Nitrous oxide emissions and nitrogen budgets for German agricultural soils via process-based modelling

Agricultural soils are the dominant source of nitrous oxide (N₂O) emissions in most countries, but the spatial and temporal heterogeneity of the emission fluxes makes their quantification challenging. Here we develop a framework for estimating national N₂O emissions at high spatial resolution, based on the biogeochemical-model LandscapeDNDC. We apply this framework to Germany, making use of high resolution datasets for soil type, agricultural management practices, climate and nitrogen (N) deposition. Compared to the current emission-factor (Tier-2) approach for compiling an N₂O inventory, our method results in similar but slightly lower total N₂O emissions at the national scale, but higher fertiliser-driven emissions, which are critical for UNFCCC reporting. It is also able to capture the effect of yearly climate variation. Spatial disaggregation of the emissions into approximately 400 districts reveals large differences at the sub-national scale, where the process-based model accounts better for local variations in soil, climate and agricultural management. We also go beyond the focus on N₂O emissions and determine a full N budget for Germany, which includes the quantification of environmentally important N fluxes such as ammonia volatilisation, nitrate leaching and NO emissions.