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Nitrification Inhibition by Karanja (Pongamia glabra Vent) Seed Powder and Its Extract

2026-08-05T09:50:15Z

Title: Nitrification Inhibition by Karanja (Pongamia glabra Vent) Seed Powder and Its Extract Authors: Thurkka, S.; Kirisan, A.; Gnanavelrajah, N. Abstract: Nitrification inhibitors are applied to slow down the conversion of ammonium to nitrate, which will enhance nitrogen availability to crops, and nitrogen use efficiency in farming systems by reducing nitrogen losses. This study aimed to assess the nitrification inhibition potential of Karanja (Pongamia glabra Vent) seed powder and its extract. The experiment comprised three phases: incubation study, leachate study, and microbial study, with seven treatments -T1 (Soil), T2 (Soil + Urea), T3 (Soil + Urea + 5% Neem oil), T4 (Soil + Urea + 10% Karanja extract), T5 (Soil + Urea + 20% Karanja extract), T6 (Soil + Urea + 10% Karanja powder), and T7 (Soil + Urea + 20% Karanja powder). Baseline soil properties included pH 6.58, EC 67.73 μS/cm, CEC 67.36 cmol (+)/kg, phosphorus 12.46 ppm, potassium 228.07 ppm, and total nitrogen 0.023%. Karanja powder and Karanja extract contained 0.313% and 0.014% nitrogen, respectively. According to the incubation study the highest nitrification inhibition % was found in T3 (52.4%) followed by T5 (49.8) and T4 (46.2). Treatments T6 and T7 (Karanja powder) exhibited no significant inhibition. Leachate study showed a significant reduction in nitrate leaching loss in T3, T4 and T5 compared to T2, T6 and T7. Microbial analysis confirmed the inhibition by Karanja extract, supporting its role as an effective nitrification suppressor. The study concludes that Karanja extract and neem oil are potent natural nitrification inhibitors, while Karanja powder alone is ineffective in this regard. Further studies under field conditions are suggested to verify the results.

Effect of Mulching on Soil Physical Properties under Dry Zone Condition: Evidence from Knol-khol (Brassica oleracea var. gongylodes) Cultivation in Kilinochchi, Sri Lanka

2026-08-05T09:40:08Z

Title: Effect of Mulching on Soil Physical Properties under Dry Zone Condition: Evidence from Knol-khol (Brassica oleracea var. gongylodes) Cultivation in Kilinochchi, Sri Lanka Authors: Methmal, T.G.S.; Sellathurai, T.; Sritharan, S. Abstract: Soil physical degradation and rapid moisture loss are major constraints to vegetable production in the dry zone of Sri Lanka. Although mulching is widely used to conserve soil moisture, information on its effects on soil physical properties under local conditions is limited. This study evaluated the impact of different mulching materials on soil moisture storage, soil temperature, bulk density, and soil organic matter during Knol-khol (Brassica oleracea var. gongylodes) cultivation in Kilinochchi District, Sri Lanka. A field experiment was conducted using a Randomized Complete Block Design (RCBD) with four treatments: paddy straw mulch, palmyra dry leaves mulch, polythene mulch, and a no-mulch control, each with three replicates. Organic mulches were applied at a thickness of 15 cm one week before transplanting. Soil moisture storage, soil temperature, bulk density, and soil organic matter were measured throughout the cropping period using standard field and laboratory methods. Data were analyzed using analysis of variance (ANOVA), and treatment means were compared using Dunnett’s test at a 95% confidence level (p ≤ 0.05). Mulching significantly improved soil physical properties. Mean soil moisture storage was highest under palmyra dry leaves mulch (23.8 ± 1.9%), followed by paddy straw (21.6 ± 1.7%), polythene mulch (20.2 ± 1.5%), and the control (17.4 ± 1.6%). Organic mulches also moderated soil temperature, recording lower values under palmyra dry leaves (27.1 ± 0.8 °C) and paddy straw (27.8 ± 0.9 °C) than under polythene mulch (29.4 ± 1.0 °C) and the control (30.2 ± 1.2 °C). Bulk density was lowest under palmyra dry leaves (1.42 ± 0.05 g cm⁻³), while soil organic matter increased to 1.26 ± 0.08% compared with 1.02 ± 0.05% in the control. The results demonstrate that organic mulching, particularly palmyra dry leaves, is an effective and sustainable option for improving soil physical conditions, conserving moisture, and supporting Knol-khol cultivation in dry-zone environments.

