Le protoxyde d’azote (N2O), puissant gaz à effet de serre émis par les sols agricoles : méthodes d’inventaire et leviers de réduction

Nitrous oxide (N2 O) is a greenhouse gas that mainly originates from soils and agricultural activities. International initiatives require that countries calculate national inventories of their N2 O emissions from agricultural soils. Several methodologies can be applied: (i) Tier I Intergovernmental Panel on Climate Change (IPCC) default approach that only takes into account nitrogen (N) input, (ii) Country-specific methodologies (Tier II and Tier III) that account for regional climatic and land use impacts on N2 O emission factors, and include several sources. Strategies to mitigate N2 O emissions from agricultural soils are based on a rational use of N resource and the stimulation of soil aerobic conditions and biological activity. Management practices to reduce the N2 O emissions should be focused on: (i) Avoiding the soil denitrification process by maximizing soil aeration and reducing their acidity, (ii) Improving N fertilization by reducing free N in soil and optimizing N use efficiency in cropping systems, (iii) Direct actions on the microbial processes by limiting the nitrification process and stimulating the last step of the denitrification process (N2 O reduction to N2 ).