Injuries from Weeds. 15 



able soil moisture. They are often more 

 capable of gathering food and moisture 

 from the soil than the useful crop, as their 

 root systems are usually more vigorous and 

 penetrate to a greater depth. When found 

 growing in a crop, therefore, they deprive 

 either that crop or the crops that come after 

 that one, of precisely that amount of water 

 and plant food which they consume during 

 their period of growth. The quantity of 

 plant food which weeds take from the crops 

 and the soil will be in proportion to the 

 numbers in which they are found. It should 

 not be forgotten that plant food externally 

 applied, often at much cost, as in the case 

 of commercial fertilizers will be utilized by 

 weeds quite as readily as the plant food nat- 

 urally" available in the soil itself. 

 (y^. Weeds injure useful plants by croivd- 

 ing and shading them. When useful plants 

 and weeds commence to grow at the same 

 time, the weeds will nearly always leave 

 the useful plants behind in the race. This 

 is owing to the superior power of gathering 

 plant food which nearly all varieties of 

 weeds possess. When present in a crop, 

 they usually grow more vigorously than the 

 crop itself, and as the latter is intended to 



