and Magazine of the Ceylon Agricultural Society. — March, 1912, 



275 



such land when well drained, and especially if 

 liberally treated with lime, will bear trees 

 which show excellent growth and yielding capa- 

 city. In such cases the minor drains mast gene- 

 rally be placed b - tween every row of trees, and 

 special ditches dug to carry away the water. 

 It is generally sufficient if the water level can 

 be lowered 2 feet below the surface of the soil. 



The distance at which rubber trees should be 

 planted still gives rise to considerable discus- 

 sion in Ceylon, but the tondency is towards 

 wider and wider planting. At present the aver- 

 age number of trees to the acre in (Jeylon is 

 about 190, representing an average distance of 

 about 15 by 15 feet, but in good soil 20 by 20 is 

 now more generally recommended, and there are 

 authorities who consider even this too close. 

 There is something to be said also for the sug- 

 gestion to plant in clumps of three or four, allow- 

 ing the same number of trees to the acie. 



When the positions allotted for the plants 

 have been staked out, holes must be dug for 

 their reception. The larger the holes can be dug. 

 the better, as a good start is thus assured for the 

 plant, but funds will not often allow of a larger 

 size than a 2 foot cube. If the seeds have been 

 sown at the beginning of the wet season, they 

 may be planted out as soon as they have germi- 

 nated in the nursery; but if the sowing is late, 

 the plants may be allowed to grow until the next 

 wet season, and are then transplanted in the 

 form ofstumps. In planting the hole is filled 

 with good surface soil, to which it is usual to 

 add a little artificial manure. 



Cultivation and Manumng. 



As a general rule, all planted rubber is fenced, 

 in order to protect it from the attacks of ani- 

 mals. As soon as the rubber is planted the 

 Superintendent's chief duties are to see that any 

 vacaucies are supplied, and to keep the ground 

 clear of weeds. Weeding is a comparatively ex- 

 pensive operation, and many planters prefer to 

 reduce the expense by the cultivation of some 

 other product between the lines of rubber trees. 

 Theideal catch crop for this purpose still remains 

 to be discovered. Probably the most satisfactory 

 method is to grow some leguminous cover crop, 

 which may becut down at intervals and used as 

 nitrogenous mulch for the growing rubber trees. 

 By growing such a crop in lines across a steep 

 slope and by judicious mulching a good deal of 

 soil wash can be prevented, and a terrace forma- 

 tion induced, which is highly beneficial. The 

 same result can be obtained by laying the bran- 

 ches of dadaps trausversely across the slope. 

 Dadaps or similar trees are especially useful in 

 windy districts when the rubber is young, but 

 care mutt be taken to avoid overcrowding as the 

 rubber grows older. Of low-f;rowing nitro- 

 genous plauts, various species of Crotalaria, 

 Tephrosia, and Indigofera have been found ex- 

 ceedingly useful ; for an account of these re- 

 ference may be made to Circular No. 17 of Vol. 

 V., published in June, 1911. 



As regards the effect of forking or cultivating 

 the soil, opinions differ widely, and no reliable 

 data are available. But it is hardly to be ex- 

 pected that this expensive operation will lead to 

 much financial profit. On level land it is pro- 



bably better to conserve the surface mulch of 

 fallen leaves, and to imitate forest conditions as 

 closely as possible. 



Pjjuning. 



Except for the removal of dead branches, 

 pruning is not generally recommended in the 

 case ot well-grown rubber trees. Formerly a 

 process known as thumb-nail pruning was ad- 

 vocated, in which the terminal bud of the tree 

 was nipped off when a height of 12 to 15 feet 

 had been reached. The result of this treatment 

 was to cause a forking of the tree into two or 

 three main branches, and it was claimed that 

 the rate of increase in the girth of the main 

 trunk was accelerated. 



Tapping. 



A brief general account of the methods em- 

 ployed in collecting latex and in preparing from 

 it the pure dry rubber of export may here be 

 attempted. A start is made in the very early 

 morning, since the earlier the trees are tapped 

 the more freely does the latex flow. The rubber 

 is obtained from the trejs by one of many 

 methods of tapping, and different methods are 

 in vogue on different estates. Tapping methods 

 may ba divided into two main classes, those of 

 excision or paving and those of incision or 

 pricking, but the vast majority of estates both 

 in Ceylon and Malaya employ some modifica- 

 tion of the former, and we shall therefore begin 

 by confining our remarks to paring methods. 

 All these have the same object in view, namely, 

 the extraction of the largest possible amount of 

 good quality latex with the least possible injury 

 to the tree, the most obvious index of injury, at 

 least in the early stages of the process, being the 

 quantity of bark removed. Although other fac- 

 tors contribute to the result, it is generally 

 agreed that the amount of bark removed by par- 

 ing should be as small as is compatible with a 

 good flow of latex. 



In the majority of cases the process actually 

 employed is some modification of the one here 

 to be described. A vertical groove is first cut 

 in the outer bark of the tree extending to a 

 height of from 3 to 6 feet according to the cir- 

 cumference of the tree. From this at intervals 

 of about a foot oblique cuts are made sloping 

 upwards at an angle of 45 degrees, either on one 

 or both sides of the vertical channel, these 

 methods being described as halt and full herring 

 bone respectively. The slanting cuts are made 

 deep enough to tap the soft inner bark, but not 

 so deep as to injure the delicate cambial tissue 

 which adjoins the wood, and which provides for 

 the renewal of the cellular tissues from which 

 the latex is derived. 



A certain time must be allowed to escape be- 

 fore tapping can be recommenced on the renew- 

 ed bark, Iu (Jeylon it is generally customary 

 to allow three years for this process, but botani- 

 cal investigators are rapidly coming to the con- 

 clusion that this interval must be considerably 

 increased if the trees are t) continue in full 

 health and vigour. In addition, it has been re- 

 commended that the trees should be allowed a 

 series of intervals of complete rest. These 

 should be timed so as to coincide with the dryest 

 portion of the year. 