An Attempt to Develop High-performance Edible Mushroom Hybrids through a Cross-Breeding-Based Approach

2026-08-05T09:34:42Z

Title: An Attempt to Develop High-performance Edible Mushroom Hybrids through a Cross-Breeding-Based Approach Authors: Husnil Rila, M.N.; Shyamalee, H.A.P.A.; Weerasinghe, G.Y.H.; Niroshani, S.A.M.; Saththivel, P. Abstract: Oyster mushrooms (Pleurotus spp) are highly valued edible fungi, accounting for 25% of global mushroom production, and are rich in protein (15-30% dry weight), essential vitamins, minerals, and dietary fiber. However, commercial cultivation faces challenges, including low biological efficiency, slow growth, and environmental sensitivity, necessitating the development of improved strains through systematic breeding approaches. This study examined six interspecific hybrid combinations among six oyster mushroom types: Pleurotus ostreatus (American Oyster), P. cystidiosus (Abalone), P. djamor (Pink Oyster), P. pulmonarius (Black Oyster), P. sajorcaju (Bhutan Oyster), and P. ostreatus var. curly (Curly Oyster) to identify superior hybrids for commercial-scale production. The experiment was conducted at the Agriculture Research Station, Thelijjawila, Matara, Sri Lanka, using a Completely Randomized Design (CRD) with 15 replicates per treatment. A total of six hybrid combinations were developed: Bhutan × American Oyster (T1), Bhutan × Abalone (T2), American Oyster × Curly (T3), Pink Oyster × Curly (T4), American Oyster × Black Oyster (T5), and Abalone × Black Oyster (T6). Clamp connection microscopic observation confirmed successful dikaryon formation. Marked variations (P < 0.001) were noted among treatments regarding spawn run duration, fruiting initiation, yield, stalk length, and cap diameter. T3 and T4 showed exceptional performance, attaining the shortest spawn run (~26 days), the earliest fruiting (16-28 days), and the greatest yields (83.71 g and 71.29 g), respectively. Performance variation was significant, with 84% range for spawn run time, 369% for fruiting start, and 187% for yield. Heritability study revealed that a substantial genetic regulation of stalk length (R² = 85.34%) and modest effect on yield (R² ≈ 60%), whereas cap diameter was predominantly influenced by environmental factors (R² = 36.96%). T3 and T4 are endorsed for commercial use owing to their enhanced productivity, swift growth, and reliability. The findings confirmed that interspecific hybridization is an effective breeding strategy for developing Pleurotus cultivars with enhanced biological efficiency and improved cultivation potential.

Eusocial Structure of Macrotermes Termites and Antagonistic Potential of Fungal Biocontrol Agents against Termitomyces Fungus and Termites

2026-08-05T09:28:05Z

Title: Eusocial Structure of Macrotermes Termites and Antagonistic Potential of Fungal Biocontrol Agents against Termitomyces Fungus and Termites Authors: Kugatharshini, S.; Sritharan, S.; Jegathambigai, V.; Mikunthan, G. Abstract: The study was conducted to investigate the mutual relationship between Macrotermes termites and their symbiotic fungus Termitomyces, focusing on their structural organization and functional roles within the mound ecosystem. Additionally, the research explored the potential of using fungal antagonists as eco-friendly biocontrol agents for sustainable termite management. Field observations were conducted on ten Macrotermes mounds and detailed data were collected from only one representative mound, which was dome-shaped with multiple ventilation holes measuring 3–6 cm in diameter, an average height of 120 cm, and an average width of 190 cm. Internal examination revealed well-organized chambers containing fungus combs with a mean fresh weight of 230.47 ± 92 g, a perimeter of 37.5 ± 5 cm, and a volume of 1793.1 ± 926 cm³, indicating advanced eusocial organization and efficient resource allocation. The isolated Termitomyces species displayed white, cottony mycelial growth with basidiomycete characteristics, including clamp connections observed microscopically. Dual culture assays with three replicates demonstrated strong antagonistic activity of Trichoderma viride against Termitomyces, achieving 83.33% inhibition of mycelial growth after 14 days. An eco-friendly substrate formulation containing tamarind seed and fenugreek seed supported maximum mycelial growth and sporulation (6.23 ± 0.3 × 10⁶ spores g⁻¹) at an optimal pH range of 5.5–6.5. T. viride colonized sterilized termite combs more effectively than wild combs, suggesting that native microbial flora restricted colonization. Laboratory bioassays revealed a significant effect (p < 0.05) of entomopathogenic fungi on termite mortality, with Paecilomyces cerevisiae causing the highest mortality (85%), followed by Metarhizium anisopliae (75%) and Beauveria bassiana (49.3%). Overall, the findings support the use of fungal-based biocontrol agents in environmentally sustainable management of Macrotermes termites.