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

Growth Comparison of Young Three Agarwood Producing Species Intercropped with Rubber under Different Light Conditions

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.Keywords: Gyrinops walla, Agarwood producing species, Intercropping, Rubbe

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

Effect of Time of Tapping on Latex Yield of Rubber (Hevea brasiliensis) in Kalutara and Moneragala Districts of Sri Lanka

Low productivity is one of the major concerns in rubber plantations and therefore, efforts should be made to exploit the maximum potential yield from a rubber tree sustainably. The exploitation of latex (tapping), which is the most important operation in rubber crop and plantations, is normally done in the morning (around 06:00-08:30) in traditional rubber growing areas in Wet and Intermediate Zones and around 05:00-07:30 in the nontraditional areas in Intermediate Zone. Some smallholders, planters and other people/groups believe or suggest that night or early morning tapping could increase the latex yield in rubber trees. Therefore, this study was aimed at exploring the effect of time of taping on the latex yield of H. brasiliensis. Rubber trees of clone RRIC 121 were used with a plot size of 15 trees and six treatments to represent times of tapping [03:00, 04:00, 05:00, 06:00 (control), 07:00 and 08:00)] at d2 frequency at Galewatta division of the Rubber Research Institute, Agalawatta, Kalutara District and 02:00, 03:00, 04:00, 05:00 (control), 06:00 and 07:00 at a smallholder field, Yudaganawa, Moneragala District for one year. Weather and latex volume data were recorded and total crop and g/t/t (gram/tree/tapping) were calculated/estimated. No significant differences were recorded for the mean total crop and g/t/t values for the trees tapped at different time intervals in both Kalutara and Moneragala districts. Models were fit to estimate the crops that could be obtained at different time durations using these data. Accordingly, a 0.04% increase in the total crop was estimated for trees tapped during 5:00-7:30 when compared to those tapped during 06:00-08:30 in the Kalutara District. Conversely, 1.6%, 3.3%, and 5.1% increase in yield were recorded in trees tapped during 04:00- 06:30, 03:00-05:30 and 02:00-04:30 respectively when compared to those tapped during 05:00-07:30. Therefore, night/early morning tapping may not be an effective or a practical strategy/solution to increase the productivity in rubber plantations in Kalutara District, while tapping during 02:00-04:00 in Moneragala District may contribute to an increase in latex crop upto around 5%. Large-scale assessments are required for further confirmation of these results. Keywords: Hevea brasiliensis, Latex, Morning, Rubber, Tappin

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

Efficacy of Exogenous Sodium Nitroprusside, Salicylic Acid and Moringa (Moringa oleifera) Leaf Extracts as Biostimulants on Growth and Physiological Attributes of Rubber (Hevea brasiliensis) under Sub-optimal Climatic Conditions

Stress phenomena that coincide, such as drought and heat, have been shown to affect the growth of rubber (Hevea brasiliensis) negatively under sub-optimal climatic conditions in nontraditional drier areas of Sri Lanka. Exogenous sodium nitroprusside (SNP), salicylic acid (SA), and moringa leaf extract (MLE) as bio-stimulants have been shown to improve the growth and physiology of crop plants under sub-optimal climatic conditions. Therefore, the present study aimed at exploring the effect of the above bio-stimulants on the growth and physiology of rubber under sub-optimal climatic conditions. Rubber plants of clone RRIC 121 cultivated in Hingurana, Ampara, Dry Zone (DZ) were spray treated with SNP at 100 and 200 µM, SA at 0.1 and 0.2 µM, and MLE at 5, 10% concentrations at monthly intervals for six months. Physiological parameters viz. chlorophyll content (cc), stomatal conductance (gs), and leaf water potential (Ψ) were recorded before and after three months from the commencement of treatments while growth measurements (girth and height) were recorded at three and ten months of treatments. Significantly higher girth values were recorded in plants treated with SNP, SA, and MLE at all concentrations compared to control and mock treatment after ten months from the commencement of treatments. Significantly higher chlorophyll values were recorded in plants treated with SNP at 100 µM (50.6±1.85), 200 µM (53.4±1.24), SA at 0.1 µM (49.5±1.49), MLE at 5% (50.1±1.98) and 10% (51.1±1.35) concentrations compared to control (41.9±1.15) and mock treatment (44.6±1.32) respectively after ten months from the commencement of treatments. Significantly higher leaf water potential values were recorded in plants treated with SNP, SA, and MLE at all concentrations compared to control and mock treatments after three months of the first treatment. Significantly lower stomatal conductance values were recorded in plants treated with SNP at 200 µM, SA at 0.1 and 0.2 µM, and MLE at 10% concentrations compared to control and mock treatments after three months from the first treatment. Improved growth and physiological attributes of rubber plants could be attributed to the beneficial effect of SNP, SA, and MLE as bio-stimulants. Therefore, exogenous application of the above bio-stimulants may be utilized for growth improvement in Hevea sp. under sub-optimal climatic conditions. Keywords: Bio-stimulants, Growth, Physiological parameters, Rubber, Sub-optimal climatic condition