New York Agricultural Experiment Station. 393 



composition of fertilizers in different classes. 



If we compare our four dilTerent classes of complete fertilizers 

 in respect to the average amounts of nitrogen, available phos- 

 phoric acid and potash contained in them, we have the following 

 table : 



Composition of Different Grades of Fertilizers. 



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: 



(i) 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 fertilizer 

 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 fer- 

 tiUzer as i, we have the following proportions of available phos- 

 phoric acid and potash in the dififerent grades : 



Low-grade 



Medium- grade 



Medium high-grade 

 High- grade 



Nitrogen. 



Available 



phosphoric 



acid. 



7 



5-5 

 3-5 

 2 



Potash. 



2 

 2 

 2-5 



1.8 



