Impact of wood-derived biochar on the hydraulic characteristics of compacted soils: Its influence on simulated farmland carbon sequestration

*Corresponding author e-mail: Ahmed.ahmed@mail.mcgill.ca A b s t r a c t. The addition of biochar is often proposed to increase agricultural soil quality and crop yield, while at the same time sequestering carbon from the atmosphere to help mitigate global climate change. In this research, the pore-size distribution, and saturated hydraulic conductivity of sandy loam and clay loam soils amended with varying dosages (0-10% dry basis) and two different particle sizes (0.5-420 μm (PS1) or 421-841 μm (PS2)) of wood-derived biochar were investigated under compacted conditions (5, 10, or 15 standard Proctor rammer blows (5B, 10B, or 15B, respectively)). In the 5B compacted SL (SL-5B) soil, the volume of the soil fissures and transmission pores decreased, while the volume of the storage pores (SP) increased with increasing wood-derived biochar dosage. 23.1±0.9% of the volume of the 5B compacted clay loam (CL-5B) are storage pores, this value increased to 27.4±2.0% upon amendment with 10% PS1. The saturated hydraulic conductivity of the sandy loam-5B soil amended with 10% PS1 decreased from 6.8±0.3 to 0.80±0.03 mm h. The sandy loam farmland C emissions decreased by 0.071 tC ha y, whereas CL farmland C emissions decreased by 0.091 tC ha y. K e y w o r d s: soil biochar mixture, water retention, pore-size distribution, hydraulic conductivity, carbon sequestration