Scholarly Publications

Effects of Different Plant and Residue-Derived Ashes on Ameliorating Soil Acidity in Paddy Soils of the Low Country Wet Zone, Sri Lanka.

2026-08-14T10:24:37Z

Effects of Different Plant and Residue-Derived Ashes on Ameliorating Soil Acidity in Paddy Soils of the Low Country Wet Zone, Sri Lanka. Maheshani, H.H.G.P.; Rupasinghe, M.G.N.; Amarasinghe, S.R. Soil acidity is a major constraint limiting paddy productivity in the Low Country Wet Zone (LCWZ) of Sri Lanka, while the high cost and limited availability of conventional liming materials such as dolomite restrict their use among farmers. Although wood ash has long been recognized as a liming agent, comparative information on the effectiveness of locally available plant and residue-derived ashes compared with dolomite remains limited. Therefore, this study aimed to evaluate the comparative liming effect of different ash sources. An eight-week laboratory incubation experiment was conducted using acidic paddy soil collected from the Regional Rice Research and Development Centre, Bombuwela, Sri Lanka. Treatments were arranged in a Completely Randomized Design with four replicates. Ashes (2 t ha-1) derived from rubber (Hevea brasiliensis), cinnamon (Cinnamomum verum), alstonia (Alstonia macrophylla), and rice husk (Oryza sativa residue) were applied, along with dolomite and an unamended control, with recommended rates of N, P, and K fertilizers (urea – 40 kg/ac, MOP – 44 kg/ac, TSP – 20 kg/ac, respectively) as per Department of Agriculture guidelines. The ashes were produced under open combustion conditions, with recorded pH ranging from 9.5 to 12.9. Soil moisture was maintained at 50% of field capacity, and weekly measurements of pH, EC, available P, exchangeable K, and organic matter (OM) were conducted. All ash treatments significantly (p < 0.05) increased soil pH compared to the control, while cinnamon ash exhibited the highest liming efficiency in week 2, raising soil pH from 4.65 to 6.0. However, dolomite-treated soil showed significantly (p<0.05) higher pH (5.67) in week 8. Cinnamon ash-amended treatment increased available P (from 4.4 to 17.56 ppm) and exchangeable K (from 17.93 to 258.48 ppm) by week 8. EC values increased in all treatments, with significantly (p<0.05) highest EC (278.25 μ S/cm) observed in cinnamon ash-treated soil. Organic matter content improved significantly (p<0.05) in rubber (8.8%) and alstonia (8.2%) amended treatments compared to the control. The findings suggest that using locally available cinnamon wood ash could provide an affordable and sustainable alternative to dolomite for ameliorating acidic soils in the LCWZ. Field-scale validation is recommended prior to widespread agricultural adoption.

Carbon Dioxide Emissions from Model Soil Aggregates Incorporated with Organic Amendments: Effects of Organic Matter and Water Repellency.

2026-08-14T10:12:30Z

Carbon Dioxide Emissions from Model Soil Aggregates Incorporated with Organic Amendments: Effects of Organic Matter and Water Repellency. Liyanage, T.D.P.; Leelamanie, D.A.L.; Lekamge, T.L.S.P. Model soil aggregates incorporated with organic amendments (OAs) can serve as nutrient-rich potting media. The OAs can induce water repellency (WR) in model soil aggregates restricting moisture availability for the organic matter (OM) decomposition. Decomposition of OM can reduce carbon dioxide (CO2) emissions temporally due to limited substrate availability to the microorganisms. On the other hand, the decomposition loss of OM can reduce WR, which in turn increases CO2 emissions. However, the net effects of these OM and WR variations on CO2 emissions are still unclear. This study explored CO2 emissions from OAs-incorporated model soil aggregates considering the effects of OM and WR. Surface Ultisol soil from Mapalana, Sri Lanka, was amended with 5 types of air-dried and/or ground OAs (mahogany and casuarina litter at an early decomposition stage, goat and cattle manure less than one week old, compost) at 15% (w/w) rate. Using these samples, uniform model aggregates (1×1×0.5 cm) were prepared and kept under laboratory conditions for over 15 weeks, maintaining initial air-dried moisture contents. Weekly, CO2 emissions (trapping by NaOH), WR at the same initial moisture contents (persistence; water drop penetration time, degree; sessile drop contact angles), and OM% (Walkley-Black and Loss on Ignition methods) were measured. Both OM% and WR decreased temporally due to decomposition. The CO2 emissions consistently decreased within the first three weeks (initial stage) and then (later stage) showed emission pulses on certain days. According to ANOVA, the effects of OM% on CO2 emissions were statistically significant (p<0.05) during the initial stage. In the later stage, the statistically significant (p<0.05), non-linear, negative correlation between CO2 emission pulses and the corresponding contact angles indicated that decreasing WR improved water penetration and microbial access, thereby increasing CO2 emissions. The interaction effects between the OM% and the degree of WR on CO2 emission pulses were significant (p<0.05) in addition to their individual effects in this stage. Overall, the initial CO2 emissions from OAs-incorporated model soil aggregates were regulated by OM%, while the latter were influenced by both OM% and WR.

