242 SOILS 



phosphoric acid, and from 2 to 2.75 per cent, of potash 

 the commercial value being $30 per ton? 



Process : First, reduce the ammonia to nitrogen, since 

 it is the real element of plant food. Ammonia sounds 

 larger and hence is used in the fertilizer formulae. Re- 

 member that ammonia is not nitrogen. It is only four- 

 teen-seventeenths nitrogen, the other three-seventeenths 

 being hydrogen, which has no value whatever as a fer- 

 tilizer. 



So, to get the real amount of nitrogen in the ammonia 

 we shall have to divide the ammonia percentage by 1.214, 

 so as to get the percentage of nitrogen. 



Just do it this way: 1.95 -r- 1.214= 1.60: the nitrogen 

 percentage. We will then multiply each of the several 

 percentages (use only the smallest figures) by 20, so as 

 to obtain the number of pounds in a ton, and then multi- 

 ply this product by the value per pound, and we have the 

 value on the basis of a ton. 



The following shows the process : 



Nitrogen 1.60X20 = 32 Ibs. at 15 cents = $4.80 

 Phosphorus 7X20=140 Ibs. at 5 cents = 7.00 

 Potassium 2X20 = 40 Ibs. at 5.4 cents = 2.16 



Value of plant food in a ton $13.96 



So here is all there is to this estimate. When several 

 fertilizers are available, just make the calculation in this 

 way and you can then determine in which fertilizer you 

 get the largest quantity of plant food for the least money. 

 For the purpose of comparison, we will take another 

 fertilizer that sells for $29 per ton, just one dollar less : 

 its analysis is : nitrogen, 2 per cent., phosphoric acid, 

 9 per cent., potash, 2 per cent. 



With a first glance the average farmer might think the 

 first fertilizer, since it sells for a dollar a ton more, is 



