University of Colombo e-Repository

UCER (University of Colombo Electronic Repository) is a collection of scientific research publications by researchers at the University of Colombo, Sri Lanka. This e-Repository serves to manage, preserve and make available the academic works of the faculty, postgraduate students, and research groups. The collection includes faculty publications, master's and doctoral theses abstracts. This repository is updated regularly, and new works are added to collections on a continuous basis

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Authors are responsible for obtaining copyright permission from the publisher and submitting the signed declaration to ir@lib.cmb.ac.lk.

Recent Submissions

Seasonal dynamics of leachate pollution potential at Kerawalapitiya Waste Park in Muthurajawela wetland, Sri Lanka; a Leachate Pollution Index study
(University of Colombo, 2025) Bandara, S.J.S.; Piyadasa, R.U.K.; Himanujahn, S.; Gunawardhana, E.R.
This study investigates seasonal variations in the potential of leachate contamination at Kerawalapitiya Waste Park; the largest open waste dump located in Muthurajawela wetland. The study measured contamination potential across three seasonal periods through the Leachate Pollution Index (LPI) during a three-year monitoring period from 2022 to 2024 with 36 samples collected monthly. This study evaluated multiple physicochemical parameters including organic pollutants (BOD₅, COD), inorganic components (pH, EC, TDS), heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn, Fe, Mn), major cations and anions, and nutrient indicators (NH4+, NO₃-, PO₄3-) to emphasize environmental contamination threats to the nearby wetland ecosystem. The study confirmed key differences in potential of leachate pollution among seasons, based on the precipitation levels while total LPI values ranged from 10.0 during the 2023 wet season, (monthly rainfall around 1000 ml) to 37.2 during the 2024 dry season (monthly rainfall less than 300 ml) which indicated moderate to high contamination levels that surpassed environmental standards. The main pollution source consisted of organic matter which reached its maximum level of 80.0 during the 2024 intermediate season (monthly rainfall nearly 500 - 600 ml) although heavy metal contamination showed unpredictable behavior with its highest level of 43.8 during the 2024 dry season. The study revealed that 2024 signified the most hazardous year for the environment since all measured components showed in high contamination levels. The seasonal examination of the monitoring period showed irregular patterns which imply that traditional seasonal management techniques are insufficient for handling intricate relationships between climatic elements and waste composition as well as leachate generation methods. The results emphasize an immediate requirement for improved surveillance procedures along with flexible strategies of pollution management which can be adapted to time-based changes in composition of contamination. This study shows that leachate pollution potential peaks during dry seasons, underscoring the need for season-specific monitoring and treatment strategies to protect the Muthurajawela wetland.
Impact of different concentrations of gibberellic acid on the growth and yield of rice (Oryza sativa L.) under Low Country Dry Zone of Sri Lanka
(University of Colombo, 2025) Madhushika, D.W.N.; Nawarathna, S.L.; Siriwardena, M.H.U.; Kumara, K.H.C.H.
This study focuses on identifying the optimal gibberellic acid concentration to enhance rice productivity in semi-arid conditions while identifying the impact of different concentrations of gibberellic acid on growth and yield of rice. Growth regulators, such as gibberellic acid, play a crucial role in optimizing crop growth, improving yield and mitigating the effect of environmental stress. This experiment was conducted at the rice research station in Ambalantota during the “Yala” season in 2024. The experiment utilized the At362 rice variety. The experimental design was randomized complete block design (RCBD) with four replicates, and included six gibberellic acid treatments (0 ppm, 25 ppm, 50 ppm, 75 ppm,100 ppm,125 ppm). In this experiment, 15 ml of gibberellic acid solution was applied to the plant. This application was done four weeks after planting. The plant was separated before application. Results indicated significant differences in plant growth parameters and yield components with the 75 ppm treatment producing the highest plant height (104.09 cm), number of tillers (7.6), and number of filled grain panicles (76.27) leading to optimal grain yield (20.60 g). Conversely, higher concentrations (100 ppm, and 125 ppm) negatively affected these parameters, resulting in reduced performance, particularly in yield. The findings highlight gibberellic acid potential as a vital plant hormone in enhancing rice growth and yield, particularly under challenging climatic conditions.
Evaluating the effect of different fertilizer formulations on pod filling in the groundnut variety “Lanka Jumbo”
(University of Colombo, 2025) Vijesuriya, K.H.M.S.S.; Ratnayaka, U.A.J.; Siriwardana, A.J.M.C.M.; Rifnas, L.M.
