| Abstract |
The agronomic utilisation of marine-derived biochar and its vermicompost in soilless horticulture remains insufficiently understood. This study evaluated the potential of desalinated marine-biomass-derived biochar and its vermicompost to enhance tomato seedling establishment and vegetative growth in soilless media. In Study 1, Laminaria pallida and Gracilariopsis funicularis were soaked in cold and hot water for varying durations to reduce salinity before pyrolysis. Cold water soaking of G. funicularis for 6 h produced the most favourable biochar, characterised by reduced Na (12.2 g/kg), moderate pH (8.6), lower EC (29.3 mS/cm), and heavy metals levels below permissible limits, indicating effective salt reduction without excessive alkalinity. In contrast, L. pallida biochar had higher Na (30.22–62.6 g/kg) and pH (10.98–11.35). Study 2 evaluated cattle-manure vermicompost amended with 0–9% of the optimised biochar. The 9% rate produced the most suitable amendment, with a low C/N ratio (11.43), moderate EC (2.63 mS/cm), reduced Na (3.44 g/kg), improved germination indices in all vegetables except cabbage, and heavy metals below permissible limits. In contrast, 0% biochar vermicompost showed higher pH (8.21), C/N (17.60), and NO₃/NO₂-N (54.34 mg/kg). Study 3 evaluated replacing coco peat with optimised biochar-amended vermicompost for tomato seedling establishment (with/without ammonium sulfate) and vegetative growth (with fertilizer). Seedlings in 100% vermicompost with fertilizer achieved the highest height (13.6 cm) and leaf area (49.45 cm²), whereas 100% vermicompost without fertilizer resulted in poor growth. During vegetative growth, 100% vermicompost produced healthy plants with the highest chlorophyll content (31.67 SPAD), suggesting improved nutrient availability and substrate functionality. Overall, cold water soaking for 6 h enhanced biochar suitability, 9% biochar optimised vermicompost quality, and 100% vermicompost effectively supported tomato growth under fertilised conditions. |
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