Impact of Biochar on Hydraulic Properties of Sandy Calcareous Soil: Influence of Particle Size and Application Depth.

A laboratory column experiment was conducted to investigate the effects of biochar with different particle sizes and application depths on hydro-physical properties of sandy soil including: soil water penetrability, infiltration rate, intermittent evaporation, water retention and saturated hydraulic conductivity. Biochar produced from conocarpus wastes was applied in different sizes (< 0.5 mm (S₁), 0.5-1mm (S₂) and 1-2 mm (S₃)) as biochar-soil mixture layer 2-cm thick at three application depths of 0 cm depth (D₀), 5 cm depth (D₅) and 10 cm depth (D₁₀). The results indicated that applying biochar restricted the movement of water penetrability as a result of decreasing the waterfront and saturated hydraulic conductivity. Additionally, the cumulative evaporation was the highest and amounted to 40.92 mm in the non-treated soil, but it recorded the lowest amount of 32.25-35.46 mm in the biochar-treated soil (especially at the application depth of D₀). Among different particle size of biochar, no significant differences of the cumulative evaporation were observed. The biochar addition caused significant increases in the amount of conserved and retained water compared to control soil. The highest amount of water conserved in soil was pronounced for S₂biochar at D₅.In addition, the cumulative water infiltration through the soil was significantly reduced by S₁ and S₂ biochar when applied at D₀.The values of saturated hydraulic conductivity for the biochar treatments were significantly lower than those for the control, with the lowest values for S₁ at D₀ and D₅. It could be concluded that applying finer particles (˂ 1 mm) of biochar may be more effective to improve some hydro-properties of coarse-textured soils.