available phosphoric acid and potash contained in them, we Food ' or 

 have the following table : PUnts 



Composition of Different Grades of Fertilizers. 



IN 100 POUNDS OF FERTILIZER. 



In the fourth column, under the heading "pounds of 

 total plant-food," we give the sum of the Nitrogen, available 

 phosphoric acid and potash. We notice the following points 

 in connection with this table : 



1. The percentage of phosphoric acid does not vary 

 greatly in the different classes of fertilizers. 



2. The percentage of Nitrogen and of potash increases 

 in the higher grades. 



3. The total amount of plant- food in 100 pounds of fer- 

 tilizer increases in the higher grades, this increase being due 

 to increase of Nitrogen and potash. 



4. Representing the amount of Nitrogen in each grade 

 of fertilizer as i, we have the following proportions of avail- 

 able phosphoric acid and potash in the different grades : 



2*7 



Composition of Different Grades of Fertilizers. 



