The Barbados Sugar Cane Experiments. 351 



With the exception of the crop of 1887, ^" ^^^^ Y^^^ 

 manurings with superphosphate and potash salts have 

 given considerable increases in yield upon the un- 

 manured plots, showing the deficiency in the soil of 

 phosphoric anhydride and potash, and also that owing to 

 the favourable mechanical condition of the soil, sufficient 

 of the soil nitrogen underwent nitrification to supply 

 that necessary for the increased yield. In every case 

 the addition of 40 lbs. of nitrogen per acre produced 

 large increases in the yield, whilst the addition of another 

 40 lbs. still further increased it, although not to the 

 same extent. This is best seen in the following com- 

 parison of the average yields of the plots without 

 nitrogen, and of all the plots with 40 lbs. and with 80 lbs. 

 of nitrogen : — 



From these results we may safely conclude that, like 

 others of the gramineae the cane requires nitrogen ; that 

 manuring with nitrogen up to a certain amount will 

 yield increased crops, but that these increases rapidly 

 diminish in amount where manurings of over 40 

 lbs. of nitrogen per acre are applied. From my 

 experience, both of these experiments and of others, I 

 am of opinion that from 40 to 50 lbs. of nitrogen per 

 acre (equivalent to from 200 to 250 lbs. of sulphate of 

 ammonia) is, in the majority of cases, an ample manuring 



