MANUBES FOE POTATOES. 263 



Bushels per acre. 



6i cwt. superphosphate ) 



2i " muriate of potash V321 



2i " sulphate of ammonia ) 



9 ( 6i cwt. superphosphate ( O q fi 



^}2* " sulphate of ammonia J 



3. No manure 252 



, ( 6i cwt. superphosphate ) g^ 



| 2i " muriate of potash J 



5. 2 cwt. sulphate of ammonia 238 



6. 15 tons farm-yd,rd manure 305 



u It is curious," said the Doctor, " that the plot with sulphate of 

 ammonia alone should produce less than the no-manure plot." 



" The sulphate of ammonia," said I, " may have injured the 

 seed, or it may have produced too luxuriant a growth of vine." 



Another series of experiments was made on another portion of 

 the same field in 1871. The "no-manure" plot produced 337 

 bushels per acre. Manures of various kinds were used, but the 

 largest yield, 351 bushels per acre, was from superphosphate and 

 sulphate of ammonia; fourteen tons barn-yard manure produce 

 340 bushels per acre; and Mr. Hunter remarks: "It is evident 

 that, when the produce of the unmanured soil reaches nine tons 

 [336 bushels] per acre, there is but little scope for manure of any 

 kind." 



" I do not see," said the Doctor, " that you have answered my 

 question, but I suppose that, with potatoes at fifty cents a bushel, 

 and wheat at $1.50 per bushel, artificial manures can be more 

 profitably used on potatoes than on wheat, and the same is prob- 

 ably true of oats, barley, corn, etc." 



I have long been of the opinion that artificial manures ccn be 

 applied to potatoes with more profit than to any other ordinary 

 farm-crop, for the simple reason that, in this country, potatoes, on 

 the average, command relatively high prices. 



For instance, if average land, without manure, will produce fif- 

 teen bushels of wheat per acre and 100 bushels of potatoes, and a 

 given quantity of manure costing, say $25, will double the crop, 

 we have, in the one case, an increase of : 



15 bushels of wheat at $1.50 $22.50 



15 cwt. of straw 3.50 



$26.00 



Cost of manure 25.00 



Profit from uing manure $1.00 



in the other : 



109 bushels of potatoes at 50 cents 50.00 



Cost of manure .. 25.00 



Profit from using manure $25.00 



