BOOK OF ABSTRACTS 135 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Thursday, 27 August 2026 / Hall C Soil Organic Matter, Caustobiolites, and Biochar SL65 Organic Components of Biochar/Hydrochar act as Chemical Messengers that Can Reshape Microbiome Composition and Influence Plant Growth Response Heike Knicker1,*, Francisco J. Moreno-Racero1, Álvaro F. Garcia-Rodriguez1, Jorge Medina2, Laura J. González2, Humberto Aponte2, Miguel A. Rosales3 1 Group of Interactions between Soils, Plants and Microorganisms, Department of Food Biotechnology, Instituto de la Grasa (IG-CSIC), Building 46, UPO Campus, Ctra. de Utrera km 1, 41013 Seville, Spain 2 Laboratory of Soil Microbial Ecology and Biogeochemistry, Institute of Agrifood, Animal and Environmental Sciences (ICA3), Universidad de O Higgins, Campus Colchagua, Chile 3 Depart. Stress, Development and Signaling in Plants, Estación Experimental del Zaidín (EEZ-CSIC), Granada, Spain. * Corresponding author: heknicker@ig.csic.es Over the last decades Biochar (BC) and Hydrochar (HC) have become the subject of intense scientific study, due to its positive effects on crop production. However, much of the existing literature focuses on demonstrating beneficial outcomes rather than elucidating the “why and how”. Indeed, our understanding of the processes activated after BC/HC incorporation into soils remains limited and is largely attributed to changes in soil chemical and physical properties. Recent results from our group, performing pot experiments cultivating lettuce (Lactuca sativa L. var. Batavia) under semi hydroponic conditions on BC (vineyard prunnings)/peat substrates suggest that BC can directly affect the internal nitrogen (N) use efficiency of plants [1]. Whereas previous studies related such effects mainly to N retention via sorption to BC surfaces, our results demonstrate that, in addition, BC stimulates the plant’s internal N-cycle by enhancing the activity of key enzymes involved in NO3⁻ and NH4⁺ assimilation. This metabolic enhancement contributes to more efficient use of available N and greater protein accumulation in shoot tissues, even under reduced total N concentrations. These findings offer promising perspectives for optimizing BC-based fertilizers, not just as passive N-retaining agents, but as enhancers of physiological N metabolism [2]. In further experiments, HC of chicken manure and its respective humic acid (HA) were added to a Cambisol and incubated for 77 days in a greenhouse (25 °C) under well-irrigated (WI) and water deficiency (WD) conditions. Soil microbial functioning was assessed using MicroResp to determine basal respiration (BR), together with fluorescein diacetate (FDA) hydrolysis, arylsulfatase, arginine ammonification, urease, and phenol oxidase activities. HS
RkJQdWJsaXNoZXIy NDA4Mjc=