The Barbados Sugar Cane Experiments. 349 



and the average weight of canes per acre obtained in 

 the distrift: — 



Experiments with Nitrogen, 



In this portion of the experiments the objedl in view 

 was to ascertain : ist, the requirements of the canes for 

 nitrogen ; and 2nd, whether the canes were able to 

 make more complete use of nitrogen according to the 

 source from which it is derived. As the specific a£tion 

 of any manurial substance can only be developed for 

 its study upon either soil or plant when the other neces- 

 sary ingredients of plant food are present in relative 

 excess, in each year the plots used were manured 

 with such proportions of superphosphate of lime and 

 of sulphate of potash as our experience had shown to be 

 in excess of the requirements of the canes upon the 

 Dodds' soil. One plot was also yearly manured 

 with heavy dressings (20 tons per acre) of pen manure 

 and other plots left unmanured. Of the plots manured 

 with superphosphate and potash, one received nothing 

 in addition, the others nitrogen applied in different 

 forms and proportions. I propose here to consider 

 only the results obtained by the application of nitrogen 

 in quantities of 40 and 80 lbs. per acre in the forms 

 of sulphate of ammonia, nitrate of soda and of mix- 

 tures of dried blood and sulphate of ammonia. 

 The average yearly results are given in the follow- 

 ing table ; — 



XX 2 