Effect of Storage Conditions on Staphylococcus aureus Found in Giant Freshwater Prawn.

2026-08-14T10:08:45Z

Effect of Storage Conditions on Staphylococcus aureus Found in Giant Freshwater Prawn. Kuragodage, A.U.; Deepananda, K.H.M.A.; Peiris, H.H.; Jayasinghe, U.A.D.; Jones, C. Ensuring microbial safety of the commercially important giant freshwater prawn (GFP), Macrobrachium rosenbergii, is crucial given its rising commercial value and sensitivity to postharvest handling conditions. Staphylococcus aureus is a major foodborne pathogen of concern in crustaceans; however, its behaviour under different storage conditions remains poorly understood. This study examined the growth of naturally contaminated S. aureus on GFP stored under three standard postharvest methods. A total of 72 fresh male prawns (average weight, 440 ± 38 g; length, 30 ± 4 cm) from the Ridiyagama Reservoir, Sri Lanka, were transported under chilled conditions and randomly assigned to three treatments (n=24 per treatment): (i) ice storage (1:1, w/w), (ii) freezing at −20◦C, and (iii) blast freezing at −35◦C followed by storage at −20 ◦C. Microbiological counts were performed at three-day intervals from day 0 to day 21, following ISO standard procedures, with analyses performed in triplicate at each time point. The initial (day 0) S. aureus count in GFP was 269 ± 63 CFU/g. S. aureus showed significantly different survival patterns (p<0.05) across the three storage methods. Ice-stored samples exhibited continuous and substantial growth, reaching a 3,977 ± 440% increase by day 21, with three distinct proliferation phases: a gradual increase during days 0–9 (83 ± 19%), a moderate rise from days 9–15 (575 ± 76%), and a sharp escalation during days 15–21, resulting in a net increase of 3,402% in the final phase. Conversely, freezing at −20◦C led to a gradual decline in S. aureus counts (56 ± 4% of initial levels by day 21), whereas blast-freezing resulted in the greatest reduction, with counts at 28 ± 5% of the initial level. Prawns stored on ice exceeded international microbial limits after day 12, whereas both frozen treatments remained within regulatory limits established by the European Union (EU), Asian, and Oceania standards throughout the storage period. These results indicate that ice storage promotes S. aureus growth due to favourable conditions, whereas freezing, particularly blast freezing, decreases the pathogen’s persistence. Rapid freezing thus provides superior microbial safety for GFP and should be prioritised in postharvest handling systems to uphold product quality and compliance with international standards.

Development of a Small-Scale Extruder Machine and Evaluation with the Production of Jackfruit Seed Flour-Based Extruded Snack.

2026-08-14T10:05:02Z

Development of a Small-Scale Extruder Machine and Evaluation with the Production of Jackfruit Seed Flour-Based Extruded Snack. Wijesinghe, S.M.M.; Rajawatta, K.M.W.; Wijayasekara, K.N. The development of small-scale extruder machines has become increasingly important due to the growing demand for efficient food processing technologies. This study focuses on the design and fabrication of a screw-type extruder machine and the assessment of its performance using jackfruit seed flour as the primary raw material for the production of extruded snacks. Among existing designs, screwtype mechanisms were chosen over piston-type mechanisms due to their simpler operation and continuous processing capability. The fabricated machine consists of essential components, comprising the feeder, barrel, screw, heating system, and die, all mounted on a single integrated frame. The performance of the machine was evaluated at different moisture contents, while the quality of the extruded snacks assessed through physicochemical and sensory analysis. Quality parameters measured as expansion ratio, density, water absorption, and water solubility index. Results showed that for the density, expansion ratio, Water Absorption Index (WAI), and Water Solubility Index (WSI) were 1.11± 0.08 g cm-3, 1.33 ± 0.02%, 3.58 ± 0.04 g g-1, and 22.85 ± 0.07% respectively. Regression analysis revealed that the temperature had the statistically significant effect on the expansion ratio (P < 0.001). Sensory evaluations were carried out for two treatments by a panel comprising 30 untrained panelists. According to the Friedman nonparametric test, sensory evaluation results for treatment two has the highest preference in terms of color (4.50), aroma (4.25), texture (4.50), flavor (4.50), mouthfeel (4.50), appearance (4.50) and overall acceptability (4.50). In treatment number two, the formulation was composed of 30 g jackfruit seed flour, 49 g wheat flour, 20 g powdered sugar, and 1 g salt. Commercially imported extruders normally cost more than LKR 100,000, whereas the estimated total cost of the small-scale extruder was approximately LKR 13,000. The study concludes by recommending future research on incorporating a vacuum chamber within the barrel to further enhance product quality.