CHAPTER XVI 



WEEDS 



What weeds are. Nearly everyone knows that weeds are 

 plants which are not wanted. Someone has defined a weed 

 as a " plant out of place." Plants that are sometimes useful 

 may be regarded as weeds if they interfere with other plants 

 that are desired. Sweet clover is a good example of such 

 plants. Under certain circumstances it may be a valuable 

 crop for green manure, but at other times it may become a 

 pest. 



Losses due to weeds. " The direct loss in crops, the 

 damage to machinery and stock, and the decrease in value of 

 land due to weeds, amount, without question, to tens of 

 millions of dollars each year a loss sustained almost wholly 

 by the farmers of the nations." 



How weeds interfere with crop production. An ideal for 

 crop production would be to have all the necessary water, 

 plant food, and sunshine available for the plants being pro- 

 duced. The presence of other plants that make use of these 

 things tends to interfere with production by depriving the 

 cultivated plants of the amount needed for their best de- 

 velopment. For example, the amount of water taken up by 

 a vigorous weed amounts to as much or more than is needed 

 by a cultivated plant. Some recent experiments, designed 

 to determine accurately the effect of weeds on the production 

 of corn, showed a loss in the yield of as much as 38 bushels 

 per acre. This merely confirms what can be observed in 

 nearly every farming community. 



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