Long-term trajectories of the carbon footprint of nitrogen use in Mediterranean agriculture

Synthetic nitrogen (N) fertilization has been key in agricultural industrialization by removing N constrains to crop growth, but causes environmental impacts, including GHG emissions. We estimated the carbon (C) footprint of N use in Spanish agriculture from 1860 to 2016, including emissions from industrial fertilizer production, direct soil N2O emissions using Mediterranean-specific factors, and indirect N2O emissions. Overall, the yield-scaled C footprint of N use in Spanish agriculture increased 3-fold, as increased productivity and industrial energy efficiency could not offset the growth in synthetic N use and in N2O emission factors.

The industrialization of agriculture, particularly N fertilizer use, boosted agricultural yields but also N surplus and associated impacts (such as N2O emissions), the dependence on non-renewable resources, and the outsourcing of emissions to other sectors. Spanish agriculture represents a paradigmatic case of agriculture modernization under semiarid conditions with high environmental impacts.