326 



The Supplement to the Tropical Agriculturist 



THINNING-OUT HEVEA ESTATES. 



Opinions of Leading Authorities. 

 Quite a large number of estates are now com- 

 mencing tapping operations, and are therefore 

 in possession of trees four years old and up- 

 wards. A large proportion oi these areas were 

 planted in 1906, 1907 and 1908 in the respective 

 countries, and the problems now before planters 

 are of a varied character. In Ceylon, where, 

 owing to soil and elevation, the trees were 

 planted closer than jn Malaya and Sumatra, 

 some 60,000 acres were planted in 1906 and 

 50,000 acres in 1907 ; in fact those were the most 

 active years of rubber planting in that island. 

 Frequent distances at that period were 15 by 

 15 feet, or 20 by 10 feet ; these represent spac- 

 ings which would be properly described as close 

 planting in Malaya or Sumatra, but they are not 

 necessarily so on poor soil at an elevation of 

 1,000 feet and over above sea level. It is only 

 when tha trees, in Ceylon, reach their sixth or 

 seventh years that thinning out on a large scale 

 is forced upon planters ; elsewhere on estates 

 where the same distances have been adopted 

 thinning out has been commenced at a much 

 earlier age. 



In Malaya, as in Ceylon, large areas were 

 opened in 1906, 1907 and 1908. In 1906 the acre- 

 age was 99,000, in 1907 179,000, aud in 1908 

 241,000 acres, The distances adopted in those 

 years were a little wider than in Ceylon, popular 

 spacings then being 12 by 24, and 18 by 18 feet. 

 The same applies to Sumatra, except that many 

 of the estates there being under Liberian cofiee, 

 a wider distance, especially 20 by 20 feet, was 

 commonly adopted. 



Acreages Requiring Thinning-Out, 

 The broad fact remains that in Ceylon there 

 are about 100,000 acres, and in Malaya and Su- 

 matra a further 200,000 acres which are now 

 covered with trees, the branches and root sys- 

 tems of which are in frequent contact and al- 

 ready competing with one another for light and 

 soil. During the next year or so the problem of 

 thinning-out must be faced : otherwise there will 

 be a gradual reduction in yield of rubber consis- 

 tent with a slower rate of growth of the whole 

 plant and poorer bark renewal. 



The problem can be easily settled by those 

 parties who would simply reduce the number of 

 trees by half; but such a policy would, on many 

 estates, be unscientific and extremely wasteful. 

 Thinning-out must be taken in hand only after 

 the fullest consideration has been given to 

 distances, soil, climate, diseases, storms, past 



tapping, manuring and general methods of 

 cultivation. We will therefore study the methods 

 generally adopted and the importance of some of 

 these factors. 



Methods Now Adopted. 

 Let us first admit that thinning-out must be 

 done now or in the near future. Where thinning- 

 out is resorted to on young areas the plants can 

 be easily uprooted and destroyed, since the 

 quantity of rubber obtainable from the stumps 

 (or first eight feet) does not come into serious 

 consideration. This is by far the most prefer- 

 able course, and should in Malaya and Sumatra 

 be done when the trees are about three years, 

 and in Ceylon when they are about one year 

 older. At the ages indicated the remaining 

 trees can usually be expected to give a fair cover 

 to the ground and to rapidly throw their roots 

 into the soil set free during the thinning-out 

 process. 



On old estates the quantity of rubber obtain- 

 able from the stumps of trees being tuitmeJ-out 

 is quite considerable, and immediate uprooting 

 and destruction is therefore not generally 

 deemed advisable. 



On both young and old estates, and specially 

 the latter, there are two methods available. The 

 first is by cutting out all the trees in every al- 

 ternate row ; the second by removing only the 

 backward trees. The fi est method is the easiest, 

 most drastic, and most heart-breaking ; it 

 is based on the idea that in thinning-out half 

 the trees must be removed. If an estate were 

 closely planted and showed very even growth 

 it would be perfectly justifiable ; if the reverse 

 conditions prevailed, then it is quite conceivable 

 that complete good rows may be removed aud 

 bad ones retained, or that those lines of trees 

 removed might possess the best trees on the 

 estate, and those retained the worse on the 

 property. Where the estate is not eveD, or 

 where there is liability to death by various 

 causes, thinning-out by the secoDd method — 

 removal of backward trees— seems to be the 

 most sensible one to adopt. 



How Many Trees Per Acre ? 



But even this policy has its limits. It is quite 

 obvious that there is a minimum number of 

 trees per acre to be kept in view. And he is a 

 very wise man who can hit off that number. 

 Our view would be to ultimately thin-out down 

 to about eighty or ninety trees per acre ; this 

 would naturally be still further reduced from 

 year to year through diseases, storms, bad tap- 

 ping, etc. Diseases would be the most potent 

 factor in effecting reduction later on, the thin? 



