Closing the Nitrogen Gap: Emissions, Efficiency, and Sensor-Based Monitoring in Agricultural Systems

Global food demand is projected to rise by approximately 56 percent between 2010 and 2050, intensifying reliance on synthetic nitrogen fertilizer during a time when only about half of all applied nitrogen is recovered by crops, with the remainder split between genuine environmental loss and retention within soil and biomass pools. The fraction that is genuinely lost drives substantial economic costs and contributes disproportionately to global nitrous oxide emissions, a greenhouse gas with a warming potential far exceeding that of carbon dioxide. This review synthesizes recent literature across three interdependent domains including nitrogen use efficiency strategies spanning agronomic, genetic, and microbial approaches, decarbonization pathways for ammonia synthesis ranging from conventional to green production routes, and gas sensing technologies for monitoring ammonia and nitrous oxide emissions in agricultural settings. Rather than treating these domains separately, this review proposes that their effects on overall emissions are complementary and potentially compounding rather than strictly additive. Efficiency improvements reduce the total fertilizer volume subject to production emissions, while cleaner production cannot offset nitrogen loss in the field. The exact extent of any combined benefit depends on the relative proportion of field emissions and production emissions within each farming system. Another important finding is the pronounced asymmetry in monitoring readiness. Ammonia sensing has reached field-deployable maturity for detection and concentration monitoring. In contrast, nitrous oxide sensing remains constrained by unresolved challenges in sensitivity and long-term stability despite the gas’s significant contribution to climate change. This asymmetry limits the verification of mitigation outcomes at farm and regional scales. The review further identifies that intervention effectiveness depends on farm structure in the studied context, that global nitrogen policy remains weighted toward incentivizing use rather than reducing pollution, and that the evidence base surveyed here is geographically uneven. Together, these findings indicate that reconciling rising food production with greenhouse gas reduction targets requires integrated frameworks linking field nitrogen budgets, production emissions, and monitoring capability, alongside policy instruments designed around their interdependence.