to find out most suitable fertilizer combination for higher growth, yield and quality of Vetiver. Different proportions of organic and inorganic fertilizers such as inorganic fertilizer alone, compost: inorganic fertilizer (1:3), compost: inorganic fertilizer (1:1), compost: inorganic fertilizer (3:1), compost alone and control (top soil: sand-1:2) were used as treatments. Growth, yield, oil content and quality parameters were taken 9 months after planting. Compost: inorganic fertilizer (3:1) mixture showed significantly higher shoot and root dry weights, number of leaves and tillers at 9 months after planting. Compost: inorganic fertilizer (3:1) mixture also showed significantly higher amounts of β-Vetivenene, Khusimol, and Iso-valencinol contents compared to other treatments. Therefore, compost: inorganic fertilizer (3:1) could be used as optimal fertilizer mixture for higher biomass production, oil content and quality of Vetiver.

No abstract

A pot experiment in an open area was conducted in 2015 yala season at the Regional Rice Research Institute, Ambalantota, Sri Lanka to determine the effect of foliar application of nano calcite on yield, yield component and quality of rice (Oryza sataiva) variety, At 362. Treatments tested were 4 levels of nano calcite (40, 80, 120 and 160 ppm) and plant growth were estimated 30, 60 and 90 days after transplanting and grain yield at harvesting. The experiment followed the Randomized Complete Block Design with 3 replications. It was found that the application of nano calcite foliar fertilizer has significantly contributed to enhance growth, yield, seed quality and insect resistance in At 362. Plants treated with 120 ppm nano calcite had highest yield with highest performances of growth and seed quality attributes. The dates required for the 50% flowering was reduced by 6 days and yield was increased by 25% with the application of 120 ppm nano calcite compared to the untreated plants. The plants treated with 160 ppm foliar nano calcite recorded significantly low gall midge damage, leaf mites, stem borer damage and paddy bugs as compared to untreated control and treated with lower doses (40 and 80 ppm). While the data of this study showed that nano calcite has positive effects on rice growth, yield and induced resistance to insect pests, further research would be needed to validate the observations.

Pterocarpus santalinus Linn.) is an evergreen tree species grown under semi dry climates in well drained lateric soils. The reddish and fragrant heartwood has a range of medicinal, pharmaceutical, industrial and timber and economically placed in the same category as tusk and amber. The Red heartwood contains a range of constituents including santalin (Santalic Acid), Santaol, Pterocarpin, Homo-Petrocarpin and reported to have anticoagulant, anti inflammatory, anti expectorant, anti pyretic, anti bacterial and anti tumor properties. Expensive natural fabric paint produced from the powdered Red heartwood is used in wood carving of prestigious nature. The natural habitat of Red Sandalwood is India which is extensively exploited to the point of near extinction, thus placing it in the red list of endangered species under IUCN guidelines.

The aim of this study was to assess the impact of natural rubber tire waste charcoal (NRTWC) amendment on carbon mineralization in tea cultivated soils in low country wet zone of Sri Lanka. NRTWC was applied at different rates (0%, 1%, 1.6%, 2.2% and 2.8% w/w) and carbon mineralization in soil was evaluated at 10 and 20 weeks after the treatment. Representative samples were incubated for 42 days and microbial respiration was determined. During the first seven days of incubation, a rapid carbon mineralization was observed for all the treatments. A rapid decline of carbon mineralization was then observed during the period from 14 th to 28 th day of incubation. No changes were observed towards the end of the incubation (35 to 42 days). Significant (P ≤ 0.05) differences among the different rates of NRTWC application were noticed during the initial stages of the incubation. However, the variations were minimal after 14 th day of the incubation. The cumulative carbon mineralization ranged from 506 to 1072 mg/kg soil for the samples taken at 10 weeks after treatment. The corresponding variation changed from 506 to 1730 mg/kg soil for the samples drawn at 20 weeks after treatment. The cumulative soil carbon mineralization increased rapidly during the early stages, then decreased gradually and finally flattened out towards the end of the incubation. The application of NRTWC resulted in a substantial increase in cumulative carbon mineralization when compared with the control. As revealed by the results, NRTWC decomposes slowly and can be considered as a sound source of soil amendment which could enhance soil carbon sequestration in degraded tea soils.