A field experiment was conducted to investigate the effect of biochar on maize yield and greenhouse gases (GHGs) in a calcareous loamy soil poor in organic carbon from Henan, central great plain, China.

Biochar was applied at rates of 0, 20 and 40 t ha⁻¹ with or without N fertilization. With N fertilization, urea was applied at 300 kg N ha⁻¹, of which 60% was applied as basal fertilizer and 40% as supplementary fertilizer during crop growth. Soil emissions of CO₂, CH₄ and N₂O were monitored using closed chambers at 7 days intervals throughout the whole maize growing season (WMGS).

Biochar amendments significantly increased maize production but decreased GHGs. Maize yield was increased by 15.8% and 7.3% without N fertilization, and by 8.8% and 12.1% with N fertilization under biochar amendment at 20 t ha⁻¹ and 40 t ha⁻¹, respectively. Total N₂O emission was decreased by 10.7% and by 41.8% under biochar amendment at 20 t ha⁻¹ and 40 t ha⁻¹ compared to no biochar amendment with N fertilization. The high rate of biochar (40 t ha⁻¹) increased the total CO₂ emission by 12% without N fertilization. Overall, biochar amendments of 20 t ha⁻¹ and 40 t ha⁻¹ decreased the total global warming potential (GWP) of CH₄ and N₂O by 9.8% and by 41.5% without N fertilization, and by 23.8% and 47.6% with N fertilization, respectively. Biochar amendments also decreased soil bulk density and increased soil total N contents but had no effect on soil mineral N.

These results suggest that application of biochar to calcareous and infertile dry croplands poor in soil organic carbon will enhance crop productivity and reduce GHGs emissions.