| Abstract |
Marine biomass has gained attention as a sustainable feedstock for biochar, but its
high salt content limits its agricultural application. This study investigated the watersoaking
pre-treatment of Laminaria pallida and Gracilariopsis funicularis to reduce
salinity and improve biochar quality for agricultural applications. The experiment
included three factors: water temperature (25 °C and 100 °C), soaking duration (0, 0.5,
2, and 6 h), and seaweed species, resulting in 16 treatment combinations. Significant
effects (P < 0.05) of soaking conditions were observed on biochar pH, electrical
conductivity (EC), macronutrient concentrations (C, N, P), cations (Na, K, Ca, Mg),
and heavy metals. Cold-water soaking of G. funicularis for 6 h produced the most
favorable biochar, with a reduced sodium concentration (from 23.9 g/kg to 12.2 g/
kg), lower EC (29.3 mS/cm), moderate pH (8.6), and high nutrient content (N: 5.17%;
P: 127 mg/kg). In contrast, L. pallida biochar retained higher sodium (46.5 g/kg to
62.6 g/kg) and strong alkalinity (pH 11.3), limiting its agronomic suitability. Hot water
soaking reduced N and P but increased Zn concentrations (up to 5.5 mg/kg and
9.52 mg/kg in L. pallida and G. funicularis, respectfully), indicating trade-offs between
nutrient retention and metal enrichment. Importantly, all heavy metals measured (Cd,
Cr, Cu, Ni, and Zn) remained below permissible limits for organic soil amendments.
Unlike previous studies, the current study systematically optimised a simple, lowcost
pre-treatment that reduces salinity while preserving nutrient value in marine
biomass-based biochar. These findings demonstrate that, compared to L. pallida, pretreated
G. funicularis biochar has strong potential as an eco-friendly soil amendment
in arid regions, where salinity management and nutrient efficiency are critical.
Future studies should integrate this approach with vermicomposting or microbial
inoculation to further leach excess cations and stabilise biochar quality. |
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