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Item Effect of recovery tapping on yield potential of rubber (Hevea brasiliensis) trees(Rubber Research Institute:Agalawatta, 2001) Silva, T.U.K.; Nugawela, A.; Rodrigo, V.H.L.; Serasinghe, P.Item Rubber cum sugarcane intercropping. a sustainable cropping system for farmers in the intermediate zone of Sri Lanka(Rubber Research Institute:Agalawatta, 2000) Rodrigo, V.H.L.; Nugawela, A.; Sivanathan, A.; Witharama, W.R.G.; Jayasinghe, W.K.Item Shade effects on photosynthesis of cinnamon (Cinnamomum verum J. Pres)(Rubber Research Institute:Agalawatta, 1998) Pathirana, L.S.S.; Nugawela, A.; Samarasekera, R.K.Item Shade effects on photosynthesis of cinnamon (Cinnamomum verum J. Pres)(Rubber Research Institute:Agalawatta, 1998) Pathirana, L.S.S.; Nugawela, A.; Samarasekera, R.K.Item Field performance of young coffee seedlings and cuttings intercropped with rubber(Rubber Research Institute:Agalawatta, 1988) Rodrigo, V.H.L.; Nugawela, A.; Kariyawasam, L.S.; Aluthhewage, R.K.Coffee may be planted either using seedlings or cuttings. Anyhow, a comparative study of their field establishment and performance has not been made. Iin this study seedlings and cuttings of Coffea canephora intercropped with rubber were compared for their field stablishment and growth. It is evident that there is no difference in the success of their field establishment. The dry matter yield determinants of plants, i. e. light intercept ion, conversion efficiency and rate of loss of dry matter, estimated by total leaf area, CO2 assimilation rate and dark respiratory rate respectively, are also similar in both seedlings and cuttings. This is confirmed by the similar mean total dry weight of a seedlings and a cuttings. The partitioning of assimilates is more towards root development in the cuttings and is evident by the significantly high root dry weight and the root/shoot ratio. The percentage of assimilates partitioning towards the growth of aerial parts is less in the cuttings, i. e. 52 and 67perc. for cuttings and seedlings respectively. Despite of similar light levels, the CO2 assimilation rates are lower in the afternoon in both seedlings and cuttings. The perc. deeline is 23.5 and 18.6perc. for seedlings and cuttings respectively.Item Clonal differences in growth parameters of young Hevea buddings and their relation to field performance(Rubber Research Institute:Agalawatta, 1986) Nugawela, A.; Aluthhewage, R.K.Hevea trees when tapped exhibited a depression of girth increment and canopy growth. Hence a high growth rate is required to maintain the growth whilst giving a high yield. Growth parameters of 5 Hevea clonal buddings were determined after different growth intervals viz., 3, 6 , 9, and 12 months to study the correlation they show with the field performance of the same clones. Clonal differences were significant, but did not necessarily correlate with the field performance. Growth rates gradually increased with age during the peeriod of investigatiion. Thepossibility of using growth parameters together with gas exchange capacities determinedin earlier studies in predicting later field performance are discussed.Item Effect of different levels of supplemental nitrogen on CO2 assimilation rates and productivity of Pueraria phaseoloides (Roxb) Benth and Desmodium ovalipolium (prain) wall. ex ridely grown in agalawatta series soil(Rubber Research Institute:Agalawatte, 1985) Nugawela, A.; Jayasinghe, C.K.; Aluthhewage, R.; Wettasinghe, S.Plant dry matter production is linked to CO2 assimilation rates, respiratory losses and total leaf area. Experiments were undertaken to determine the effect of different levels of supplimental nitrogen given to legume cover crops, on their CO2 assimilation rates and productivity. They were found to be highest for Pueraria phaseoloides and Desmodium ovaliforlium when given around 140 and 35 ppm of supplimental nitrogen. Reciprocal of specific leaf area and laef nitrogen content were also determined and they showed a positive linear relationship with supplemental nitrogen levels. How nitrogen could a influence the CO2 assimilation rates of cover crops studies are discussed.Item The effect of tapping on the assimilation rates of Hevea brasiliensis Muell. Arg. leaves(Rubber Research Institute:Agalawatta, 1990) Nugawela, A.; Aluthhewage, R.K.The CO2 assimilation rates at leaf level were compared in tapped and untaped trees of two Hevea brasiliensis genotypes. In both genotypes, the CO2 assimilation rates of the leaves in the upper stratum were lower in tapped trees. Simmilary, in young microtapped plants the CO2 assimilation rates were lower than in the untapped plants. The decrease in CO2 assimilation rates due to tapping cannot be attributed to an increase in either stomatal or mesophyll limitations. Tapping increases the sink demand for photo assimilates, but it also results in the loss of water, inorganic nutrients and proteins from the plant. Loss of water, inorganic nutrients may results in lower CO2 assimilation rates of the tapped trees. In the long-term this could result in lower sucrose content in the latex. This may be a probable cause for the physiological disorder, tapping panel dryness in rubber.Item An economic evaluation of the use of rainguards(Rubber Research Institute:Agalawatta, 1993) Rodrigo, V.H.L.; Herath, P.H.M.U.; Nugawela, A.Use of rainguards can minimize the loss of tappping days and hence the loss in rubber crop. A simple model was developed to study different components determinig the profitability of using rainguard is discussed. Price of rubber, yield potential of a plant and tapping wage rate were identified as most important factors which determine the worthiness of the use of rainguards. Sealent price is also a major factor in deciding profitability. If the price of scalent is less than Rs. 20/= per kg, the profilability from both the apron and the gutter types is sameItem Rubber research in Sri Lanka-the past 100 years and the future(Rubber Research Institue:Agalawatta, 2010) Nugawela, A.