RUBBER 649 



Experiments by Tromp de Haas and others show that 

 under such conditions the yield in alternate day tapping 

 for a given period is less than that in daily tapping for 

 the same period. Doubling the number of cuts does not 

 compensate for halving the number of tappings. 



Again, experiments by Spring and others show that 

 doubling the area (horizontally) does not compensate 

 for halving the number of tappings. Trees tapped on 

 one-quarter daily yielded more than trees tapped in the 

 same way on opposite quarters (together) on alternate 

 days. 



Thus, whether the amount of bark removed is equalized 

 by doubling the number of cuts or by doubling the area 

 operated upon, alternate day tapping yields less in a given 

 time than daily tapping. 



The Pricker. 



The use of the pricker has now been definitely aban- 

 doned on, practically all estates in Ceylon. Experiments 

 by Simon :in Java have shown that, though the yield with 

 the pricker is at first greater than that with the knife, 

 it falls off more rapidly, and the yield at the end of six 

 months or a year is less. This is fully confirmed by the 

 results obtained at Peradeniya by using the old rotating 

 pricker. 



Experiments with the modern versions of this instrument 

 lead to the .same conclusion. 



An experiment with the most recent Northway pricker 

 at Peradeniya gave the following results : In two years 

 the original bark had been completely tapped up to a 

 height of 5 ft., the yield being 1,178 grammes per tree. In 

 the parallel tappings on the same plot by four different 

 excision methods, the consumption of bark in each case 

 was only three-eighths of the above, while the yield varied 

 from 1,690 to 2,180 grammes. These were for alternate 

 day tapping. In daily tapping by the Northway system the 

 original bark was completely tapped in seven and a half 

 months, the yield being 670 grammes per tree; but the 

 cuts did not heal properly, and it was then necessary to 

 rest the trees. 



