From field measurements to national inventories and smart incentives—the SmartField approach for agricultural soil N ₂ O fluxes

Abstract Significantly reducing greenhouse gas (GHG) emissions from agricultural production is crucial to limiting climate change. Fertilized soils are a major source of nitrous oxide (N 2 O), a potent GHG. Reducing N 2 O emissions is a key interest for many countries, including Denmark, where approximately 90% of N 2 O emissions originate from agricultural soils. Although the link between nitrogen (N) fertilization and N 2 O emissions is well-known, quantitative evidence for the efficiency of mitigation options in the relevant local context is scarce. This is often due to high flux variation over time scales ranging from hours to a few days. Previous studies have mostly neglected to perform measurements that could to account for this variation. Furthermore, reducing N 2 O fluxes can result in increased losses through ammonia (NH 3 ) volatilization and N leaching, as well as reduced yields. Thus, establishing tangible mitigation strategies requires a holistic understanding of N 2 O fluxes in the context of the annual, field-scale N balance, translation of findings into modeling approaches, use of models to identify emission hotspots, and scaling interventions from the field to regional and national levels. Here, we introduce the SmartField initiative, which aims to reduce national N 2 O emissions in Denmark by 20%–30% by 2030 by testing and providing verified, field-tested mitigation options. The initiative includes accurate and transparent N 2 O emissions accounting at the field, farm, and national levels and a setup to test management technologies for N 2 O emissions. It also involves developing a monitoring, reporting, and verification system for N 2 O emissions based on a Tier 3 methodology. Furthermore, SmartField collaborates closely with farmers, value chain actors, and policy makers to identify synergies and trade-offs between reducing GHG emissions and their effects on the environment, food production, and farm profitability.