Influence of biochar on soil and compost properties

Recep Serdar Kara, MSc

Disertační práce

Abstract:

This study initially presented the diverse roles of biochar in soil systems, emphasizing how soil properties, biochar characteristics, and both environmental and experimental conditions shape its effects. To provide a comprehensive understanding, previously established mechanisms were examined, and biochar’s interactions within various contexts were assessed. Three main research aspects were investigated: (i) commercial biochar as a compost additive in agricultural soils, (ii) biochar and moisture sensor performance, and (iii) biochar in the remediation of contaminated soils. The first study examined wood-based biochar (Fagus sylvatica) as a compost additive and a tool for modifying the short-term outcomes of conventional compost applications, either through fresh additions or after different microbial activation methods. Treatment-specific effects on soil physicochemical, hydrophysical, and biological properties were observed, as well as on nutrient availability and the resulting plant responses. The findings showed strong associations between inherent soil properties, organic matter decomposition processes, organic carbon stability, and fractionation, which collectively influenced treatment outcomes. For instance, in a silt loam Luvisol under greenhouse conditions, fresh and Bokashi-fermented biochar significantly improved saturated hydraulic conductivity compared to sole compost and its application to Azotobacter-inoculated soils. On the other hand, with a lower rate of biochar addition, this metric was not significantly influenced in a Cambisol under field conditions. However, it strongly correlated with hygroscopic moisture-binding abilities and specific surface area modifications. A mechanistic approach was applied to investigate these modifications, particularly focusing on `active` permanganate-oxidizable carbon, which served as an important indicator of modified soil properties and functions within the available data. The second study evaluated the performance of commonly used frequency domain reflectometry (FDR) soil moisture sensors in organically-amended soils in a laboratory setting. Measurements on soils with varying organic carbon compositions revealed that recent biochar and compost applications may induce contrasting effects on sensor readings, leading to overestimation and underestimation, respectively. The findings indicated the necessity for a secondary, soil-specific calibration when utilizing FDR sensors in high-dose biochar- or compost-treated soils. The third remediation-focused study involved producing, characterizing, and applying an industrial waste-derived deinking paper sludge (DPS) biochar for cadmium remediation in artificially contaminated and aged soils of different textures. The results revealed significant reductions in cadmium bioavailability after incubation with DPS biochar. This outcome was particularly evident in coarser, highly contaminated soils, accompanied by increased enzymatic activity and mitigated plant stress. Overall, this study emphasized the multifunctionality of biochar in agricultural and environmental applications while also addressing its limitations. It provided critical insights into the interactions between carbon fractions and soil properties and presented direct, practical implications for soil management, sensor technology, and environmental remediation.

Keywords

hydrophysical properties, soil macronutrients, soil respiration, organic carbon fractions, active carbon, soil moisture sensor, cadmium remediation

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 3. 3. 2025

Obhajoba závěrečné práce

• Vedoucí: prof. Ing. Svatopluk Matula, CSc.
• Oponent: Radim Vácha, externi, Václav Kuráž, externi, Petr Fučík, Ing., externi

Česká zemědělská univerzita v Praze

Fakulta agrobiologie, potravinových a přírodních zdrojů

Doktorský studijní program:
Exploitation and Conservation of Natural Resources