Gums, Resins, 



100 



[August, 1911. 



poor in phosphoric acid and lime— 5 cwt. 

 Thomas' » phosphate powder per acre 

 will meet the requirements ot the 

 rubber tree better than either of the 

 phosphatic dressings suggested above. 

 Furthermore, if the trees show a good 

 leaf growth, the nitrogenous dressing 

 may be decreased by one-third, whereas 

 if the leaf growth is weakly, better 

 results will be obtained by increasing 

 the nitrogen supply one-third. 



As to the manuring of young plant- 

 ations, the planter will be well advised 

 to make use of the nitrogen collecting 

 power of leguminous plants, which, 

 grown between the rows, and forked in 

 when they are in flower, are able to meet 

 the young rubber trees' requirements of 

 nitrogen. In order to enable the legu- 

 minous plants to develop vigorously, 

 and to accumulate an increased quan- 

 tity of nitrogen, it is, of course, neces- 

 sary to manure same with phosphoric 

 acid and potash, say 2 to 3 cwt. Thomas' 

 phosphate powder and \ to f cwt. muri- 

 ate of potash per acre. Such ''green 

 manuring" may be practised as long 

 as the growth of the leguminous plants 

 does not hinder the roots of the rubber 

 trees in their proper development. 



When, however, green manuring is 

 not adopted, the nitrogen has to be 

 applied by means of artificial manures. 

 Young trees should receive, during the 

 first year, a manuring with % oz. of 

 nitrate ot soda, % oz. oil cake, lj oz. 

 Thomas' phosphate powder, or \ oz. 

 concentrated superphosphate, and § oz. 

 muriate of potash per tree, these quan- 

 tities to be doubled from year to year 

 till the trees are fit for tapping, when 

 the full manuring suggested above may 

 be adopted annually. 



The artificial manures are to be 

 sprinkled around the trees. Until the 

 young trees reach their fifth or sixth 

 year, it is a better practice to manure 

 them singly, by distributing and fork- 

 ing in the manures around the stem at a 

 distance of from 1 to 1| ft. for each year 

 of the tree's growth. After the sixth 

 year the soil of a plantation is so 

 thoroughly permeated by the roots of 

 the trees that the artificial manures can 

 be distributed over the whole plantation. 



CASTILLOA ELASTICA: TAPPING 

 AND YIELDS. 



By Frank Evans, 

 Botanic Department, Trinidad, B.W.I. 



(From Tropical Life, Vol. VII., 

 May, 1911, No. 5.) 



There appears to be great diversity of 

 opinion, both as to the best method of 

 tapping, and the yield obtainable from 

 the Central American rubber tree (Cas- 

 tilloa elastica). 



Latest ^returns show very clearly that 

 estimates of yields made in former years 

 were far too high. 



Cross, in 1881, estimated the annual 

 yield of dry rubber at 121b. per tree; 

 another writer stated that the average 

 annual yield of trees in Nicaragua, when 

 tapped spirally, was 10 lb. per tree. 



In 1903 and 1904, trees in the Dominica 

 Botanic Gardens gave an average of 1 lb. 

 per tree. The tapping in 1903 was by 

 means of slits cut with an ordinary 

 knife, and in 1904 with a tool used in the 

 East tor tapping Hevea. The Dominica 

 experiments of 1905 conducted with a 

 view of ascertaining the best method of 

 tapping, favoured oblique lines cut 

 about ]8 in. apart on one-half of the 

 circumference of the tree ; this agrees 

 with the results ot Trinidad experiments. 



In 1908, when the writer carried out 

 trial tappings on plantations in the 

 Naparima district of Trinidad, good 

 results were obtained with oblique cuts 

 made with an Hevea tapping knife, also 

 with incisions made with an ordinary 

 2 in. chisel driven in with a mallet. 

 When using mallet and chisel, care 

 should be taken to drive in the chisel at 

 one level, as an upward or downward 

 cut is apt to split the bark. In 1910, 

 experiments with pricking instruments 

 were made at the Trinidad Experiment 

 Station; the idea being to puncture the 

 whole surface of the trunks to a height 

 of 8 to 10 ft. from the ground. Prelimin- 

 ary tests gave promising results, small 

 punctured areas giving yields amounting 

 to | to 2| lb. dry rubber per tree at one 

 tapping. The chief drawback to the 

 use of pricking instruments is the diffi- 

 culty of making clean cuts, the wounds 

 usually being rough-edged and heal 

 badly. Another objection is the amount 

 of labour required to continually force 

 in the prickers ; but this difficulty could 

 probably be overcome by the use of a 

 portable engine, worked by compressed 

 air, and connecting by tubing with the 

 tapping tool. The apparatus must be 

 light enough to be carried and guided 



