172 



Manuring of Potatoes. 



dung alone of about 30 cwts. of tubers per acre at an addi- 

 tional cost of 3 7s. In the Scotch and Lancashire experiments 

 it was also observed that potash exercised a powerful influence 

 in adding to the yield of the potato crop and in increasing 

 the size of the tubers. 



On the whole, therefore, the results of the experiments at 

 the three centres indicate that for the potato crop the best 

 artificial manure to be applied with dung is a complete 

 manure, i.e., one containing the three substances nitrogen, 

 phosphoric acid, and potash, and that the omission of any 

 one of these substances causes a reduction alike in the crop 

 and the profits. The necessity of including potash was clearly 

 demonstrated at all the centres. 



With respect to the question of the relative values of sulphate 

 of ammonia and nitrate of soda as a source of nitrogen for 

 the potato crop, the Yorkshire experiment furnished no marked 

 indications that one is superior to the other, nor did the 

 results of the trials in Scotland afford any conclusive evi- 

 dence that either of these articles possesses any material 

 advantage over the other. 



