Reducing greenhouse gas emissions from North American soybean production

The agricultural sector is responsible for substantial amounts of greenhouse gas emissions that exacerbate climate change. Such greenhouse gas emissions from upland crops are difficult to abate because they are dominated by nitrous oxide (N2O) production from soil processes. Strategies to reduce these emissions focus on N fertilizer management, and there is a widespread assumption that legume crops, which do not receive N fertilizer, emit little N2O. Here we show that this assumption is incorrect; approximately 40% of N2O emissions from the most extensive cropping system in North America—the maize–soybean rotation—occur during the soybean phase. Yet, due to the lack of N fertilizer input, opportunities for emissions abatement from the soybean phase are unclear. Using models of cropping systems, we developed a strategy that combines cover-crop management and earlier planting of extended growth soybean varieties to reduce emissions from soybean production by 33%. These practices, which complement N fertilizer management in maize, are widely accessible and represent an immediate, climate-smart strategy to reduce nitrous oxide emissions from soybean production, thus not only contributing to climate-change mitigation but also maintaining productivity while adapting to changing weather patterns.