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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Anthropogenic nutrient flows exceed the planetary boundaries. The boundaries and the current excesses vary spatially. Such variations have both an ecological and a social facet. We explored the spatial variation using a bottom-up approach. The local critical boundaries were determined through the current or accumulated flow of the preceding five years before the planetary boundary criteria were met. Finland and Ethiopia served as cases with contrasting ecology and wealth. The variation in excess depends on historical global inequities in the access to nutrients. Globally, the accumulated use per capita is 2300 kg reactive nitrogen (N r ) and 200 kg phosphorus (P). For Finland, the accumulated use per capita is 3400 kg N r and 690 kg P, whereas for Ethiopia, it is 26 kg N r and 12 kg P. The critical N boundary in Finland is currently exceeded by 40 kg cap −1 a −1 and the accumulated excess is 65 kg cap −1 a −1 , while the global current excess is 24 kg cap −1 a −1 and there is space in Ethiopia to increase even the accumulated flow. The critical P boundary is exceeded in Finland and (although less so) in Ethiopia, but for contrary reasons: (1) the excessive past inflow to the agrifood system in Finland and (2) the excessive outflow from the agrifood system triggered by deficits in inflow and waste management in Ethiopia. The critical boundaries set by Finnish marine systems are lower and those set by freshwaters are higher than the planetary boundaries downscaled per capita. The shift to dominance of internal loading in watercourses represents a tipping point. We conclude that food security within the safe boundaries requires global redistribution of nutrients in residues, soils and sediments and of rights to use nutrients. Bottom-up assessments reveal local dynamics that shed new light on the relevant boundary criteria and on estimates and remedies.

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Nitrogen (N) and phosphorus (P) cycles are absolutely vital in maintaining sustainable food systems. Human activities disturb the natural balance of these cycles by creating enormous additional nutrient fluxes, causing eutrophication of waterways and pollution in land systems. To tackle this problem, sustainable nutrient management is required. This paper addresses sustainable nutrient management in two countries: The Netherlands and Finland. We adopt a critical perspective on resource politics, especially towards opportunistic policy strategies for the pollutant management of N and P. Two research questions are considered. First, what are the key systemic and policy failures that occurred in the N and P systems in the Netherlands and Finland between 1970 and 2015? And second, which lessons can be drawn when addressing the policy responses in the two countries to cope with these failures? The cases are analyzed within Weber and Rohracher's framework that addresses "failures" preventing sustainable transitions. The results show that a number of failures occurred, besides market failures (over-exploitation of the commons, externalization of costs): lack of directionality, policy coordination, institutions, capabilities, infrastructure, demand articulation, and reflexivity. Policy responses in both countries resulted in ponderous policy frameworks that were adequate to tackle nutrient problems from the industrial sector and municipalities. However, both countries provided only a moderate response in terms of system-wide integrated policy frameworks to cope with sectoral-transcending issues. The agricultural use of N and P, in contrast to detergents, has not been subjected to strong regulatory measures.