Underestimation of Future Agricultural Soil N₂O Emissions and Abatement Needs

Agricultural soils are the largest human-induced source of nitrous oxide (N₂O) due to the extensive fertilizer use in crop production. Despite progress made in global N₂O budget accounting, using the IPCC-derived static emission factors (EF) limits our capability to project future changes in agricultural N₂O emissions and identify cost-effective mitigation strategies. Here, we use a physics-informed AI-driven dynamic EF modeling framework to project direct agricultural soil N₂O emissions induced by mineral fertilizer additions under various climate and nitrogen (N) regulation policy scenarios. Compared to projections based on static EF, our study yields higher future N₂O emissions by 0.3-1.1 Tg N year^-1 across scenarios by 2050, implying greater abatement needs to combat climate change. The gap between static and dynamic EF approaches is projected to widen to 29%-34% by mid-century. Under moderate- to high-ambition N regulation policies, we project that a 25% emission reduction can be reached before 2050, while a 45% reduction is only attainable under high-ambition N policies and strong climate action. The potential for N₂O mitigation due to a policy shift varies substantially among regions, with seven top source regions contributing 76%-87% of global N₂O reduction. Adopting N₂O reduction technologies in hotspot areas would significantly accelerate the timeline for achieving the 25% reduction goal. Improving fertilizer management on croplands can provide climate benefits comparable to, or even exceeding, those of enhancing soil carbon sequestration, particularly in regions with low nitrogen use efficiency. Our findings highlight the higher mitigation potential of targeting N₂O emission hotpots and the urgency of implementing policy shifts.