VALUE OF LEGUMINOUS COVER PLANTS 61 



The most practical means of vegetable manuring is 

 by cultivating various quick-growing plants and burying 

 them in the ground. When they decay acids are formed 

 which aid in the dissolution of some of the unavailable 

 plant-foods in the soil. Leguminous plants are most 

 largely used for this purpose in view of the property 

 which many of them possess of absorbing free nitrogen 

 from the atmosphere. The creeping, or low-growing 

 forms of Leguminosce are preferable to the shrubs and 

 tree forms, as the latter are often difficult to eradicate 

 without injuring the roots of the cocoa tree. Some of the 

 former varieties yield commercial products, such as the 

 ground-nut (Arachis hypogea) and the cow-pea (Vigna 

 catiang). When these are grown with the intention of 

 obtaining a crop before turning the plants into the soil, 

 their value as manurial agents is obviously depreciated. 

 In order to obtain seeds for future sowing it is advisable 

 to allow a certain number of the plants to produce seeds 

 before digging them in. 



The cultivation and burying of leguminous plants 

 cannot be expected to renovate completely exhausted 

 soils, as although these plants contribute more nitrogen 

 than they extract they only return the phosphoric acid 

 and potash which they obtained from the soil. 



In young cocoa plantations it is possible to bury the 

 plants grown for green manuring. A circular trench 

 should be dug around each tree, but sufficiently distant 

 from its roots to avoid injuring them. In this the 

 green plants should be placed, sprinkled with air- 

 slaked lime, gypsum, or wood ashes, and covered up 

 with soil. 



Lime assists the decomposition of the green material 

 and thus renders its constituents more quickly available as 

 food. Wood ashes are rich in lime, and frequently con- 

 tain from 6 to 9 per cent, of potash and about 2 per cent, 

 of phosphoric acid. Under old cocoa trees which densely 

 shade the ground green-manuring plants cannot be 

 profitably grown, but it is generally found that they will 

 thrive between the trees, provided that the latter have 

 not been too closely planted together. The advantages 

 accruing from protecting the soil in cocoa plantations 

 with a cover of leguminous plants has already been 

 dealt with. 



