Trade-offs of tropical cover crops: enhanced carbon inputs and soybean yield offset higher N2O emissions

Introduction In tropical agriculture, cover crops are increasingly adopted to improve soil health and system resilience. However, their influence on greenhouse gas (GHG) emissions, particularly nitrous oxide (N 2 O), remains underexplored in field conditions. Methods We evaluated how cover crop biomass affects N 2 O emissions and emission intensity (kg CO 2 eq t − ¹ grain) in tropical soybean systems across two field experiments (6 and 10 years) in the Brazilian savannah (Cerrado biome). GHG emissions were measured using static chambers on a weekly basis throughout the cropping seasons from 2022 to 2024. Results Soybeans followed by cover crops such as Mix CC [ruzigrass ( Urochloa ruziziensis ), millet ( Pennisetum glaucum ), and showy rattlebox ( Crotalaria sp ectabilis )] and ruzigrass contributed up to 202% more nitrogen and 51% more carbon inputs than soybeans followed by fallow and maize. The cover crop mix emitted ~6,000 kg C ha − ¹ as biogenic CO 2 in 2 years and 2,655 g N ha − ¹ as N 2 O, ~50%-fold more than the bare fallow. Nevertheless, although high-biomass systems increased N 2 O emissions during the offseason, they also enhanced soybean yield, leading to lower emission intensity. Discussion The structural equation model revealed that cover crop biomass not only had a direct positive effect on soybean yield (standardized coefficient = 0.67) and N 2 O emissions (standardized coefficient = 0.33) but also an indirect negative effect on emission intensity through yield compensation. These findings suggest that adopting cover cropping systems in tropical regions can efficiently contribute to increasing crop yields while improving nitrogen use efficiency, which is important for food security in these regions.