44 THE POTATO 



Unit Value. In order to find the unit value of the 

 different ingredients, divide the price per ton of the 

 fertilizer by the percentage, or number, of units of the 

 various valuable ingredients; this will give the cost per 

 unit. For example, if sulphate of ammonia be $66.00 

 per ton and contains 20 per cent, of nitrogen, then 

 66 -*- 20 = 3.30 per unit (see Table, p. 45). 



If the price per pound be desired, divide the price 

 per unit by 20, or the number of pounds in the unit; 

 thus, 3.30 -f- 20 = 16.5 cents per pound. 



For a fertilizer containing several ingredients, find 

 the lowest cost of each ingredient in a standard fertil- 

 izer as, nitrate of soda for nitrogen, muriate of potash 

 for potash, and acid phosphate for soluble phosphoric 

 acid and compare it with these. 



Purchasing Fertilizers. In purchasing fertilizers 

 it is advisable to write for quotations with guaranteed 

 analyses, ascertain, as indicated above, the cheapest 

 source of the valuable ingredients, and then purchase. 



The fertilizer containing a unit of plant-food at ttte 

 lowest cost is generally the one to buy. In figuring 

 the cost always include the freight, cost of hauling, 

 and handling; for instance, one ton of muriate of pot- 

 ash contains as much potash as four tons of kainit, 

 hence the potash as muriate of potash costs only one- 

 quarter as much for haulage and handling. The same 

 applies to high grade acid phosphate and low grade, 

 and unless the filler is of some particular value it is 

 wise to take the high grade or concentrated goods. 



Barn Manure. When not applied to the fields 

 as soon as made, it should be stored under cover and 

 the excrete from the various farm animals mixed, 



