Biochar impact on tensile strength of Dystric Cambisol aggregates – a model study

Aggregate tensile strength is a significant parameter of soil structure. Adequate mechanical stability of aggregates promotes long-term crop productivity due to, inter alia, maintaining gas diffusion, facilitating root penetration and improving water infiltration. Soil aggregates characterized by high tensile strength are also resistant to erosion. Nowadays, intensive agriculture and environmental pollution contribute to clear deterioration of soil condition. The soil structure is often destroyed. In order to limit the negative phenomena, various soil additives are used, e.g. biochar.

In this paper, the effect of wood waste biochar on tensile strength and porosity of Dystric Cambisol artificial aggregates was examined. The experiments were performed on dry-air and wet soil aggregates non-containing and containing 0.1% or 5% dose of biochar. Tensile strength of the probes was determined using strength testing device (Zwick/Roell), whereas porosity – by mercury intrusion porosimetry (Micrometrics). The obtained results indicated that the biochar addition decreases tensile strength of all examined aggregates. This effect was more significant for higher biochar dose – 5%. This phenomenon is probably connected with formation of macropores of larger sizes within aggregates after the biochar addition.

Research was conducted under the project "Water in soil - satellite monitoring and improving the retention using biochar" no. BIOSTRATEG3/345940/7/NCBR/2017 which was financed by Polish National Centre for Research and Development in the framework of "Environment, agriculture and forestry" - BIOSTRATEG strategic R&D programme.