THE CULTIVATION OF COCOA 169 



the humus of the soil is quickly destroyed by the 

 influence of the high temperature. 



Finally, it may be added that some kinds of manures 

 especially lime are also useful for converting com- 

 pounds, which are not available plant-food, into another 

 form which can be absorbed by the plants. 



A few of the most important manures for the 

 tropics may be mentioned here : 



A. Soil-improving (humus-affording) manures. 



1. Farmyard manure or pen manure (of cattle, horse, pig, 



sheep and goat ; contains about 3 to 5 per cent nitrogen, 

 2 per cent phosphorus, 4 to 6 per cent potassium, 2 to 6 

 per cent lime). 



2. Compost. ] Composition very variable, depending on the 



3. Mulch, j plants from which it is made. 



B. " Chemical " or " artificial " manures. 



a. Containing phosphorus and nitrogen : 



1. Bone-dust (contains about 20 to 24 per cent 



phosphoric acid and 4 per cent nitrogen). 



2. Peru guano (about 14 per cent phosphoric acid and 



7 per cent nitrogen). 



b. Containing nitrogen : 



1. Sulphate of ammonia (20 per cent nitrogen). 



2. Dried blood (12 per cent nitrogen). 



3. Chile saltpetre (in the tropics generally not so 



suitable as sulphate of ammonia, though much 

 used in temperate climates; contains 15 J per cent 

 nitrogen). 



c. Containing phosphorus : 



1. Basic slag, also called basic phosphate or Thomas 



phosphate (contains between 14 per cent and 20 

 per cent phosphoric acid and 50 per cent lime). 



2. Superphosphate (like Chile saltpetre, much used in 



temperate climates). 



d. Containing potash : 



1. Sulphate of potash (40 to 50 per cent potash). 



2. Kainit (about 14 per cent potash). 



e. Containing lime : 



1. Quicklime. 



2. Carbonate of lime. 



