Organic farming systems rely on the efficient use anrecycling of resources. Currently, nutrients like phosphorus (P) are used only once to produce food and subsequently, lost due to poor recycling. Current regulations concerning the use of alternative P fertilizers are strict, restricting e.g. the use of municipal organic wastes and hampering e.g. the use of sewage sludge due to concerns about heavy metals and other pollutants. However, there is an urgent need to improve the recycling of P from urban areas back to cropland, as the worldwide P reserves are very limited. Furthermore, improvement of agronomic P efficiency due to the choice of P efficie cultivars and agronomic methods (e.g. P mobilization by cover cropping, application of microorganisms suited to enhance plant P uptake) is the second pillar of improved P efficienc
