Journal of the Rubber Research Institute of Sri Lanka
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Item Development of an early detection method for white root diseae of rubber: a preliminary investigation(Rubber Research Institute of Sri Lanka, 2011) Fernando, T H P S; Jayasinghe, C K; Siriwardene, DWhite root disease is the most destructive root disease of rubber in Sri Lanka and the rubber growers are confronted with the problem of early detection of this disease. The present study was aimed at investigating the possible early detection techniques to increase the effectiveness of chemical control programmes. The artificial inoculation of the plants was faster with naturally infected root inocula than the artificially prepared inocula. Fourteen weeks after mulching, all the plants under investigation showed rhizomorphs on the collar region while only 30% of the infected plants kept without mulching showed the rhizomorphs on the collar region. The rapid upward movement of the fungus in the presence of a mulch is shown to be useful for early detection of the white root disease.Item The performance of an accelerated drying system for drying of skim natural rubber laces(Rubber Research Institute of Sri Lanka, 2011) Siriwardene, S; Sarath Kumara, P H; Priyanka, U M SA dryer consisting of a saw dust fed furnace and a drying chamber was designed and fabricated for drying of skim natural rubber laces using hot smoke. Uninterrupted drying of laces was carried out in warm smoke in three different temperature ranges. Drying performance was evaluated in terms of raw rubber properties and drying period to achieve complete dryness. Quality of laces was assessed by visual appearance. The best temperature range for drying of skim natural rubber laces was found to be 30-34 0C. Drying efficiency of laces was accelerated by more than 60% without affecting its raw rubber properties when laces were dried at this temperature range. The resistance to mould growth of dried laces was also improved. However, the dried product was downgraded according to the visual quality assessment in terms of colour which is commonly practiced in the trade for grading of rubber. Therefore, heating mechanism was modified to provide a draft of clean warm air into the drying chambers where the laces were hung for drying. The drying temperature inside the chambers was maintained at the selected temperature range (30 -34 0C) and drying of laces was completed within twenty-four hours. It was able to obtain skim laces with improved colour. Drying curve for skim laces dried using accelerated drying system was derived. Results of tests carried out to determine the raw rubber properties of laces showed that raw rubber properties of skim laces were not affected due to accelerated drying within the selected temperature range. Mechanical and physical properties of 80/20 (w/w) blends of Technically Specified Rubber (TSR 20)/ambient air dried skim laces and the blends of TSR (20)/warm air dried skim laces were also compared. The properties studied were tensile properties, hardness, compression set and resilience. The results suggest that warm air drying of skim laces has no significant effect on the mechanical and physical properties of the blends of TSR/skim laces.Item Constraints in sustainable smallholder rubber farming in the Moneragala district(Rubber Research Institute of Sri Lanka, 2011) Wijesuriya, Wasana; Dissanayake, D.M.A.P.; Herath, H M L K; Gunaratne, P K K SThis study was focused on the Moneragala district which is one of the districts in the Uva Province. Rubber cultivation, being a new initiative there is a high risk of resource wastage in these areas which necessitated a detail study for proper planning of this exercise. Hence, the objective of this study was to assess the existing status of rubber cultivation in this area together with socio-economic conditions of rubber farmers. A questionnaire survey was done to collect relevant information from 255, 248 and 143 respondents in the respective categories of farmers who are prepared to cultivate rubber (potential farmers) and those who own immature and mature rubber plantations. Participatory studies were also done to assess the awareness on technical recommendations of rubber. The technical efficiency of rubber farmers was studied employing a stochastic frontier approach. More than 50% of the farmers had only primary level education. Hence, education needs to be considered as a constraint in improving the awareness of rubber farmers. Higher percentage of farmers with a monthly income of less than Rs. 10,000 should also be regarded as a bottleneck