Wood gasification biochar enhances soil carbon sequestration without affecting greenhouse gas fluxes or wheat yield in sub-alkaline soil

The agricultural sector plays a vital role in mitigating soil greenhouse gas (GHG) emissions and enhancing carbon sequestration. One promising approach is wood biochar produced through gasification, which generates both syngas and stable biochar. This study evaluates the effects of wood gasification biochar (WGB) on subalkaline soil under Mediterranean climate conditions. A field experiment was conducted over two cropping years, monitoring soil N2O, CH4, and CO2 fluxes, along with temperature and water content, for two treatments: unamended wheat (control) and wheat amended with 60 Mg ha−1 of WGB. Additionally, soil physicochemical properties at 0–10 cm and 10–40 cm depths and wheat yield were assessed. In the WGB treatment, soil N2O, CH4, and CO2 fluxes remained unchanged, though a slight increase in soil temperature (+0.1 °C) was observed. No significant differences were detected in soil pH, total and ammoniacal nitrogen, bulk density, or cation exchange capacity. However, soil nitric nitrogen levels significantly decreased. Soil carbon stock increased 2.2-fold at 0–10 cm and 1.4-fold at 10–40 cm, with this effect persisting into the second year. Wheat yield remained comparable between treatments, averaging ∼2.0 Mg ha−1 (control) vs. ∼1.8 Mg ha−1 (WGB) in year one and ∼3.9 Mg ha−1 vs. ∼3.1 Mg ha−1 in year two. These findings indicate that wood gasification biochar enhances soil carbon sequestration without affecting GHG emissions or wheat yield, reinforcing its potential for sustainable soil management and circular agriculture