Journal of the Rubber Research Institute of Sri Lanka
Permanent URI for this collectionhttps://dl-rri.nsf.gov.lk/handle/1/1399
Browse
8 results
Search Results
Item 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 Effects of pottasium and magnesium on leaf and bark nutrient contents of young Hevea brasiliensis(Rubber Research Institute. Agalawatta, 1989) Weerasuriya, S.M.; Yogaratnam, N.Leaf and bark analyses provide evidence of uptake of K and Mg from applied K and Mg fertilisers respectively. Efficiency of uptake appears to have however been influenced by the level of applied K and Mg, pre - treatment K and Mg content of the soil and sources of Mg. Significant antagonistic effects between K and Mg fertilisers on leaf K and Mg have been recorded. Both K and Mg fertilisers were also found to decrease the Ca content in the leaf except when dolomite was used as the source of Mg. It appears that bark analyses could also be used as a tool for indicating the K and Mg status of young Hevea plantsItem Ferilizer responses in mature Hevea under Sri Lankan conditions(Rubber Research Institute. Agalawatte, 1984) Yogaratnam, N.; Weerasuriya, S.M.The results of three out of a series of eight experiments that have been in progress (most of them) since 1976, are discussed. Yield increases in the existing plantations could be obtained with increased applications of nitrogen fertilizers in the form of urea. The level of application could be increased to double that of the currenly recommended rate. Some yield increases were also obtained with applications of potassium. It has also been shown that application of rock phosphate to mature rubber trees is not always benificial. Similary, applications of magnesium containing fertilizers to mature rubber should not also be made indiscriminately. Although the leaf K concentration showed K deficiency in one experiments, application of potassium has increased the K may have to be clone specific and at least for the clone RRIC 45, the leaf K levels may have to be reviced. In general, fertilizer application to mature rubber with complete NPKMg mixtures, may not be economically justified, particular ly in the present context of fertilizers and rubber price. The results reported have covered only parts of the planting cycles following fertilizers application. The experiments are still in progress and will be continued at least until the responses have stabilized. A detailed economic analysis at the end of this period would then give a more realistic picture on the economics of fertilizer application for mature rubber under Sri Lankan agro-climatic conditionsItem Fertilizer responses in Hevea brasiliensis seedings grown in the field nursery(Rubber Research Institute. Agalawatta, 1972) Yogaratnam, N.; Karunaratne, A.D.M.Item Weed control under Hevea in Ceylon with herbicide mixtures based on MSMA(Rubber Research Institute. Agalawatta, 1971) Yogaratnam, N.Item Urea as a source of nitrogen for rubber plantations in Sri Lanka I.. a review and preliminary observations(Rubber Research Institute Sri Lanka. Agalawaththa, 1981) Yogaratnam, N.Item Effect of fertilizers on leaf composition of N.P.K. in some Hevea cultivars(Rubber Research Institute. Agalawatta, 1985) Yogaratnam, N.; De Mel, J.D.Item 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.