PURCHASE AND USE OF FERTILIZERS 



335 



potash, and so on. Calculated in this way, the following table 

 gives the increase in yield of ear corn produced by phosphoric 

 acid, potash, and nitrogen respectively, from the Wooster Experi- 

 ment Field of the Ohio Experiment Station. 



These figures show the effect of phosphoric acid or potash or 

 nitrogen, alone, or added to the other forms of plant food. On 

 this particular soil phosphoric acid had the greatest effect, nitro- 

 gen next, and potash least. 



Other studies and applications of the experiments are made, 

 according to their character. 



Value of Increase. The profit in the use of different fertilizing 

 ingredients depends chiefly on the cost of the fertilizer and the 

 market value of the product. These two factors vary from year to 

 }ear, so that the prices used must always be given, and must be 

 carefully compared with present prices in studying the figures at 

 later periods of time. The profit can be calculated by subtract- 

 ing the cost of the fertilizer from the value of the increase in 

 crop. We can also calculate the profit or loss due to the use of 

 specific ingredients of the fertilizer as explained in the preceding 

 section. For example, the following results were secured from 

 seven years experiments with a rotation of corn, oats, wheat, and 

 hay on the Strongsville Farm of the Ohio Experiment Station. 1 

 1 Bulletin 184. 



