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Sri Lankan rubber industry is facing severe challenges due to the presence of relatively cheaper
synthetic rubber, poor quality lands, high labour cost and white root disease epidemic. Rubber
Research Institute of Sri Lanka (RRISL) has found intercropping of short rotation commercial
crops with rubber as a solution for these problems. Agarwood producing species of family
Thymalaeaceae are suitable crops for this reason as those can be rotated about three times in a
30 year lifespan of a rubber plantation. Those species form a highly valuable resin due to a
self-defense mechanism which can be induced artificially inside the stem. Therefore the present
study was conducted to identify the most suitable agarwood producing species to be
intercropped with rubber under different light conditions.
A field trial was established in RRISL premises of Dartonfield, Agalawatte for this reason.
Three agarwood producing species; Aquilaria crassna, A. subintegra and Gyrinops walla were
intercropped with rubber clone RRIC 121 planted in single and double row systems. The first
two have recently been introduced to Sri Lanka and G. walla is native to the country. Agarwood
species planted at 3m intervals in these intercropping systems were exposed to full sunlight
and 50% artificial shade. Stem diameter at 30 cm above the ground and total height were taken
as the growth measurements at monthly intervals for 15 months. Growth at the end of each
three month period was compared using one-way ANOVA using Minitab software.
According to the results, both diameter and height were not significantly different for all three
species when grown in 50% shade or under full sun. However, both diameter and height growth
of Gyrinops walla was significantly lower than A. crassna and A. subintegra when grown under
full sun and 50% shade in both single and double row systems of rubber at the 14th month.
Apart from the height growth at the 14th month under full sun of double row system, significant
differences were not observed for both diameter and height between A. crassna and A.
subintegra for all above treatments. Therefore it is evident that the growth of G. walla which
is native to Sri Lanka is lower even at the early stage than the introduced two agarwood
producing species.
