CONSTITUENTS OF COCOA TREES 



55 



measure returned to the soil by the annual leaf-fall ; if 

 the shells of cocoa fruits be also returned, the ingredients 

 actually taken from the soil are those used up in the 

 formation of roots, branches, and the beans. 



Harrison estimated that the annual production of 

 leaves, young shoots and fruits per acre on a cocoa 

 estate demands from the soil, amongst other ingredients, 

 138 Ib. nitrogen, 104 Ib. lime, 94 Ib. potash, 64 Ib. 

 phosphoric acid, and 31 Ib. magnesia. This estimate 

 includes leaves and fruit shells which are on most estates 

 re-incorporated in the soil. 



Cockrane estimated that in Ceylon, an acre of cocoa 

 trees, planted at the rate of 302 trees to the acre, and 

 yielding 1 Ib. of cured cocoa per tree per annum, would 

 require for the annual incremental growth of the trees 

 and the bean crop : 63' 4 Ib. lime, 59' 3 Ib. potash, 

 31' 5 Ib. nitrogen, 19 Ib. magnesia, and IT 7 Ib. phos- 

 phoric acid. 



On the basis of an annual average yield of 250 Ib. and 

 150 Ib. of cured cocoa per acre from Calabacillo and 

 Forastero varieties respectively, the under-mentioned 

 quantities of plant constituents are annually removed 

 from the soil by the beans in British Guiana (Proceedings 

 of the Agricultural Society British Guiana). 



Manurial Experiments. In order to ascertain the 

 plant constituents which the soil lacks, a different manure 

 should be applied to various parts of the plantation and 

 the effects watched. By this means the expense will be 

 saved of purchasing manures containing constituents 

 which are already abundant. For a fair comparison to 

 be drawn from the results obtained it is most essential 

 that the plots selected for experiment should be as like 

 as possible in every factor which would affect the experi- 



