CHAPTER V 

 FERTILIZERS 



CHEMICAL ELEMENTS NECESSARY FOR 

 GROWTH 



For the development of all plants certain 

 chemical elements are necessary. These are se- 

 cured from two sources, namely from the air and 

 from the soil. 



The essential constituents of plant-foods are 

 carbon, oxygen, hydrogen, nitrogen, sulphur, 

 phosphorus, potassium, calcium, magnesium, 

 and iron. Other elements are taken up by 

 plants but are not considered essential as plant 

 growth will occur without them. 



Of these food constituents, carbon and a part 

 of the oxygen are taken from the air. The car- 

 bon is taken up by the leaves in the form of car- 

 bon dioxide. 



The remainder of the elements are secured 

 from the soil. Of these, phosphorus, potassium 



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