Evaluation of Aging Methods on the Surface Characteristics of Hydrochar and Germination Indices for Kale Seeds

Hydrochar derived from hydrothermal carbonization (HTC) has been recognized as a potential absorbent and horticultural substrate. However, its practical application limited due to low adsorption capacity negative effects on plant growth. To address these issues, three pre-treatment methods (water washing, microbial aging, freezing-thawing aging) were employed further improve the physical structure chemical properties of hydrochar. A seed germination test with kale (Brassica oleracea var. acephala D.C) was conducted evaluate phytotoxicity modified hydrochars. The results showed that aging considerably enhanced physicochemical Specifically, under bulk density microbial-aged hydrochar (MHC) decreased by 8.1%, porosity increased 24.8%, water-holding 36.54% compared fresh (FHC). Moreover, surfaces MHC aged (FTHC) observed rough cracked macro pore structures. Fourier transform infrared (FTIR) spectroscopy revealed functional group’s intensities four materials varied, FTHC had more oxygen-containing groups than others. Additionally, surface areas 318.64% 238.98% FHC, respectively. indicated strong inhibitory effect while significantly (p < 0.05) improved rate root development. These findings suggest among different methods, demonstrated greatest for in improving promoting germination. This study opens up new avenues research suggests future studies should focus optimizing process.