140 TROPICAL AGRICULTURE CHAP. 



MANURING. On most of the sugar estates in the West 



Indies the canes have been planted on the same soil for very 



many years, and thus if the planters had not manured their 



Sugar cane lands, the soil would have become barren long ago, for the 



an exhaust- 

 ing crop. cane is a very exhausting crop, as it extracts large quantities 



Composition of inorganic matter from the land. Sugar itself is composed 

 of three organic elements, viz. : carbon, oxygen and hydro- 

 gen, all of which are obtained from the atmosphere and 

 water alone. But, in order to build up the sugar in its 

 tissues, the organs of the plant require quantities of inorganic 

 The quan- materials which must come from the soil. Careful analysis 

 of the cane, has shown that ripe sugar cane (Otaheite) contains 0*48 per 

 cent, of ash, which is about one part in nearly every two 

 hundred. A crop of 30 tons to the acre would remove, 

 therefore, nearly three hundredweights of the inorganic 

 constituents of the soil which exist in a soluble form ; and, 

 as the cane refuse or megass is used for fuel, and the tops 

 are used as fodder for cattle, nearly the whole of this inor- 

 Drain on the ganic matter is taken away from the soil absolutely. The 

 following table is calculated from an analysis of the ash of a 

 Analysis of ripe cane and its leaves by Dr. Phipson, and it shows at 

 cane. g glance what constituents are removed from the soil by the 

 canes, and what special kind of manure may be necessary to 

 keep up fertility : 



Potash 1800 



Soda 2.00 



Lime 10.00 



Magnesia 6.50 



Sulphuric Acid 8.00 



Phosphoric Acid .... 6.00 



Chlorine 4.50 



Silica 43.00 



Oxide of iron, manganese, &c. . 2.00 



100.00 



