National Nutrient Balances in the Baltic Sea Region

The calculation of nutrient balances has been used as an environmental indicator for agriculture for many years. Particularly, nitrogen balances/surpluses have been established as one of the few generally accepted key indicators for the documentation and analysis of the sustainability of agriculture production. Hence, nutrient balances at national level can be used for communicating changes of agricultural production and related impacts on the environment, showing trends in the effectiveness of nutrient use over time, identifying the factors affecting the nutrient surpluses or deficits and to compare individual countries. The latter one is particularly crucial because water sources and air are not restricted within national boundaries and thus, tackling problems of emissions into waters and air need a transnational approach. However, different approaches of calculating nutrient balances can lead to different results due to differences in methods and data. This must be considered when comparing countries. Hence, one objective of the Manure Standards project was to calculate nutrient balances for the participating Baltic Sea Countries based on different methods, to compare them, identify the differences and based on that, to give recommendation which method should be used in all Baltic Sea countries. For this, three methods were selected: (1) gross nutrient balance according to OECD/Eurostat (Eurostat, 2013) (2) a nitrogen balance approach currently used in Germany – NBA (Bach et al., 2011; Hausermann https://www.bmel-statistik.de/fileadmin/daten/MBT-0060000-2019.pdf), and (3) the net anthropogenic nitrogen- and phosphorus inputs (NANI and NAPI) approach according to Hong et al. (2017). Results reveal differences in the level of the nitrogen and phosphorus surpluses (or deficits) for each country depending on the method used. This highlights the importance of considering different material system boundaries when comparing nutrient balances across countries. Only results based on the same method should be compared. However, calculations also show that even the recalculation of different approaches to a comparable material system boundary can lead to different results due to differences in the data and coefficients used. Currently, the gross nutrient balance according to OECD/Eurostat is the only comparable parameter for the nitrogen and phosphorus balances of BSR countries. However, as only OECD and EU Member States report respective data for the gross nitrogen balance (GNB) and gross phosphorus balance (GPB), not all BSR countries can be compared on this parameter (e.g. Russia is missing). As the majority of BSR countries 4 already use this approach, adopting it for all BRS countries should be the option with the lowest additional efforts to get a common method for calculating national nutrient balances in the BSR. However, also the two other approaches used in this project have their justifications in the discussion about a common method for the calculation of national nutrient balances. The nitrogen balance approach currently used in Germany calculates not only a field balance, but also a stable balance (and a biogas balance), which in turn can be summed up to the total national nitrogen balance. Hence, this approach is more sophisticated compared to the approach of OECD/Eurostat and thus, offers the opportunity to analysis nutrient flows between the production sectors within the whole agricultural sector in more detail. However, the close exchange with the work package activity partners revealed some problems of data availability and reliability related to the additionally needed data of fodder production and feed imports. For the net anthropogenic nitrogen and phosphorus inputs approach (NANI and NAPI), data requirements are lower compared to the other ones, because country-specific coefficients can be taken from Hong et al. (2012; 2017) and much information from the Eurostat database can be used. However, compared to the other two approaches, data and coefficients used are often less detailed and thus, balance results could be less precise. Hence, this approach is very useful for calculating nutrient balances when data is rare or when aiming to compare many countries. Overall, results identified livestock manure production as one of the major sources of nutrient inputs. Thus, improving the precision of manure use offers a high potential for getting to a more effective nutrient management strategy in the BSR and is a key issue to instantly reduce nutrient inflow into the Baltic Sea.