for the adoption of recommended technologies. Awareness on recommendations in immature phase ranged from 19% to 55% which was not at a satisfactory level. The awareness on tapping related activities was also not adequate since the awareness scores for both general and technical knowledge on tapping were below 40%. The production efficiency levels of mature rubber lands ranged from 17% to 96%, with an average value of 59%. The lands with smaller extent have lower efficiency levels. Those who practice the recommended tapping intensity had high efficiency levels. The average efficiency observed in the virgin panel was 62% while it was 52% with the renewed panels. The average efficiency in the lands tapped by owners themselves was 61% while when tappers were hired it was only 55%.Item Land suitability model for rubber in Moneragala district: first approximation using GIS(Rubber Research Institute of Sri Lanka, 2011) Karunaratne, Senani; Gunathilake, Jagath; Wijesuriya, Wasana; Herath, Keminda; Smarappuli, LalaniRubber is one of the major plantation crops grown in Sri Lanka, which generates foreign earnings to the country. To cope up with the increasing demand for rubber in both local and international markets it is vital to increase the extent under rubber cultivation. Expansion of rubber into intermediate and dry zone areas of Sri Lanka is focused in rubber development activities to achieve the national production targets. Hence, the objective of this study is to develop a land suitability map for rubber in Moneragala district and to identify potential land uses for further expansion of rubber in this district. The study was carried out in GIS environment using weighted overlaying technique. Results from the suitability analysis revealed that, the DS division, Madulla has the highest extent of ‘most suitable’ category (1289 ha) while Wellawaya and Siyambalanduwa have 480 ha and 476 ha, respectively. The information derived through this study offer a ground for the policy makers for effective decision making on expanding rubber cultivation in the Moneragala district.Item Carbon sequestration in mature rubber (Hevea brasiliensis Muell. Arg.) plantations with genotypic comparison(Rubber Research Insitute of Sri Lanka, 2011) Munasinghe, E.S.; Rodrigo, V.H.L.; Karunathilake, P.K.W.Forests play a vital role in regulating the greenhouse gases, particularly the level of atmospheric CO2; hence planting forests has been identified as one of the main options available to mitigate the effects of climate change. Rubber (Hevea brasiliensis), being a multipurpose tree which provides an economically viable (in terms of both latex and timber production) and socially acceptable system, can be effectively used in participatory tree planting programmes. Although the availability of carbon in rubber trees has been assessed before, the potential capacity of sequestering atmospheric CO2 in mature rubber trees has not been quantified. Therefore the present study was geared towards this whilst characterizing the genotypic differences in CO2 sequestration. Two promising genotypes viz. RRIC121 and RRIC100, were selected for the study. CO2 assimilation rates of rubber leaves in three canopy strata under varying light levels were measured and parameters of photosynthetic light response curves (LRC) were estimated. Leaf area distribution and light attenuation within the canopy were also measured. With previous weather records on incident light, its availability at different canopy levels was estimated using existing ecophysiological models and then the photosynthetic rates at canopy level were estimated. Maximum rate of photosynthesis and quantum yield (photosynthetic efficiency) decreased with the increase in depth of the canopy whilst it was vice versa for the convexity of light response curve. In general, parameters of LRC were superior in RRIC 121 to RRIC 100. Irrespective of the clone, a greater proportion of leaves was found in the top than in the lowest stratum. Leaf area index in RRIC 121 was greater than RRIC 100 with values of 5.88 and 3.47, respectively. Light extinction coefficient was less in RRIC 121 allowing more light to penetrate through the canopy than in RRIC 100. The capability of sequestering atmospheric CO2 was greater in RRIC 121 than that in RRIC 100 with annual rates of 117 and 45 MTha-1, respectively. On average, mature rubber is capable of sequestering 81 MT of CO2 per hectare annually and, within the 24 years of mature phase, 1,296 MT of CO2 would be sequestered in a hectare of rubber.Item Effect of iron in processing water on quality of crepe rubber(Rubber Research Institute