Browsing by Author "Nugawela, A."

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Budwood nurseries in Sri Lanka. condition of the nureseries in the estate sector
(Rubber Research Institute. Agalawatta, 2000) Seneviratne, P.; Nugawela, A.; Weerakoon, U.S.; Alwis, M.N.De.; Zoysa, L.
Can D/3 frequency tapping minimize problems related to tapper shortage
(Rubber Research Institute. Agalawatta, 1998) Nugawela, A.; Peries, M.R.C.; Wijesekera, S.; Wilbert, S.
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.
The correlation between branching and the tree growth of Hevea brasiliensis (Muell.Arg.)
(Rubber Research Institute of Sri Lanka. Agalawatte, 1996) Seneviratne, P.; Nugawela, A.; Ramawickrama, D.
The main objective of the present study was to see whether there is a correlation between the number of branches and the tree grwoth in hevea brasiliensis. Considerable variation in brancing habits is observed among the trees of different clones. Also, some clones such as RRIC 121 show less brancing when compared to other clones such as RRIC 100 indicating brancing is also a clonal characteristic. Canopy architecture too, shows differences among trees within a clone. Highly significant positive correlation was observed between the number of branches and the tree girth for all clones tested for trees aged from one year to seven years. The correlation between the canopy distribution (grouped as very good, good or poor) and the tree girth was also positive.
The crop loss due to wet weather and methods to overcome it
(Rubber Research Institute. Agalawatta, 1999) Nugawela, A.
Deep planting for better performance
(Rubber Research Institute. Agalawatte, 1996) Seneviratne, P.; Nugawela, A.; Samarakoon, S.M.A.
Diurnal variation in gas exchange characters of leaves of Hevea brasiliensis exposed to sun light at different canopy levels and their contribution to dry matter production
(Rubber Research Institute of Sri Lanka. Agalawatte, 1995) Nugawela, A.; Abeysinghe, D.C.A.; Samarasekera, R.K.
As in many other crops a significant percentage of leaves in the canopy of a rubber plantation are found under limiting light levels. The photosynthetic capacity of these shaded leaves may play an important role in determining the productivity of the rubber plants. The dry matter production capacity of shade leaves was srudied using polybag plants of Hevea brasiliensis and grown under different light regimes. The CO2 assimilation rates and related parameters were monitored through-out the day using a portable photosynthesis system. The diurnal variation pattern of CO2 assimilation rates and the internal leaf CO2 concentration to ambient CO2 concentration ratio (ci/ca) were different in plants grown under different light regimes. Though peak CO2 assimilation rates are shown at around 0930h in all treatments, the assimilation rates tend to decline very early in plants grown under full light. During the early and latter parts of the day, plants grown under full light showed significantly higher CO2 assimilation rates than in plants grown under 40 per cent and 25 per cent of incident light. However, stomatal conductance declined with time of the day and it was similar in all treatments. Low CO2 assimilation rates later in the day could be either due to accumulation of abscisic acid or due to end product inhibition. It is apparent that photosynthesis is only marginally high during the major part of the day, ie 0930h - 1430h in plants grown in full light. Therfore, sun and shde leves may be comparable as the daily photosynthetic integral and hence the dry matter production is concerned. Thus, shaded leaves in rubber plantations may significantly contribute to the total dry matter production of the plant.
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 same
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.
The effect of girth at opening on yield and growth of modern Hevea brasiliensis Muell Arg. clones
(Rubber Research Institute. Agalawatta, 2002) Nugawela, A.; Samarasekera, R.K.; Wilbert, S.
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.
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.
The effect of the condition of budwood nurseries on the productivity. mixed clones
(Rubber Research Institute of Sri Lanka. Agalawatta, 2000) Seneviratne, P.; Nugawela, A.; Weerakoon, U.S.; De Alwis, M.N.
Effective and efficient exploitation of higher virgin panels in Hevea brasiliensis Muell.Arg
(Rubber Research Institute of Sri Lanka. Agalawatta, 1999) Nugawela, A.
Effectiveness of low frequency harvesting systems in rubber smallholder sector of Eastern province (IL2) of Sri Lanka
(Rubber Research Institute:Agalawatta, 2016) Lakshman, R.G.N.; Kudaligama, K.V.V.S.; Rodrigo, V.H.L.; Nugawela, A.; Attanayake, A.P.; Perera, M.K.P.; Madushani, P.D.T.L.
Enjoy 2000 plus yields. adhere to basic agronomic practices
(Rubber Research Institute of Sri Lanka. Agalawatta, 2006) Nugawela, A.
Exploitation and stimulation recommendations in Sri Lanka
(Rubber Research Institute . Agalawatte, 1996) Tillekeratna, L.M.K.; Nugawela, A.
Exploitation systems for some hevea brasiliensis muell arg clones for improved economic performance
(Postgraduate Institute of Agriculture, University of Peradeniya:Peradeniya, 2002) Gunasekera, H.K.L.K.; Nugawela, A.; de Costa, W.A.J.M.; Attanayake, D.P.S.T.G.
Factors affecting the budgrafting success and the scion growth of young budding of Hevea
(Rubber Research Institute. Agalawatta, 1994) Seneviratne, P.; Nugawela, A.; Samarakoon, S.M.A.
The size of the bag in which the stock plant is grown seems to have an effect on the growth of the seedling; from the three bag sizes tested, ie 15 x33 cm, 18 x 38 cm, 23 x 45 cm, it was found that the diameter the number of leaf whorls of the seedling increased with the increase of the bag size.Though the differences are not statistically significant, the budding success too increased in the same pattern. There was no effect of the bag size on the growth of the scion. The two types of buds, axillary scale, showed no difference either on bud grafting success or on the growth of the scion. The growth stage of the top most leaf whorl of the stock plant, either mature or immature, had no effect on the peeling qualities budgrafting success though a little higher budgrafting success was seen when the top flush was immature. There was an effect of the snag, on the scion growth; when the snag was shorter the sprouting took place earlier but, the scion growth was slightly poor as was evident by the diameter the length of the scion. Long snags delayed the sprouting , but the scion growth was better. The best growth of the scion was obtained when the snag was long with a few leaves attached to it.
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.