Biochar as an amendment material for improvement of expansive soil properties in Central Asia

Soil salinity in Central Asia negatively impacts soil structure, leading to degradation and reduced water infiltration. This not only hampers agricultural productivity but also makes the land less suitable for construction due to its high susceptibility to deformation. Environmentally friendly materials like biochar, a carbon-rich substance, show promise in reducing the deformation of saline soils. However, the mechanisms behind its effectiveness are not yet fully understood. This study aims to analyse saline clays’ dispersion and sedimentation behaviour under varying pore water salinity levels (0 % to 10%). A biochar content of 5 % was selected as it is found to be optimum for plant growth and erosion resistance. It was found from the study that the biochar increases the aggregation of soil particles and enhances flocculation, improving soil dispersion characteristics. Biochar facilitates soil particle aggregation by increasing the cation exchange capacity. At higher pore water salinity levels (5% and 10%), the sedimentation behaviour of biochar-treated soil particles deviates from expectations, showing slower sedimentation rates and lower sedimentation heights. This is because the sodium ions are adsorbed by biochar, reducing salt’s effect on dispersion and sedimentation. The results demonstrate that biochar effectively enhances the stability of saline soils and, hence, has a potential use for ground improvement in the Central Asian region.