16th Annual Research Symposium-2024

MORPHOLOGICAL CHARACTERIZATION OF SELECTED DIOSCOREA ACCESSIONS

Wed, 20 Nov 2024 00:00:00 GMT

MORPHOLOGICAL CHARACTERIZATION OF SELECTED DIOSCOREA ACCESSIONS Fernando, W.V.K.; Edirisinghe, E.S.C.; Egodawatta, W.C.P. Dioscorea, commonly known as yam, is one of the most important staple crops in the tropics, crucial for economic stability and food security. The Plant Genetic Resource Centre (PGRC) in Sri Lanka has conserved 215 Dioscorea accessions as of 2024, which have not been fully characterized yet. The main objective of this study was the morphological characterization of selected Dioscorea accessions conserved in the PGRC germplasm. All accessions were cultivated under standard homogeneous conditions for characterization during the period from June 2024 to November 2024. International standardized descriptors for yams were used to characterize 84 morphological characters from 25 accessions during the vegetative phase of Dioscorea, each grown in duplicate. The cluster analysis, cluster variations and descriptive statistics were obtained using SAS JMP Pro 18. No duplications of conserved germplasm at PGRC were observed, thus each accession was unique under morphological characters. Three distinct clusters were identified, while cluster 1 consisted of three accessions: BTD - 6, BTD - 67, and BTD – 243, all belonging to Dioscorea bulbifera. Cluster 2 contained six accessions belonging to Dioscorea esculenta, while cluster 3, Dioscorea alata was represented by 16 accessions and the cluster analysis explained 73.2% of variation using qualitative characters and 69.6% using quantitative characters. When both qualitative and quantitative characters were for clustering 72.6% of variation in the collection was explained without altering the clustering pattern. Clustering was largely based on young stem color, young stem wing color and hairiness on the mature stem as qualitative and young stem length, leaf measurements and number of branching (above ground) as quantitative characters. The finding of this study is useful for systematic germplasm conservation and the utilizing of prominent traits in yam varietal improvement programs. Future studies should aim to include reproductive and storage characteristics to broaden the application of these results.

MODELING FOR OPTIMIZING NITROGEN FERTILIZER RATES FOR MAIZE IN DRY ZONE OF SRI LANKA UNDER CURRENT AND FUTURE CLIMATE SCENARIOS

Wed, 20 Nov 2024 00:00:00 GMT

MODELING FOR OPTIMIZING NITROGEN FERTILIZER RATES FOR MAIZE IN DRY ZONE OF SRI LANKA UNDER CURRENT AND FUTURE CLIMATE SCENARIOS Uduwawala, H.; De Silva, S.H.N.P.; Egodawatta, W.C.P. Maize (Zea mays L.) is the most vital upland cereal and a cornerstone of food security in Sri Lanka. Despite its extent of cultivation within the dry zone, a region highly vulnerable to climate change vulnerabilities, the current nitrogen (N) fertilizer recommendations often lack climate-specific optimization, leading to inefficiencies in yield and environmental impacts. The objectives of this study were to model and optimize N fertilizer rates for maize, under current and projected climate conditions for 2050 and 2100 by testing different nitrogen management scenarios by utilizing the agricultural production systems simulator (APSIM). The analysis incorporated Department of Agriculture recommendations, present-day data, and climate projections, for examining yield, nitrogen leaching, and fertilizer rates across the Maha and Yala seasons under rain-fed conditions. Findings indicated that under current conditions, applying 345 kg ha-1 of N in the Maha season yields 2,625.10 kg ha-1 with a median leaching value of 11.3 kg ha-1. In Yala, 435 kg ha-1 of N achieves 3,174.46 kg ha-1 yield and 0.4 kg ha-1 leaching. As per anticipated alterations in climate scenarios for 2050, a slightly increased optimal yield is expected with similar N rates. In 2100, particularly in Yala, the simulated yield increased with higher N rates (375 kg ha-1 in Maha and 465 kg ha-1 in Yala), despite increased leaching. The study emphasized the importance of climate-responsive N management to sustain yield optimization and mitigate environmental impacts over time. This research provides data-driven insights for policymakers and extension services, highlighting the value of climate-resilient N management strategies for sustainable maize production. These tailored recommendations would help Sri Lankan farmers to navigate the challenges of climate change, promoting agricultural productivity and environmental sustainability in the dry zone of Sri Lanka.

