18 FERTILIZERS 



will have to know in addition to the amount, the 

 market value and the source of the nitrogen, phos- 

 phoric acid and potash, before he can determine the 

 value of a ton of certain analysis. The source is 

 very important, because the most available forms 

 have the highest market value. Without this know- 

 ledge, a certain brand may sell for $40 a ton and 

 another worth only one-half its value ($20 per ton) 

 may sell more readily for $38. 



25. Each of the three essential plant foods has 

 its special part to do in the building of the plant. 

 One cannot do the work of the other. As an illus- 

 tration: Nitrogen in the absence of potash may 

 produce a luxuriant and rapid growth but it will 

 be weak, and broken down by the first wind ; add 

 potash and that same succulent, weak growth will 

 be matured and have strength enough to carry its 

 load of fruit. Potash alone will not produce the 

 growth, but will mature it. Both nitrogen and 

 potash have many other functions to perform. (69), 

 (71). 



Phosphoric acid, or phosphorus, must be present 

 in order that the plant may assimilate its nitrogen. 

 The process (osmosis) by which nutrients pass 

 through the plant from cell to cell is facilitated by 

 the presence of phosphoric acid. Phosphorus is nec- 

 essary for the seed's embryo development and for the 

 formation of chlorophyl (the green coloring matter 

 of plants). (70). 



Thus, while the essential plant foods each have 

 many independent functions to perform, they are 

 mutually dependent upon each other, and mutually 

 helpful in the building of the plant tissue. 



