Heading towards a Regionalised Nitrogen Balance

The newly designed Swiss agri-environmental monitoring programme ‘MAUS’ aims, as far as possible, to determine environmental impacts for regions and farm types with existing data. The first MAUS report deals with the regionalised nitrogen balance.

Since 2009, Agroscope has used indicators to record the environmental impacts of agriculture for different regions and farm types on behalf of the Swiss Federal Office for Agriculture (FOAG). Until 2023 the environmental indicators were calculated using the data from 300 farms (Swiss Agri-Environmental Data Network, SAEDN). In 2023 the monitoring programme was renamed MAUS (based on the German acronym for ‘Monitoring of the Swiss Agri-Environmental System’) and it is now based as far as possible on existing data sources. Any data gaps are filled with specific surveys.

One of the environmental indicators calculated in MAUS is the soil-surface balance for nitrogen (nitrogen balance). This describes the difference between the amount of nitrogen supplied to the soil and the amount of nitrogen withdrawn from the soil in the form of agricultural products. A positive nitrogen balance shows a nitrogen surplus, which can have negative effects on the environment (e.g. (eutrophication of ecosystems, greenhouse-gas effect) and on the health of the population (e.g. nitrate content in drinking water, formation of particulates).

Nitrogen balance calculated using existing data

The nitrogen soil-surface balance for 2021 was calculated in MAUS to test the methodology and highlight any need for improvement. Data from the Agricultural Policy Information System (AGIS), from the programme for farmyard manure and recycled fertiliser transfers (HODUFLU), georeferenced usage data from the Cantons and data from various sectoral organisations served as the primary information sources here. These were used to calculate the nitrogen balances at farm level for all Swiss farms, after which the results were aggregated at the desired level (e.g. regions, agricultural zones).

Results varied significantly between Cantons: those with intensive animal husbandry had higher nitrogen surpluses, whilst mountain regions had lower ones. As a rule, surpluses showed a downward progression from the lowland region to the hilly region to the mountain region to the summer-grazing area.

Comparison with other balances

To validate the method, results were aggregated at national level for comparison with the national soil-surface balance of the Swiss Federal Statistical Office (SFSO). The MAUS calculation yielded an average nitrogen surplus of 40 kg nitrogen per hectare across the entire agricultural area of Switzerland (utilised agricultural area and summer-grazing area), or 57 kg nitrogen per hectare utilised agricultural area (UAA) excluding summer-grazing area. These figures are markedly lower than those of the SFSO (66 kg nitrogen per hectare of agricultural land, 90 kg nitrogen per hectare UAA). The findings are the same when one compares MAUS calculations with Agroscope’s national farm-gate balance.

Like Agroscope, the SFSO also calculated regionalised balances, but using a different approach: whilst Agroscope calculated values at farm level and then aggregated these at a higher level (e.g. at cantonal or national level – i.e. a ‘bottom-up’ approach), the SFSO broke the national figures down into those of the different Cantons (i.e. a ‘top-down’ approach). Thus, although the absolute values differ between the two approaches, the percentage distribution of the inputs and outputs between the Cantons are largely in agreement.

Mineral fertiliser use calculated differently

The lower figures for the MAUS calculations can largely be explained by the fact that MAUS underestimates the nitrogen inputs from mineral fertilisers (27% lower figures than those of the SFSO). MAUS determines mineral fertiliser use by calculating the nitrogen input at farm level based on crop-specific average fertiliser values. By contrast, the SFSO estimates mineral fertiliser use based on import figures. The next few years will see the continuous refinement of the method for calculating the nitrogen balance in MAUS. Thanks to additional data surveys (satellite data, data from farm-management information systems, online surveys) – including surveys on mineral fertiliser use – data gaps will be filled, and more accurate data will be available. The aim over the next few years is to highlight and gain a better understanding of the reasons for the differences between the regional and national input and output figures as well as the differences between Cantons.

Difference between a farm-gate balance (a) and a soil-surface balance (b).