DETERMINING THE MOST PROFITABLE FERTILIZER 371 



being the farmer's system should be much more simple 

 (Chapter XXI). 



Determining Profits From Fertilizers. The almost universal 

 method of interpreting fertilizer tests is to subtract the cost of 

 fertilizer from the increased value of the crop. If the value of 

 the increase is greater than the cost of the fertilizer, the fertilizer 

 is considered profitable. Authorities on farm management and 

 agricultural economics criticise this method because all the other 

 costs, such as interest, hauling and applying fertilizers, and har- 

 vesting, storing and marketing the increased crop, are disregarded. 3 

 All authorities would not count interest on " materials in process," 

 such as fertilizers and feeds. 



Since profits determine fertilizer practice, it is quite necessary 

 to give business interpretation of results of fertilizer tests. Net 

 value of the crop increase, therefore, should determine the conclu- 

 sions regarding profits from fertilizers. A check plot is necessary 

 to obtain the increased value of the crop. The value of the increase 

 minus the increased cost for fertilizer and additional labor, etc., 

 gives the net value of the increase. In all liberal fertilization it 

 is usually best to obtain the net value of the increases for the rota- 

 tion rather than for one year only. 



When the increase in yield gives only a small margin above 

 the mere fertilizer cost, the chances are the cost of application 

 and other increased costs would cancel this margin. 



An Example. On a soil deficient in available phosphorus, a 

 farmer applied 300 pounds of acid phosphate per acre for oats in a 

 three-year rotation of oats, clover and corn. A plot was left 

 unfertilized for a check. The increases per acre in three years 

 were seventeen bushels of oats, one-half ton of clover hay and ten 

 bushels of corn, the total valued at $22.50 (including straw and 

 stover). The cost of fertilizer, interest, application and all other 

 costs to harvest and care for the increase was calculated to approxi- 

 mate $9.00 for the three years. In this case $13.50 is the net 

 value of the increase per acre. These results clearly show that 

 acid phosphate was profitable. 



Determining the Most Profitable Fertilizer. Frequently on 

 lands in need of fertilizers, it becomes necessary to determine by 

 field tests which of two or more fertilizers, combinations of fertil- 

 izers or different amounts applied is the most profitable. The net 



3 Warren, Farm Management. 



