Journal of the Rubber Research Institute of Sri Lanka

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Author: search.filters.author.Yogaratnam, N.Subject: search.filters.subject.Plant growth

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    Effect of soil moisture on establishment success of different planting techniques in rubber
    (Rubber Research Institute. Agalawatta, 1993) Samarappuli, L.; Yogaratnam, N.; Hettiarachchi, R.
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    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.
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    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 adoption
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    Effect of potassium on growth, yield and mineral composition of young Hevea brasiliensis
    (Rubber Research Institute of Sri Lanka. Agalawatte, 1995) Iqbal, S.M.M.; Yogaratnam, N.
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    Management of covers under Hevea in Sri Lanka
    (Rubber Research Institute. Agalawatta, 1977) Yogaratnam, N.; Sulaiman, H.; Karunaratne, A.D.M.; Peiris, K.S.A.C.
    Results of two experiments, comparing the effects of leguminous creepers and naturals as ground covers on growth of immature rubber, are discussed. In one experiment the growthof rubber in plots under pure legume covers was better than that under naturals. Applications of extra nitrogen to trees in plots with natural covers improved their growth but the latter was not comparable to that in legume plots. In the pther experiments the increase in growth of rubber with higher levels of fertiliser nitrogen was observed irrespective of the type of cover. Application of phosphate to covers led to better tree girths than where the phosphate was applied on the trees, irrespective of the type of cover grown. These results are discussed in relation to the nitrogen content of rubber eaves, green matter, litter and C/N ratio of the litter of cover.