Abstract
Agricultural soils represent both a major source of anthropogenic greenhouse gas (GHG) emissions and a vital reservoir for atmospheric carbon sequestration. This study presents a comprehensive two-year field evaluation examining the interactive effects of hardwood biochar application (10 t ha⁻¹) and winter cereal rye (Secale cereale L.) cover cropping within a temperate corn-soybean (Zea mays L. – Glycine max L.) crop rotation. We investigated four experimental treatments: fallow control, cover crop alone, biochar alone, and a combined biochar-cover crop system. Continuous static-chamber trace gas measurements and high-resolution soil core analysis revealed significant synergistic benefits in the combined treatment. Over the 24-month study period, the integrated biochar and cover crop system increased total soil organic carbon (SOC) in the top 15 cm by 28.4% compared to the control, outperforming the additive individual responses of biochar (+16.2%) and cover crop (+8.5%) alone. Furthermore, cumulative nitrous oxide (N₂O) emissions were suppressed by 41.2% in the combined treatment relative to the control, driven by enhanced soil aeration, altered microbial denitrification pathways, and reduced nitrate leaching. Crop yield metrics remained stable, with no statistical penalties observed in either corn or soybean phases. These findings demonstrate that co-deploying biochar with cover crops constitutes an effective, scalable technological strategy for climate-smart agriculture, simultaneously enhancing carbon sink capacity and mitigating potent non-CO₂ greenhouse gases without compromising agronomic productivity.