of Sri Lanka, 2011) Ratnayake, U.N.; Sarath Kumara, P.H.; Siriwardene, T.A.S.; Prasad, A.K.D.; Rohanadeepa, V.C.Latex crepe rubber is the purest form of natural rubber and contamination of crepe rubber with metal ions should be avoided to maintain the quality of the rubber, especially to prevent the oxidative aging during storage. The influence of iron in processing water on raw rubber properties of crepe rubber has been investigated. Our research has shown that most of the iron ions contaminated from the processing water were leached out during the production process. The remaining iron ions in the crepe rubber catalyse the thermo-oxidative degradation and thereby significantly affect the oxidative stability of the rubber. Combination effect of Fe3+ ions and aromatic thiol, which adds into natural rubber (NR) latex to bleach the yellow pigments in fractionated bleached (FB) crepe rubber, further reduced its resistance to thermal oxidation, measured by Plasticity Retention Index (PRI). Therefore, fractionated unbleached (FUB) crepe rubber has a better oxidative stability than fractionated bleached (FB) crepe rubber. Further investigations carried out to study the effect of oxidation state of iron showed that not only Fe3+ ions but also Fe2+ ions catalyses the oxidative degradation process of natural rubber (NR). Based on our experimental results, new specifications for total iron concentration in the processing water and maximum allowable iron concentration in latex crepe rubber have been proposed.Item Harvesting the rubber tree once in four days: a solution to current issues in the rubber industry in Sri Lanka(Rubber Research Institute of Sri Lanka, 2011) Rodrigo, V.H.L.; Kudaligama, K.V.V.S.; Fernando, K.M.E.P.; Yapa, P.A.J.Item Secondary characters and their association with latex yield in Hevea brasiliensis(Mull Arg.)(Rubber Research Institute. Agalawatta, 1988) Olapade, E.O.Ten Hevea clones developed at the Rubber Research Institute Of Nigeria (RRIN) and a control clone RRIM 600 were evaluated for their latex yield after six months of tapping. The mean dry latex yield recorded for each clone was correlated with their Juvenile secondary characters i. e Height, Girth and Plant Vigour at 18 months. Significant variability was exhibited by the clones in terms of yield with clone C 83 having the highest mean latex yield of 42.15 g/t/t/ while clone C 202 had the least mean yield of 22.73 g/t/t. The secondary characters i. e Hewight, Girth and Vigour were significantly positively correlated to themselves but all negatively correlasted to latex yield. However a spurious correlation was established between latex yield and the secondary characters. The implication of the results are discussedItem Effect of potassium and magnesium on growth of young Hevea brasiliensis(Rubber Research Institute. Agalawatta, 1988) Weerasuriya, S.M.; Yogaratnam, N.The effect of potassium and magnisium fertilisers on growth of young Hevea brasiliensis were studied using clones PB 86, RRIC 100, RRIC 103, and RRIC 121 with the objective of determining the requirement of these elements during the early phase of establishment of these clones. Three commercial fertilisers were evaluated as of magnesium. Potassium requirement of clone PB 86 during the first year was found to be approsimately 33g K/plant/year. It was found that clones. RRIC 100 and RRIC 121 needed higher amount of K than PB 86 for normal growth. Potassium application caused an overall reduction in growth of clone RRIC 103 where the soil K level was 0.07 me./100g suggesting that this level is adequate for this clone during its first year of growth. Total dry weight was significantly increased when Mg application was increased from 11 to 22g/plant/year in clone RRIC 103 but such effects were not seen in clones PB 86, RRIC 100 and RRIC 121Item Nutrition and fertilizer use in Hevea and associated covers in peninsular Malaysia - a review(Rubber Research Institute. Agalawatta, 1977) Pushparajah, E.The paper reviews some of the latest findings on nutrition of Hevea and effects of fertilizer on latex properties. It also considers work on increased efficiency in use of fertilisers. The latter includes studies on effect of fertilisers on soil properties and availability of fertiliser residues. The use of appropriate covers and their management to increase their efficiency is considered. Additionally, the influence of the covers on the nitrogen nutrition of Hevea is discussed. The information available indicates that the applications of inorganic N fertilisers could be avoided for up to 8-109 years of tapping, with consequent economic benefits.