Reducing nitrogen losses in agriculture: integrated modelling of fertilizer and climate change scenarios in Austria

The European Commission has initiated the Green Deal aiming to make the European Union climate-neutral by 2050, with the Farm to Fork strategy being one of its components. Apart from making food systems fair, healthy and eco-friendly, the Farm to Fork strategy targets to reduce nutrient losses and fertilizer use. Previous research has criticized the strategy for its expected negative impacts on European economy, agriculture, and food supply. We add to this research by using an integrated modelling framework to assess the impacts of fertilizer and climate change scenarios on agricultural production and the environment in Austria. The integrated modelling framework consists of the crop rotation model CropRota, the biophysical process model EPIC, and the spatially explicit bottom-up economic land use optimization model BiomAT. Besides other bio-physical and economic datasets, we employ national nitrogen-balance calculations to differentiate between regional and crop specific fertilization intensities as well as mineral and organic fertilizers. We have developed two fertilizer scenarios: a f20 scenario, which considers a uniform 20% reduction of mineral N fertilizer on cropland and grassland, and a fcm scenario, which combines several fertilizer restrictions such as -20% of mineral N fertilizer, a maximum application of 175 kg N ha^-1 on cropland and grassland, and no mineral N fertilizer application on permanent grassland. In addition, we consider four climate change scenarios to support systematic analysis of potential effects of fertilizer reductions on land cover/use, fertilization intensities, potentially harmful nitrogen losses in air, water and soil sediments, and agricultural output. Our scenario results show a total reduction of N losses in air, water and soil sediment by 9% (f20) and 20% (fcm), yet imposed restrictions fall short of an intended 50% reduction. N loss reduction potentials are region, land cover/use and management specific. Magnitudes of N input reductions correspond well to potential N loss reductions to air. N losses to water and soil sediment seem to be determined by precipitation, temperature, and topographic factors. We conclude that agricultural measures need to be tailored to regional and topographic factors in order to effectively reduce nitrogen losses.