BOOK OF ABSTRACTS 265 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Technologies and Applications P5.6 WEOM Extraction Efficiency and Selected Optical Properties of Soils Amended with Microbiologically Enriched Biochar Kamil Skic1, Patrycja Boguta1, Angelika Gryta1, Agata Gryta1, Magdalena Frąc1 1 Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4 Str., 20-290 Lublin, Poland, email: k.skic@ipan.lublin.pl Biochar enriched with beneficial microorganisms represents a promising strategy for increasing soil organic matter pool as well as improving soil fertility and biological activity. On the one hand, the high carbon content, high porosity, and well-developed specific surface area of biochar may promote the growth and activity of microorganisms [1]. On the other hand, the introduction of biochar together with microorganisms may affect the composition of soil organic matter through the modification of humification processes, stimulation of microbial activity, and transformation of labile organic carbon fractions [2]. Therefore, in order to properly assess the agronomic and environmental benefits resulting from the application of microbiologically enriched biochar, it is necessary to understand its impact on the quantity and quality of soil organic matter. The aim of this study was to determine the effect of biochar inoculated with the strain Trichoderma atroviride G79/11, obtained from the collection of the Laboratory of Molecular and Environmental Microbiology (IA PAS, Lublin, Poland), on extraction efficiency and selected optical parameters of water-extractable organic matter (WEOM). Biochar was produced from digestate derived from an agricultural biogas plant at pyrolysis temperatures of 300°C, 450°C, and 600°C. The material was then inoculated with spores of Trichoderma atroviride G79/11 (5.04 × 10^8 CFU/g) and introduced into soils at concentrations of 0.5%, 1%, 3%, and 5%. The amended soils were incubated for 14 days at 23°C. The WEOM content was determined by extracting soil samples with ultrapure water for 2 hours. After sediment separation, the WEOM was dried and weighed. The solutions were also analyzed spectrophotometrically to evaluate the optical parameters (E4/6, E2/3, E2/6) of the isolated organic matter. The obtained results showed that WEOM extraction efficiency generally increased with increasing biochar dose. Higher extraction efficiency was observed for biochar produced at lower pyrolysis temperature, suggesting the presence of more labile and readily available carbon forms that may stimulate microbial activity. The greatest changes in optical parameters were observed for BC300 biochar, whereas BC600 caused relatively minor modifications of WEOM. The introduction of biochar produced at lower pyrolysis temperatures increased
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