432 



[December.! 1912. 



PROBLEMS OF HEVEA. 



The effect of Manure. 



The India- Rubber Journal of October 19, 1912, states it has been 

 argued that Hevea Brasiliensis is such a hardy tree and greedy feeder 

 that it will flourish eveu among rocks, and expenditure on manuring need 

 not therefore be considered. Hill-sides, flat plains, drains, swamps, vol- 

 canic soils, gravelly and stony terraces and other types of land appear to 

 provide sufficient nutrition for the rapid and continuous growth of Hevea 

 trees. 



A very instructive lesson can b > learnt from the experience of planters 

 dealing with other products in countries where rubber trees are also 

 grown. Probably the best example is furnished by the tea-planting 

 industry in India, Ceylon and Java. There are many estates which have 

 raised their output per acre, per annum, from 300 to over 600 lbs. by the 

 application of manures at regular intervals. It may, quite reasonably, 

 be argued that the results obtainable with a leaf product such as tea are 

 no guide to those which might accrue from the same treatment of rubber. 

 But it can be shown that manuring has a beneficial effect not only on leaf, 

 but on fruits and bark products. The effect of manures on fruit crops 

 —coconuts, cacao, coffee— is not always so obvious as in the case of tea, but 

 it is nosv common knowledge that judicious manuring does increase the 

 crop, and in many instances is absolutely necessary. 



Effect on Forest Vegetation. 



Unlike tea, coconuts, coffee and even cacao, rubber plants grow into 

 trees of enormous size and themselves form a dense forest. The soil under 

 forest vegetation of any type improves in mechanical and chemical 

 composition with age, owing to the protection which the trees afford 

 to the soil, to the actiou of the roots and the accumulation of leaf- 

 mould. The annual fall of leaf from Hevea rubber trees ultimately effects 

 an improvement in the soil in which the trees are being grown. This 

 is borne out by the analyses of the soils at Heneratgoda, the results piov- 

 ing that the organic matter, potash and nitrogen, are greater in the soil 

 which has been under rubber for twenty-nine years than that maintained 

 under pasture ; the lime and magnesia have decreased under the old rub- 

 ber, while the phosphoric acid is the same under both conditions. 



But these improvements do not justify any proprietor in declining 

 to assist nature and to supply still more food to the growing tapped trees. 



Relation of Latex to Bark. 



Where the soil is naturally very rich, it is granted that the turning 

 over of the soil by forking or chankolling will have as great an effect as 

 the actual application of manures on other soils. 



In tillage operations several points have to be borne in mind. In the 

 first case it must be remembered that the destruction of Hevea roots may 

 increase the amount of dead organic matter in contact with living roots, 

 and therefore considerably increase the risks from diseases in this and 

 other ways. It is quite clear that if root destruction is unavoidable the 

 roots must be cleanly cut and not torn ; the depth to which different soils 

 need tilling will determine whether that operation can be best done by 

 forking or chankolling. 



