Exploring the potential for nitrogen fertilizer use mitigation with bundles of management interventions

Mineral nitrogen (N) fertilizer use is essential to maintain high-yielding cropping systems that presently provide food for nearly half of humanity. Simultaneously, it causes a range of detrimental impacts such as greenhouse gas emissions, eutrophication, and contamination of drinking water. There is growing recognition of the need to balance crop production with the impacts of fertilizer use. Here we provide a global assessment of the potential to reduce mineral fertilizer use through four interventions: capping surpluses, enhancing manure cycling to cropland, cultivation of off-season green manures, and cycling of human excreted N to cropland. We find that the combined potential of these interventions is a reduction in global N fertilizer use by 21-52%. The availability of interventions is spatially heterogeneous with most cropland having three to four interventions available with alternative N sources tending to be more abundant on cropland already receiving fertilizer. Our assessment highlights that these locally in part already practiced interventions bear great opportunities to mitigate synthetic N use and dependency globally. Yet, their limited adoption underpins the need for cross-sectoral policies to overcome barriers to their implementation and agronomic research on their robust scaling.