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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 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 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 Performance of some RRIC 100 series clones under different soil moisture regimes(Rubber Research Institute:Agalawatta, 1992) Samarappuli, L.; Yogaratnam, N.; Hettiarachchi, R.Results obtained on the performance of recently developed RRIC 100 series clones when sujected to water deficit situations are presented in this paper. The plant diameter of RRIC 121 and RRIC 102 was found to be superior to other clones tested such as RRIC 100, RRIC 110 and PB 86 even at the very low soil moisture level of 10% available water. Similar results were recorded in relation to plan height, number of whorls and relative growth rates of clones RRIC 121 and 102 even under low soil moisture conditions. Data obtained also showed that clones RRIC 102 and 121 had the highest plant nitrogen and potassium contents. Moreover, even under very low soil moisture levels plant P content was greater in clones RRIC 121 and 102. Most of the data on growth are also consistat with the physiological parameters such as leaf water protential (LWP) relative water content (RWC), transpiration rate (TR) and leaf diffusive resistance (LDR). It was further noted that the LWP and RWC were highest while TR was lowest in clone RRIC 102. Moreover, the clone RRIC 102 had the highest LDR compared to other clones, confirming the ability of this clone in maintaining a higher water holding capacity under low soil moisture conditions.Item Towards shorter immaturity and improved yields by mulching with rice straw(Rubber Research Institute:Agalawatta, 1992) Samarappuli, L.; Yogaratnam, N.; Samarappuli, P.; Mitrasena, U.In this study with immature Hevea brasiliensis, multing with paady straw around the base of the tree was found to be a better agronomic practice than growing leguminous cover crops such as Pueraria phaseoloides and Desmodium ovalifolium or allowing natural vegetation to grow in the inter-row area. Girthing had been much higher with mulching which resulted into reduction of the immature, unproductive period by approximately 18 and 12 month in comparison with naturals and creeping legumes respectively. In addition to early tapping, yield of latex was also higher during the early stages, increases in the region of 33perc. and 40perc. in comparison with creeping legumes and naturals respectively. The present value of the benefit achieved from mulching amount to Rs. 31,088/= per hectare of which Rs. 19,740/= is due to extra yield and the balance of Rs. 11,348/= is saving on inputs as a result of early maturity. Consequently, a net present value (NPV) of Rs. 7.8 million at national level can be achieved with the above practice at 50perc. level of adoptionItem Fertilizer use among perennial crops(Rubber Research Institute of Sri Lanka:Agalawaththa, 1982) Peries, O.S.; Yogarathnam, N.Item Cinnamon (Cinnamomum verum J. Pres) intercropped under different inter row spacings of rubber (Hevea brasiliensis Muell. Arg.). performance after rubber reached maturity(Rubber Research Institute:Agalawatta, 2007) Pathiratna, L.S.S.; Perera, M.K.P.; Balasooriya, C.K.Item The response of yields of clones RRIC 100 and RRIC 121 to the changes in the distribution and amount of rainfall(Rubber Research Institute:Agalawatta, 2007) Withanage, S.P.; Kumara, I.D.M.J.S.; Kariyawasam, L.S.Item Enjoy 2000 plus yields. adhere to basic agronomic practices(Rubber Research Institute of Sri Lanka:Agalawatta, 2006) Nugawela, A.Item Stimulation of rubber trees for enhancing performance - the past, current practices and future trends(Rubber Research Institute of Sri Lanka:Agalawatta, 2006) Nugawela, A.