Combining Biochar, Nitrogen Fertilizer and No-Tillage to Reduce Greenhouse Gas Emissions and Increase Rice Yield in Rainfed Lowland

No-tillage and biochar amendment are widely regarded as effective strategies to mitigate greenhouse gas (GHG) emissions. However, the combined effects of no-tillage, biochar and nitrogen (N) fertilizer application on rice yield and GHG emissions remain scarcely investigated. We conducted a two-year field experiment in central Cote d'Ivoire to assess how biochar and N-fertilizer application under no-tillage influences methane (CH4) and nitrous oxide (N2O) emissions, global warming potential (GWP), GHG intensity (GHGI), and rainfed lowland rice yield. The experiment included three N-fertilizer rates (0, 60, and 120 kg N ha-1) combined with two biochar rates (3, and 6 t ha-1) under no-tillage, alongside two additional treatments; N-only fertilizer (120 kg N ha-1) under no-tillage, and under manual tillage (conventional practice). No-tillage combined with biochar and N-fertilizer increased N2O emissions (9-96 %), but reduced CH4 emissions (13-21 %) and increased rice yields (4-10 %) compared to conventional practice. This trade-off led to significant reductions in GWP (10-20 %) and GHGI (15-18) by no-tillage combined with biochar and N-fertilizer relative to conventional practice. Co-application of 6 t ha-1 biochar with 60 kg N ha-1 under no-tillage produced the highest partial N productivity. Conversely, applying N-fertilizer alone under no-tillage resulted in 43 % higher CH4 emission than conventional practice. Across treatments, CH4 emissions contributed 95 % of the total GWP, and soil moisture emerged as the main driver of CH4 fluxes. These findings suggest that applying biochar and N-fertilizer under no-tillage represents a promising pathway to enhance rainfed lowland rice yield and reduce GHG emissions.