SOILS AND MANURES. 49 



manuring should not be necessary for many years providing 

 proper attention be given to soil cultivation. Where such lands 

 are chosen, a judicious rotation of catch-crops may be grown 

 which will not severely impoverish the soil, especially if the plants 

 be buried after harvest with dressings of basic slag or lime. The 

 planting of green crops for manurial purposes alone under these 

 conditions would be unnecessary waste of capital during the 

 early life of the plantation ; later the trees should have grown 

 sufficiently to shade the ground and thus prevent their being 

 cultivated. Where poor land, deficient in organic matter, has 

 been selected for rubber cultivation, green manures, and especi- 

 ally those belonging to the legume family, which are able to fix 

 atmospheric nitrogen by the aid of the bacteria associated with 

 the nodules on their roots, may be beneficially cultivated. 



These crops also improve the mechanical condition of the 

 soil by the action of their roots, and when they decompose, acids 

 are formed which assist in rendering additional plant foods avail- 

 able in a soluble form. The following are among some of the 

 most valuable kinds for rubber plantations : Vigna spp., " Cow- 

 Pea " ; Cajanus indicus, Spreng., " Pigeon Pea " ; Crotalaria spp. ; 

 and Arachis Jiypogcea, Linn., " Ground-nut." All these can be 

 readily grown from seed, of which from 20 to 30 Ibs. per acre is 

 required. Various species of leguminous trees, such as Albizsia 

 inoluccana, Erythrina spp. and Pithecolobiiim spp., can also be 

 employed with advantage, and if regularly pruned furnish a 

 valuable mulch, or better still ploughed into the ground with a 

 dressing of lime or basic slag. Mimosa pudica, the " Sensitive 

 Plant," has been recommended as a permanent green cover to 

 keep down weeds. It has been estimated that 150 to 200 Ibs. of 

 nitrogen per acre could be annually added to the soil by culti- 

 vating this plant, cutting it down, and turning it under the soil. 



The compact growing varieties of " Cow Peas " are specially 

 recommended. They grow rapidly on the poorest soils even 

 during the dry season, and their foliage contains a high percentage 

 of valuable manurial matters, i.e., .27 per cent, nitrogen, .10 per 

 cent, phosphoric acid, and .31 per cent, potassium oxide. It 

 should be distinctly understood that various other plants, such 

 as maize and sorghum, which are occasionally used as green 

 manures, only increase the organic matter in the soil, whereas 

 leguminous crops furnish in addition to this, supplies of 



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