Can Phosphorus from Recycled Fertilisers Replace Conventional Sources? An Agronomic Evaluation in Field-Scale Experiments on Temperate Luvisols

Facing phosphate rock scarcity, growing food requirements and pollution problems with phosphorus (P)-containing waste, re-using P as fertiliser is becoming a real need. Innovative fertilisers from sewage sludge ash, animal bones and blood, activated by phosphorus solubilising microorganisms (PSM), were tested in field experiments with winter or spring wheat and compared with commercial fertilisers (superphosphate, phosphorite). Three levels of P doses were established (17.6, 26.4 and 35.2 kg/ha). This paper discusses the fertilisers’ impact on total soil P content and on the P content and P accumulation in wheat grain and straw, weeds and post-harvest residues. Recycled fertilisers maintained soil P stocks and supplied plants with P in the same way as traditional fertilisers, and ensured a comparable P pool in the post-harvest residues to traditional fertilisers. They also did not favour weeds during competitive crop-weed interactions. The PSM included in waste-fertilisers did not exert an evident effect on the soil P content or on the P content and P accumulation in plant biomass. The findings show the potential of recycled fertilisers to act as a substitute to fertilisers from primary sources. Further field research is needed to settle the question of the reasonability of PSM inclusion into fertilisers.