Summary Future phosphorus (P) scarcity and eutrophication risks demonstrate the need for systems‐wide P assessments. Despite the projected drastic increase in world‐wide fish production, P studies have yet to include the aquaculture and fisheries sectors, thus eliminating the possibility of assessing their relative importance and identifying opportunities for recycling. Using Norway as a case, this study presents the results of a current‐status integrated fisheries, aquaculture, and agriculture P flow analysis and identifies current sectoral linkages as well as potential cross‐sectoral synergies where P use can be optimized. A scenario was developed to shed light on how the projected 2050 fivefold Norwegian aquaculture growth will likely affect P demand and secondary P resources. The results indicate that, contrary to most other countries where agriculture dominates, in Norway, aquaculture and agriculture drive P consumption and losses at similar levels and secondary P recycling, both intra‐ and cross‐sectorally, is far from optimized. The scenario results suggest that the projected aquaculture growth will make the Norwegian aquaculture sector approximately 4 times as P intensive as compared to agriculture, in terms of both imported P and losses. This will create not only future environmental challenges, but also opportunities for cross‐sectoral P recycling that could help alleviate the mineral P demands of agriculture. Near‐term policy measures should focus on utilizing domestic fish scrap for animal husbandry and/or fish feed production. Long‐term efforts should focus on improving technology and environmental systems analysis methods to enable P recovery from aquaculture production and manure distribution in animal husbandry.

Phosphate rock is a non-renewable source of phosphorus (P) in mineral fertilizer and many countries need to use P fertilizer more efficiently in food production. This study explored the theoretical fertilizer potential of the P-rich bioresources animal manure and sewage sludge to supply the required P fertilizer for crops. We used Norway as a case study and employed multi-regional substance flow analysis with averaged annual data for the period 2009-2011. In a status quo soil balance for agricultural soil, all counties had a positive balance with a national average of 8.5 (range between counties of 2.7-14.7) kg P ha-1. In addition, two fertilizer regimes (FR) were evaluated for the period; FR1 omitted mineral P fertilizer from the balance and assumed bioresource addition matched plant P offtake regardless of soil available P, while FR2 omitted fertilizer from the balance and adjusted bioresource inputs according to whether soil available P was above (adjusted downwards) or below (adjusted upwards) the optimum soil P level. FR1 and FR2 gave a national average P surplus of 1.2 (range-7.0 to 11.2) and 6.2 (range-2.5 to 19.0) kg P ha-1 , respectively. The secondary P fertilizer potential of bioresources for meeting P requirements was found to be underestimated in the short term by not taking into account the actual plant-available soil P level. Our conclusion was that the P fertilizer values of manure and sludge have the theoretical potential to meet the P fertilizer requirements of all Norwegian crops assessed in both the short-term and long-term perspective.

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