Challenges and opportunities for mitigating nitrous oxide emissions from fertilized cropping systems

Nitrous oxide (N 2 O) is often the largest single component of the greenhouse‐gas budget of individual cropping systems, as well as for the US agricultural sector as a whole. Here, we highlight the factors that make mitigating N 2 O emissions from fertilized agroecosystems such a difficult challenge, and discuss how these factors limit the effectiveness of existing practices and therefore require new technologies and fresh ideas. Modification of the rate, source, placement, and/or timing of nitrogen fertilizer application has in some cases been an effective way to reduce N 2 O emissions. However, the efficacy of existing approaches to reducing N 2 O emissions while maintaining crop yields across locations and growing seasons is uncertain because of the interaction of multiple factors that regulate several different N 2 O‐producing processes in soil. Although these processes have been well studied, our understanding of key aspects and our ability to manage them to mitigate N 2 O emissions remain limited.