54 



Types of Cane Soil?. 



Moisture 





A. 



B. 



Organic matter and combined water 



10. OO 



b.Uo 



Silica and insoluble sillicates 



A Q AK 



GO. Qn 



bo .oy 



Alumina 



... 



io . 00 



« . ou 



Oxide 01 iron 



• • • ■•■ 





o aa 



Lime 





a on 



u . yy 



A AQ 



U . Uo 



Magnesia 





a oq 

 u . ^y 



A 



U . cO 



Potash 





0.11 



0.10 



Soda 



• • • • • • 



0.70 



0.09 



Phosphoric acid 



• • • • • • 



n i a 



u . 1U 



A AQ 

 U . Uo 



Sulphuric acid 





30 



'0.03 



Chlorine* 





51 



trace. 



Oxide of mangane 



se, carbonic acid, and loss 







in analysis 





0.42 



0.68 







100.00 



100.00 



Nitrogen (in organic matter) 



0.31 



0.05 



To persons accustomed to discuss analyses of soils nothing can be 

 easier than to see that in A we have everything that is requisite to 

 grow canes for a considerable numbers of years, whilst B is a soil fast 

 approaching to exhaustion. I will merely call attention here to the 

 greater amount of organic matter (humus), nitrogen, lime and phosphoric 

 acid in A, and to the important fact that in B the quantity of lime, 

 0.08, is far below that of the magnesia, 0.25. This I have ascertained 

 to be a very bad sign in cane soils, and it will probably be found to be 

 so in soils devoted to the cultivation of almost any other plant. 



It appears, indeed, from the results of a numerous series of analyses 

 carried on in my laboratory for some years past, that the degree of ex- 

 haustion which a cane soil has undergone can to a great extent be ascertained 

 by comparing the relative amounts of lime and magnesia yielded to 

 analysis. Here are four examples from the same estate in British 

 Guiana, from various portions of which the samples were taken : — 



Cultivated. 



, -A. , 



10 to 15 years. Upwards of 60 years. 

 Lime (per cent.) ... 0.44 64 Oil 0.40 

 Magnesia ... 0.32 0.50 0.36 0.51 



I might, perhaps, have found still more striking examples, but these 

 will suffice to show how the lime has disappeared (from the same soil) 

 by prolonged cultivation of the cane, whilst the magnesia has remained 

 pretty much as it was. 



In coffee soils from Ceylon I have found that the same thing occurs 

 also, but that the magnesia is more taken than with the cane. This is natu- 

 ral enough, since it forms an important ingredient among the mineral 

 matters of the seed of the coffee^plant, which seed it carried away from 

 the soil after each crop. However, even in coffee soils the magnesia 

 diminishes less rapidly by cultivation than the lime. It is quite pos- 

 sible in some cases to judge very approximately of the number of years 



* The quantity of chlorine ie unusually high, which is accounted for by the 

 proximity of a salt spring. Such springs are by no means uncommon in the island. 



