TECTONA 745 



third quality ; on good soils the average height of the teak crop after three 

 years is 16 to 22 ft., and weeds are killed out. 



In Java the alang grass {Imperata arundinacea, Burmese thekke) is a great 

 scourge in young plantations. In order to prevent its ingress and to avoid 

 the expense of hoeing, Leucaena glauca is sown between the lines of teak ; 

 this plant keeps the soil clean, and is ultimately killed out by the teak. 



The frequency, intensity, and conduct of thinnings in teak plantations are 

 matters on which opinions differ to some extent, and the conduct of thinnings 

 must naturally vary in detail with local conditions. It is generally held that 

 thinnings should commence early, that is, at an age of about 10-12 years, or 

 even sooner, and should be carried out lightly but frequently up to an age 

 of about 25 to 30 years, after which plantations should be thinned somewhat 

 more heavily and at gradually increasing intervals of time. In fast-growdng 

 plantations it has been found advisable to thin at intervals of five years. In 

 Burma thinnings are ordinarily carried out at intervals of ten years, but it is 

 recognized that in the case of the younger plantations this interval is too long, 

 and has been adopted for the time being only because of the paucity of trained 

 staff. In Travancore, according to Bourdillon, thinnings commence in the 

 seventh year, and are repeated in the ninth, twelfth, sixteenth, and twentieth 

 years, and thereafter every fifth year. 



The scheme of thinnings for the Nilambur plantations has been recently 

 revised under Mr. R. Bourne's working plan. Generally speaking, in areas of 

 quahties I and II, thinnings under this scheme will commence at an age of 

 five years, and will be repeated at intervals of five years up to an age of fifteen 

 years, and thereafter at intervals of ten years up to an age of forty -five years, 

 after which no further thinnings will be carried out ; in areas of quality III 

 thinnings will commence at an age of ten years, and will be repeated at intervals 

 of five years up to an age of twenty-five years, and thereafter at intervals of 

 ten years up to an age of forty -five years, after which no further thinnings will 

 be carried out. The first thinning in each case is purely mechanical, every 

 alternate plant being removed from the lines in such a way as to leave the 

 remaining plants evenly spaced in squares, but each occupying double the 

 area it occupied previously. The last thinning is in the nature of an increment 

 felHng ; the number of stems left to form the final crop must vary with the 

 state of the crop, but the number per acre is roughly 35 on soils of quality I, 

 45-50 on soils of quality II, and 65-70 on soils of quality III. The yield table 

 given below (p. 763) under ' statistical ' shows the average number of stems 

 per acre left after thinning, and the intermediate yields at different ages in the 

 Nilambur plantations. 



Mixtures in plantations. The question of mixtures in teak plantations is 

 one which deserves further study. Teak is not a good soil-improver, and it 

 would often be advantageous silviculturally, where a natural underwood of 

 bamboos and woody species does not make its appearance, to introduce an 

 underwood artificially, choosing where possible a useful species whose cultiva- 

 tion would be remunerative. Various species have been tried in mixture 

 with teak, but where the companion species has been introduced along with 

 it, one of the two has almost invariably failed through being outgrown and 

 suppressed by the other. Where insect damage is to be guarded against. 



