20 



Agricultural Chemistry. 



compounds alone were added, and to the others, nitrogen com- 

 pounds plus a small amount of plant ash. The plants in the pots 

 which received the ash grew to maturity, while those in the other 

 pots made only a feeble growth. 



Water cultures of buckwheat. This method of experimental culture, 

 which is known as water culture, has been of the greatest service 

 in determining which elements are essential for plant growth. 

 No. 1. Plant grown in normal solution. 



Plant grown in normal solution without potassium. 

 Plant grown in normal solution with sodium instead of 



potassium. 



Plant grown in normal solution without calcium. 

 Plant grown in normal solution without nitrogen. 



No. 2. 

 No. 3. 



No. 4. 

 No. 5. 



Non-essential elements. Besides the elements just named an 

 ash will generally contain sodium, silicon, chlorine, and frequent- 

 ly manganese, and perhaps minute traces of other elements. 

 These elements just named sometimes form a considerable portion 



