of potato fertilizers are given. The percentages of plant-food elements in such 

 fertilizers made by reliable firms varied as follows : Nitrogen, .93% to 5.03%; 

 phosphoric acid (available), 4.447o to 9.57%; phosphoric acid (total), 5.31 to 

 12.81%; potash, 2.01% to 11.20%. 



FACTORY MIXED FERTILIZERS. 



If, then, a " potato special " is to be used it is essential to have a clear idea 

 about what composition is desirable. It is not enough to call simply for a 

 potato fertilizer. 



As a result of experiments and observation I am inclined to recommend : 



A. When fertilizers only are to be used. 



1. On clover sod or soils rich in humus and relatively fertile : 



Per cent. 

 Nitrogen, 2.5 — 3. 



Phosphoric acid, 8 — 10. 



Potash (in form of sulfate), 8 — 10. 



2. On lighter and poorer soils : 



Nitrogen, 3.5— 4.5. 



Phosphoric acid, 6 — 8. 



Potash, 8 —10. 



B. For use in connection with manure. 



1. On clover sod or soils rich in humus: 



Nitrogen (mostly in soluble forms) , 



Phosphoric acid, 



Potash, 



2. On lighter and poorer soils : 



Nitrogen (mostly in soluble forms). 



Phosphoric acid, 



Potash, 



Of such fertilizers, when used alone, 1500 to 2000 pounds per acre; those to 

 be used with manure, 600 to 1000 pounds per acre. 



HOME MIXTURES. 



The judicious selection and purchase of unmixed materials usually makes it 

 possible to obtain needed elements of fertility at lower cost than in " potato 

 specials," but this is in part because the trade in unmixed materials is almost 

 exclusively on the basis of cash payments, while the trade in mixed fertilizers 

 is to a considerable extent on a credit basis — crop time. It is the part of 

 wisdom before deciding on the purchase of materials to obtain quotations for 

 cash on a " potato special " of the desired composition and to compare these 

 with quotations on materials which will give a fertilizer of the same general 

 composition, plus the necessary charge for the labor of mixing. It is, moreover, 

 no doubt in some cases necessary to make some allowance on account of shrink- 

 age in unmixed materials caused by torn or overthin bags ; but it is possible 

 that there may be some shrinkage also on the ' special " mixed goods from the 

 same causes. The labor of mixing is neither diflficult nor expensive. 



