Strategies for Reducing Nitrogen and Phosphorus Losses

Imports from abroad were incorporated into Switzerland’s farm-gate-budget-based agricultural nutrient budget calculation to expand it into a food-system budget. This allows assessment of self-sufficiency, nutrient use and circularity to be assessed in addition to nutrient surpluses.

The farm-gate budget is used to assess the nutrient flows of a country, region or farm. In Switzerland, it is also used at national level as an agricultural policy target indicator.  Among others, it covers inputs and outputs of nitrogen (N) and phosphorus (P) from feed, fertilisers, the purchase and sale of animals, and agricultural production.

This study expanded the system boundaries of the budget calculation by including food production and waste streams. Consequently, it also included the import, consumption and recovery of nutrients abroad. Based on different scenarios, the scope and potential for reducing losses were discussed:

1. Business as usual (BAU) – growing demand for food whilst production remains steady.
2. Optimised nutrient management – agricultural best-practice methods for increasing agricultural nutrient-use efficiency in livestock production, farm-manure management and fertilisation in plant production.
3. Food-waste reduction – reducing food losses across the entire food chain as a strategy for increasing resource-use efficiency and self-sufficiency.
4. Circular agriculture – plant production focuses on human nutrition. By-products are used as fertilisers and animal feed, and animal production is meant to be primarily grassland-based.
5. Combination – combines the strategies of food-waste reduction, circular agriculture and optimised nutrient management.

The results show that Swiss food consumption leads to significant nutrient surpluses not only in Switzerland but also abroad. Since Switzerland imports more feed and food than it exports, additional nutrient surpluses of around 37,000 tonnes of N and 2700 tonnes of P, i.e. 35% and 66%, respectively, are generated inside the country, are produced abroad. 

Combining the strategies with the highest potential

The three strategies – optimised nutrient management, circular agriculture with a plant-based diet and the combination of these two – proved effective for reducing internal nutrient surpluses compared to the present-day and ‘business as usual’ scenarios, achieving reductions of around 30%, 18% and 44% for nitrogen and 32%, 5% and 53% for phosphorus. Furthermore, they yield an improved degree of self-sufficiency. Future studies could focus on determining the most efficient production systems, thereby helping to develop and justify effective strategies.

Implementing these strategies is challenging, especially since agriculture is a heterogeneous sector with different types and sizes of farms and different geographic, socioeconomic and cultural framework conditions. What’s more, external factors (e.g. fertiliser and feed prices) influence the feasibility of the individual and combined measures.

Whereas technical and highly concrete measures such as the covering of slurry tanks or the optimisation of fertilisation can be implemented relatively quickly, strategic changes in sectors such as the conversion of cultivation and husbandry systems or even changes in the population’s diet require more time. It is important to bear this in mind when selecting, prioritising and combining measures.