Simulation of regional nitrous oxide emissions from German agricultural mineral soils: A linkage between an agro-economic model and an empirical emission model

Nitrous oxide (N2O) emissions from agricultural land use account for 56% of German agricultural green house gas (GHG) emissions. It is assumed that this share will increase up to 60% by 2020. The realistic estimation of N2O emissions for GHG inventory and policy scenarios requires a model approach which considers the regional drivers for both the N2O originating processes and agricultural production. The nitrous oxide emissions from agricultural mineral soils have been simulated for Germany at regional scale for the base year 2007, the baseline year 2020 and a scenario assuming a nitrogen tax as a mitigation instrument. For the simulation the agro-economic model RAUMIS was applied with the standard IPCC emission factor approach together with the emission model MODE, which provides emission factors considering the regional impacts of climate, soil and crop system. The emission levels computed with the RAUMIS-MODE approach are in general smaller, and indicate a different regional distribution of the highly emitting regions (e.g., in southern Germany). For all of Germany the simulations result in an increase of 16% in the year 2020 computed with the IPCC approach and of 9% computed with the RAUMIS-MODE approach. The simulation of a nitrogen tax of 150% on the price of purchased mineral nitrogen fertilizer results in an emission decrease of 12–13% compared to the baseline. While the impact of the nitrogen tax on agriculture production is highest in regions with low livestock density or low productivity, the mitigation effect in less productive regions is low, and vice versa. The results indicate that a nitrogen tax on mineral fertilizer does not seem to be a suitable instrument to address regional N2O mitigation targets.