Performance of three Agarwood Producing Species with Rubber in Different Intercropping Systems

Rubber growers in Sri Lanka face financial losses due to certain diseases affecting the latex yield and low price in international market. Use of a short rotation intercrop could be more effective to compensate such financial losses. Agarwood is an extremely valuable resin produced in Aquilaria and Gyrinops species of family Thymalaeaceae which is used in incense and perfume industries. Therefore it was decided to establish a field trial to investigate the growth performance of three agarwood producing species; Aquilaria crassna, A. subintegra and G. walla under two rubber planting systems, viz., single row with 12 m distance apart and double row with 18 m apart. Seeds were imported from Vietnam and Thailand for A. crassna and A. subintegra respectively and G. walla is native to Sri Lanka. The experiment site was established in May 2015, in 2 ha land of Dartonfield Estate of Rubber Research Institute, Agalawatte. One row of agarwood species were planted in the middle of single row system and three rows of those species were planted in double row system. Tree height and diameter measurements were collected from all (153) agarwood producing species at monthly intervals and leaf area and leaf chlorophyll content data were collected at three month intervals. Data were statistically analysed after four years of age by one-way ANOVA. According to the results, both Aquilaria species recorded significantly higher height (F=88.06, p=0.000) and diameter (F=3.92, p=0.000) than G. walla in both single and double row systems. Though diameter of two Aquilaria species were not significantly different some variations were observed for height. Leaf area of both Aquilaria species was significantly higher than that of G. walla (F=34.64, p=0.000) though there were no such differences observed for each species when grown in two intercropping systems. Chlorophyll content was significantly different only between A. crassna in both systems and G. walla in double row system (F=3.44, p=0.012). The analysis confirmed that both Aquilaria species are growing faster than G. walla though resin quality analysis is required for a proper conclusion.Keywords: Aquilaria, Gyrinops walla, Rubber, Intercropping, Agarwoo

Evaluation of Growth Performance of Agarwood Producing Species under Three Shade Settings in Different Rubber Intercropping Systems

Agarwood is a highly valuable resin mainly used as incense and perfume manufacturing and therefore a considerable foreign income can be obtained by the exports. Rubber, one of the main foreign income generating crops in Sri Lanka faces a severe threat due to low demand at the international market. Therefore growers are seeking for suitable short rotation species to intercrop with rubber. Along with that, the present study investigates the potential of intercropping three agarwood producing species; Aquilaria crassna, A. subintegra and Gyrinops walla of family Thymalaeaceae with RRIC 121 rubber clone under full sun, 50% and 30% shades. Those settings were made in two different planting systems, viz., double row (three agarwood lines between two rubber rows at 18 m distance) and single row (one agarwood line between two rubber row at 12 m distance) in 2 ha land of Rubber Research Institute, Agalawatte. G. walla is native to Sri Lanka and two Aquilaria species were introduced from Vietnam and Thailand respectively. Due to the fast growth rate, 50% and 30% shade settings were not applied for both Aquilaria species. Total tree height and stem diameter (above 30 cm of the ground) were collected from all (167) agarwood producing species in all two systems at monthly intervals. Data were statistically analysed after three years by one-way ANOVA using Minitab software. According to the results, both Aquilaria species grown in all systems recorded significant height and diameter growth than G. walla. There was no significant height or diameter growth difference between two Aquilaria species under full sun in both double row and single row systems. There was also no significant height or diameter growth difference between G. walla under all shades setting in all systems. Therefore the study revealed that the growth potential of G. walla is noticeably lower than selected Aquilaria species when intercropped with rubber.Keywords: Agarwood producing species, Gyrinops walla, Rubber, Intercropping systems, Shade setting

Prediction of the Early Growth of Plantation Grown G. walla

Certain tree species of Thymalaeaceae family produce highly fragrant, valuable resin called agarwood inside the stems, branches and roots due to a defence mechanism to protect internal tissue damage from invading microorganisms. Gyrinops walla is the only native tree species bearing the agarwood resin production ability which is growing in the low and mid elevations of wet climates of Sri Lanka. After some years of discovering the ability to produce agarwood resins in of G. walla, private sector investors planned to establish small and medium scale plantations using this species. However, information on G. walla growth rates under plantations conditions were not available, which are essential for the effective management. Therefore the present study aimed at constructing height and diameter prediction models for the early stages of G. walla plantations. For this purse, monthly measured height and diameter data of 40 plants of an even-aged G. walla plantation were used. Several non-linear and 2nd and 3rd order polynomial models were initially tested, keeping age as the single explanatory variable. Among them, the best performances were given by the 2nd order polynomial models for both height and diameter variables. Both models had R2over 99.0 and root mean square error and mean absolute difference less than 0.10, proving high accuracy. Fitted line plots also did not indicate deviations of the residuals. Though the models built in this study are recommended for predicting the early plantation growth of G. walla, future research should be conducted to validate them till the maturity of the trees. Keywords: G. walla, polynomial regression, growth modelling, plantation, height, diamete

Intercropping Agarwood Producing Species with Rubber for Sustaining Income

Sri Lankan rubber industry contributes to country’s economy in significant manner. Anyhow the natural rubber industry has now faced a threat due to the low price. As a solution, financially profitable other species can be intercropped with rubber to maintain sustainable income of the growers. Since agarwood has a very high demand and value in perfume and incense industry, it is worth to assess the feasibility of growing this crop with rubber. Therefore, the current study was conducted for the first time to test the potential of growing three agarwood producing species with young rubber under two intercropping systems, of which rubber is grown as a single row with 12 m and double row with 18 m spacing. The field trial was established using Aquilaria crassna, A. subintegra and the native species Gyrinops walla of family Thymalaeaceae in 2 ha land belongs Rubber Research Institute, Agalawatte in low country wet zone. A. crassna and A. subintegra seeds were imported from Vietnam and Thailand respectively while G. walla seeds were locally collected. All seeds were germinated in a nursery to raise seedlings. Then, one and three rows of agarwood species were planted at 3 m distance between rubber in single and double row systems, respectively.Tree height and stem diameter (30 cm above the ground) were measured at monthly intervals for all agarwood species (152 trees) while those of rubber (174 trees) were measured at six months and two months intervals respectively. Data collected for 4 years were analysed by one-way ANOVA and Student’s t-test. According to the results, G. walla recorded significantly lower height(F=168.58; p=0.000) and diameter (F=77.49; p=0.000) compared to both Aquilaria species in two selected intercropping systems. However, neither its height nor diameter was significantly different between two planting systems of rubber. Only A. subintegra in double row system was significantly taller than A. subintegra in single row and A. crassna in double row. Further diameter was notsignificantly different between Aquilaria species or planting system. However, the highest average tree height and stem diameter were recorded by A. subintegra in double row system and A. crassna in single row system respectively. Though diameter of rubber plants was not significantly different in two intercropping systems (t=-1.73; p=0.085), height in single row system was significantly taller (t=-3.71; p=0.000). The findings concluded that the growth performance of G. walla, the native species is comparatively lower than that of both Aquilaria species. Further, A. crassna and A. subintegra showed better height growth performances in single row and double row systems respectively. Keywords: Agarwood rubber intercropping, Aquilaria species, Gyrinops walla, Single row, Double row syste