Phosphorus (P) flow from deposits through agriculture to waterways leads to eutrophication and depletion of P reserves. Therefore, P must be recycled. Low and unpredictable plant availability of P in residues is considered to be a limiting factor for recycling. We identified the determinants for the plant-availability of P in agrifood residues. We quantified P in Italian ryegrass (Lolium multiflorum) and in field soil fractions with different plant availabilities of P as a response to manure and sewage sludge with a range of P capture and hygienization treatments. P was more available in manure and in sludge, when it was captured biologically or with a moderate iron (Fe)/P (1.6), than in NPK. Increasing rate of sludge impaired P recovery and high Fe/P (9.8) prevented it. Anaerobic digestion (AD) reduced plant-availability at relevant rates. The recovery of P was increased in AD manure via composting and in AD sludge via combined acid and oxidizer. P was not available to plants in the sludge hygienized with a high calcium/P. Contrary to assumed knowledge, the recyclability of P in appropriately treated residues can be better than in NPK. The prevention of P sorption in soil by organic substances in fertilizers critically enhances the recyclability of P.

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a b s t r a c tRecent research suggests that anthropogenic nutrient flows may have transgressed the regulatory capacity of the earth. Agrifood systems account for most of the flows, and the food supply is limited more by reducing the excessive flows than by phosphorus (P) reserves or population growth. The food supply is limited primarily by the P flow tolerated by freshwater ecosystems and next by the needed reduction in the conversion of nitrogen (N) to reactive form in fertilizer manufacture, legume cultivation and fossil fuel combustion. The required reduction in P and N flows would reduce the food supply to 250 and 710 kcal capita À 1 d À 1 , respectively, in the current agrifood systems. Dietary changes, waste prevention and nutrient recycling are parts of the necessary transformation.

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