50 



whilst the so-called suckers and other young shoots trimmed annu Aly 



from the trees contain* 



Nitrogen ... .„ 84 lbs. 



Phosphoric anhydride ... 49 " 



Potash ... ... 42 « 



Lime ... ... 66 " 



Magnesia ... ... 20 " 



These together with the leaves which he states contain — J 



Nitrogen ... ... 39 lbs. 



Phosphoric anhydride ... 7-5 " 



Potash ... ... 30 « 



Lime ... ... 32 *' 



Magnesia ... ... 10 " 



are practically in all cases yearly returned to the soil. 



The fruit, of which the husks may or may not be returned to the soil' 

 according as to whether the pods are or are not broken on the field, are 

 estimated to remove as follows : 



If whole fruit re- If the pods are 

 moved from the broken and left in 



field. the field. 



Nitrogen ... ... 15*5 8*7 lbs. 



Phosphoric anhydride ... 7*9 4*6 " 



Potash ... ... 22-1 3-7 " 



Lime ... ... 6 5 1-4 « 



Magnesia ... ... 2-0 1-0 " 



From these figures it appears that the cocoa tree whilst stor- 

 ing up in the plant itself relatively large proportions of the important 

 elements of plant food present in the soil, requires for the yearly pro- 

 duction of young shoots, leaves and fruit not less than 138 lbs. of nitro- 

 gen, 64 lbs of phosphoric anhydride, 94lbs. of potash, 1 04 lbs. of lime 

 and 31 lbs. of magnesia. Under careful conditions of agricultural prac- 

 tice, howev er, of this great annual drain upon the soil but 8*7 lbs of nitro- 

 gen, 4"5 lbs. of phosphoric anhydride, 3*7 lbs potash, 1*4 lbs of lime and 

 1 lb. of magnesia are necessarily removed from it, the remainder becom- 

 ing more or less available again for plant food by the decomposition of 

 the fallen leaves, prunings and husks upon the land. Of the, in round 

 numbers, 130 lbs of nitrogen returned to the soil a considerable propor- 

 tion, possibly 20 to 30 per cent, may be lost during the decomposition 

 of the vegetable matter, but where the trees are shaded by the nitrogen 

 collecting Bois Immortel or OroEoque tree (Erythrina velutina and K. 

 umbrosa which are used on the islands, or E. glauca which is used iu 

 Guiana) doubtless much of the amount thus lost is recouped to the soil. 



Hence, from these considerations, we are led to the conclusion that a 

 good cocoa soil should be one capable of yielding to the tree in the course 

 of years a somewhat high proportion of the important constituents of 

 plant food without exhaustion, and also capable of rapidly rendering 

 again available the large quantities of manurial matter returned to it in 

 the forms of prunings, leaves fallen and broken pods. It must in addi- 

 tion be one in which the course of nitrification readily take place : in 

 other words, a fairly rich friable and well drained soil. 



♦This estimate appears to us from our somewhat limited experience as excessive. 