IMPACT OF TEMPORAL CLIMATE VARIABILITY AND LAND USE DYNAMICS ON THE INTEGRITY OF SEAGRASS BEDS IN THE NEGOMBO ESTUARY, SRI LANKA

Wed, 20 Nov 2024 00:00:00 GMT

IMPACT OF TEMPORAL CLIMATE VARIABILITY AND LAND USE DYNAMICS ON THE INTEGRITY OF SEAGRASS BEDS IN THE NEGOMBO ESTUARY, SRI LANKA Wickma, R.A.T.; Chathurani, S.H.U.; Jayasundara, J.M.N.M.; Dahanayaka, D.D.G.L.; Egodawatta, W.C.P. Seagrasses are marine angiosperms, thriving in brackish and shallow marine waters. This study aimed to assess the impacts of rainfall changes due to climate anomalies and anthropogenic land use changes on the distribution, species richness and diversity of the seagrass beds in selected locations in the Negombo Estuary. Locations with abundant seagrass beds were randomly selected and surveyed from August to October 2024. Three transects perpendicular to the shoreline were established across four distinct ecozones. Water quality and seagrass beds were assessed to determine their current status compared to past changes in rainfall and land use within the estuarine ecosystem. The blue carbon stocks of seagrass ecosystems were also quantified by estimating the total above and below-ground organic carbon fractions of seagrass beds. The present status of the estuarine seagrass spatial distribution, species richness, and diversity were compared with the published literature. Over the past three decades, notable changes in monthly average rainfall were observed during the south west and second inter-monsoon periods. Land use changes during the past two decades exhibited an increase in vegetation (4.70%), built-up areas (4.24%), and roads (1.16%), while water areas decreased by 0.76%. Estuary sections near Basiyawaththa exhibited the highest diversity, while Kadolkele and Munnakkaraya recorded no diversity, being composed only of Halodule pinifolia. Quantified seagrass coverage of three sections Munnakkaraya, Kadolkele and Basiyawaththa were 77%, 74% and 65%, respectively. Seagrass coverage and density were significantly correlated to Secchi-depth, indicating an indirect link between turbidity, rainfall, and water influx. Sea surface temperature exhibited a negative correlation linking the adverse effect of elevated temperatures, likely caused by thermal stress. The blue carbon stock of the ecosystem was significantly higher at Munnakkaraya (24.15 Mg C ha⁻¹) compared to Kadolkele (14.35 Mg C ha⁻¹) and Basiyawaththa (13.45 Mg C ha⁻¹). This study underscores the sensitivity of the Negombo Estuary’s seagrass ecosystem to rainfall fluctuations, land-use changes, water quality variations, and blue carbon content.

IMPACT OF SEASONAL FLOODS ON THE GROWTH OF IMMATURE RUBBER PLANTS IN THE WET ZONE OF SRI LANKA

Wed, 20 Nov 2024 00:00:00 GMT

IMPACT OF SEASONAL FLOODS ON THE GROWTH OF IMMATURE RUBBER PLANTS IN THE WET ZONE OF SRI LANKA Mallawaarachchi, I.S.; Nakandala, S.A.; Warnasooriya, W.M.R.S.K.; Piyarathne, P.N.M.S.; Udayakumari, U.N. Seasonal floods, particularly during monsoons, present a major challenge to rubber cultivation, a key crop in the Sri Lankan economy. This study aimed to investigate the impact of seasonal floods on the morphological, physiological, and biochemical properties of immature rubber plants, and the soil properties. Immature, monoclonal (RRIC 121) rubber plantation at Mohomadi Estate in Agalawatta Plantation PLC, was selected, featuring rubber growing in flood-prone low-lying areas, and non-flooded higher terrain. Tree-by-tree variation of 150 trees each from flooded and non-flooded areas was examined for morphological, physiological, and biochemical properties along with soil analysis. The data were statistically analyzed using the T-test procedure in the SAS software. Two flood events were reported during the study period. Flood-affected plants exhibited significant (p<0.05) reductions in height, girth, and leaf number, recording a 30% decrease in growth and a 25% mortality rate (p<0.05). Further, a significant decline (p<0.05) in chlorophyll, and epicuticular wax content of rubber leaves was observed in flood-affected plants, while stomatal conductance and relative water content were significantly higher (p<0.05). Soil analysis indicated a significantly lower organic carbon, total nitrogen, C: N ratio, and cation exchange capacity in flooded areas, while bulk density and pH were significantly higher. The soil pH of the flooded and non-flooded areas was 5.55 and 5.23, respectively, with the flooded area slightly exceeding the optimal range of 4.5 5.5 for the Agalawatta soil series. The findings underscore the detrimental impact of seasonal floods on immature rubber, emphasizing the need for research on yield attributes, flood-tolerant clones, and effective mitigation strategies to sustain rubber plantations in the wet zone of Sri Lanka, where seasonal flooding is frequent.