"Plants are an organized being, originating from a 

 germ and nourished solely by inorganic substance." 



PLANT FOOD 



The Assimilation of Salts. 



Plants require water, air, light and heat, cul- 

 tivation and fertile soil. Every crop removes 

 from the soil a certain amount of plant food. 

 Manure and nitrates must be added to restore 

 fertility. Plant food in the soil comes from 

 decayed vegetable matter, salts and minerals 

 found in the ground. 



The three constituents of the soil most drawn 

 upon by vegetables are potash, phosphoric acid 

 and nitrogen. Of these most soils contain lim- 

 ited amounts in available form and by contin- 

 uous cropping the soil becomes exhausted and 

 the plant suffers from hunger and does not 

 thrive. By adding fertilizer to the soil you 

 furnish the plant its necessary food. 



Humus. 

 Humus is the organic matter of dead leaves, 

 plants and animals that have lived and died 

 upon the land. Leaf mold and peat are ex- 

 amples. Humus is not essential to plant life. 

 Plants do not feed upon humus but upon its 

 component parts, potash, phosphoric acid and 

 nitrogen, which are formed from decomposed 



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