds were present; a crop of 70 

 bushels per acre was produced. In some sections of the South, where 

 a 1-year rotation of corn and crimson clover is practiced, the weeds 

 are reduced to a minimum and many farmers cultivate corn on such 



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