230 THE RUBBER TREE BOOK 



badly-grown, misshapen trees, and all poor milkers. When 

 these have been felled and removed the roots must be extracted. 



After this has been done the soil should be well chankolled 

 over, at a distance of about 8 feet from each of the remaining 

 trees. This chankolling will have the effect of pruning the 

 roots, and will stimulate growth. Nearer the trees, where 

 there are larger roots, the ground should be well stirred up with 

 sharp-pointed sticks, so that it may be thoroughly aerated and 

 the beneficial bacteria stimulated to good works. 



On the well-known Pangkattan Estate, Bila, Sumatra, be- 

 longing to the Sumatra Para Rubber Company, Limited, the 

 effect of chankolling on the roots of rubber trees was very 

 marked. Some of the old trees rather closely planted were 

 beginning to suffer, and the yields of latex were falling off some- 

 what. Sixty acres were selected for experiment, and deep 

 chankolling was done about 8 feet from the trunks of the trees. 

 Nearer to the trunks of the trees the ground was well stirred up 

 with sharp-pointed sticks, so as to injure the main roots of the 

 trees as little as possible. The effect of this experiment was 

 very marked. For three months the yields of latex fell off 

 owing to the drastic treatment the trees had undergone by the 

 disturbance of the root system. Thereafter the trees picked up 

 wonderfully. The 60 acres selected for experiment gave an 

 increased return of latex over the figures for the previous year 

 of 250 Ibs. per month of first-latex quality (second-latex quality 

 and scrap not included) . This was a very marked improvement. 

 To very many planters the message might well be given Go 

 thou and do likewise ! 



