198 FUNDAMENTALS OF AGRICULTURE. 



artichokes furnish excellent winter forage, and the dan- 

 ger of becoming pests is greatly reduced. Johnson 

 grass, the enemy of the cotton grower, has been widely 

 recommended by agricultural writers because of its 

 value for hay and pasture. As civilization advances 

 uses will be found for plants that are now considered 

 worthless, and as our knowledge and skill in plant 

 breeding increases many plants of little value at the 



A WEED-INFESTED FIELD. 



present time will be so improved that their cultivation 

 will yield a profit. 



Loss from Weeds. Weeds lower the yield of the 

 crop in which they grow in four ways. i. They util- 

 ize the available plant food in the soil that would 

 otherwise be used by the crop. 2. They use enormous 

 amounts of water in their growth, and often so ex- 

 haust the supply of moisture in the soil that the more 

 valuable plants are unable to withstand periods of 

 drought. 3. Sometimes the weeds get such a start 

 ahead of the other plants that they deprive them of 