Lanka Jumbo is a popular medium-duration jumbo peanut (Arachis hypogaea L.) variety released by GLORDC, Angunakolapelessa, Sri Lanka. Pod filling is a crucial phase in groundnut development, significantly affecting yield and plant health. Calcium plays a key role in pod formation, yield improvement, and nutritional quality. This study aimed to identify an optimal fertilizer mix to enhance pod filling and increase the yield of groundnut variety Lanka Jumbo. A field experiment was conducted in Rideemaliyadda, Badulla district (IL2 Agro-ecological zone), Sri Lanka, to evaluate the effectiveness of seven fertilizer treatments. The Department of Agriculture (DOA) Sri Lanka recommendation (T1 - Urea 65 kg/ha, TSP 100 kg/ha, MOP 75 kg/ha) was compared with six alternatives: a 20% increase in TSP and MOP (T2), 250 kg/ha gypsum with enhanced nutrients (T3), gypsum with the DOA recommendation (T4), DOA recommendation + 500 kg/ha Nutri Pellets compost (T5), Commercially available complex fertilizer (125 kg/ha) + Commercially available calcium nitrate and boron mix fertilizer (62.5 kg/ha) (T6), and DOA recommendation + nitrogen foliar spray (T7). Treatments were arranged in a Randomized Complete Block Design (RCBD) with three replicates. Plant height and the number of branches per plant were recorded as plant growth data at 25 and 60 days after planting, while yield parameters included the number of pods per plant, the number of filled and unfilled pods per plant, and the dry weight of 100 seeds. No significant differences in plant growth were observed among treatments at 60 days after planting, although T7 recorded the highest plant height (58.7 cm) and number of branches (9.6). T4 showed the best yield performance, producing 134.67 g of dry pod weight per plant, with 53.3 pods per plant, a 96.2% pod filling rate, and a 100-seed weight of 210 g. In contrast, T7 had the lowest performance, with 40.7 pods per plant and a significantly lower pod filling rate (39.3%). These findings suggest that applying 250 kg of gypsum with the DOA-recommended fertilizer mixture improves pod filling and enhances the yield of groundnut var. Lanka Jumbo.
Influence of growing media and planting techniques on the growth of young budding rubber plants under nursery conditions
(University of Colombo, 2025) Chandrasena, K.K.L.S.; Nakandala, S.A.; Udayakumari, U.N.; Bandusekara, B.S.
Physical, chemical, and biological characteristics of the growing medium significantly influence the growth and development of young rubber plants. In many rubber nurseries, the availability of fertile topsoil is limited due to the repeated establishment of large-scale nurseries in the same area over extended periods and therefore, nursery operators often resort to using subsoil as a growing medium, which is high in clay, low in organic carbon, and exhibits poor physical structure. Although their chemical fertility can be enhanced through the application of fertilizers, unfavorable soil physical properties continue to hinder optimal plant growth. Therefore, this study is based on enhancing the quality of the potting medium, along with the adoption of improved planting techniques. An experiment was conducted in a rubber nursery with 5000 plants using a Randomized Complete Block Design with two factors: five growing media (T1 – Soil mixture (control), T2 - Soil mixture: Coir pith=1:1, T3 - Soil mixture: Burnt Rice Husk=1:1, T4 - Soil mixture: Coir pith: Burnt Rice Husk=2:1:1, T5 - Soil mixture: Coir pith: Compost=2:1:1) and two planting techniques (trench planting with coir pith (WC) and trench planting without coir pith (WOC)). Growth attributes, i.e., stem diameter, plant height, leaf area, root length, chlorophyll content, and stomatal conductance were measured throughout the period. Dry matter analysis was done using standardized methods. The results revealed significant (p < 0.05) variation in plant growth attributes under different treatments and planting techniques. Coir-based media, particularly T2 (coir pith: soil) and T5 (coir pith: compost: soil), promoted larger leaf area (2890.5 cm2) and greater stem diameter (7.8mm), enhancing shoot and leaf growth. The T3 (coir: rice husk) mixture was particularly effective in root development, producing the longest taproots and highest root weights. Trench planting with coir pith consistently yielded higher growth compared to WOC. Additionally, coir-based media demonstrated 25% - 27% water retention, making them ideal for water-scarce environments. These findings suggest that coir-based growing media and trench planting techniques are practical and efficient solutions for enhancing plant growth, making them valuable strategies for optimizing nurseries in challenging environments.
Effects of variable seed rates and potassium levels on yield components and quality parameters of Basmati Type No. 06 rice in Sri Lanka
(University of Colombo, 2025) Herath, H.M.K.G.S.S.K.; Jayaprada, N.V.T.; Priyantha, W.S.
Basmati rice is known for its fragrance, long grains, and excellent cooking qualities. This study was conducted to identify the suitable seed rate and potassium fertilizer combination to achieve the maximum grain yield and quality of Basmati type No.06 rice variety. A field experiment was carried out at CIC seed farm, Pelwehera, Sri Lanka from May 2024 to August 2024. The study had nine treatments (T1- 45 g/plot + Department of Agriculture recommended Muriate of Potash [DoA MoP], T2- 45 g/plot + 1 ½ DoA MoP, T3 – 45 g/plot + no MoP, T4 – 90 g/plot + DoA MoP, T5 – 90 g/plot + 1 ½ DoA MoP, T6 – 90 g/plot + no MoP), T7 – 135 g/plot + DoA MoP - control, T8 – 135 g/plot + 1 ½ DoA MoP and T9 – 135 g/plot + no MoP) in a Randomized Complete Block Design (RCBD) with three plot replications with a plot area of 18 m2. Based on the ANOVA results, selected combinations of seed rates and MoP levels did not have a significant effect (p>0.05) on vegetative growth and actual yield. The effect was significant (p<0.05) on grain quality characters. A moderate seed rate of 90 g per plot (one bushel per acre) combined with 1½ of the DOA recommended MOP had the best performance in terms of grain physical quality, with a significant (p<0.05) maximum grain length (8.04±0.05 mm). It also showed superior milling quality, with a significant (p<0.05) higher head grain percentage (35.03±0.37 %) and a significant (p<0.05) lower broken grains percentage (33.56±0.45 %), along with excellent cooking quality, including a significant (p<0.05) longer grain length after cooking (12.23±0.03 mm) and an elongation ratio of 1.52±0.01. Based on these findings, the study concludes that using a 90g seed rate per plot (one bushel per acre) with 1½ of the DOA recommended MOP is the optimal combination to achieve maximum yield and quality for Basmati type no. 06 rice variety. However, the research should be replicated and tested in other agro-ecological zones in Sri Lanka during both Yala and Maha seasons to validate the findings.