4. Representing the amount of Nitrogen in each Food for 

 grade of fertilizer as 1, we have the following propor- Plants _ 

 tions of available phosphoric acid and potash in the 2 7S 

 different grades: 



Composition of Different Grades of Fertilizers. 



Cost of One Pound of Plant-Food in Different 

 Grades of Fertilizers. 



From these data, we readily see the truth of the 

 following statements: 



1. The cost of one pound of plant-food, whether 

 Nitrogen, phosphoric acid or potash, is greatest in 

 low-grade and least in high-grade fertilizers. One 

 purchaser of low-grade goods paid 36.8 cents per pound 

 for Nitrogen, while the highest price paid in high-grade 



