Reducing nitrogen and phosphorus inputs to the Baltic Sea by better using manure in agriculture

What is it about?

We used "budgets" of nitrogen and phosphorus for regions around the Baltic Sea to estimate how efficiently the nutrients in manure and commercial fertilizer are used to produce crops. We found that manure was not being used efficiently and/or that over-application of nutrients was occurring in many areas. Based on this analysis, we estimated the potential to reduce nitrogen and phosphorus inputs to sub-basins of the sea (Baltic Proper, Gulf of Finland, Gulf of Riga). In other words, there are more than enough nutrients to produce crops in the region, but the nutrients aren't distributed where the crops need them. This situation increases the risk that nutrients leak to the sea and contribute to eutrophication. We estimate that by moving manure nutrients to where they are needed (and reducing commercial fertilizer imports) it is possible to make progress towards Baltic Sea Action Plan goals, meeting about 50-80% of nitrogen reduction targets and 40-60% of phosphorus reduction targets (depending on scenario).

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Why is it important?

While there has been great progress in reducing nutrient loads to the Baltic Sea over the past several decades, further reductions are needed to meet the goals of the Baltic Sea Action Plan. Agriculture is currently the largest sources of new nutrients to the sea. We show in this analysis that further reductions are possible in the agricultural sector by reducing over-fertilization in some regions. This is accomplished by redistributing manure from areas with many animals relative to cropland to areas that focus on crop production and would otherwise need to import fertilizer.

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