The Circular Phosphorus Economy: Agronomic Performance of Recycled Fertilizers and Target Crops

Abstract

Background: The circular phosphorus (P) economy addresses economic and environmental penalties inherent to the current linear P economy. Phosphorus sources recovered from waste steams (recyclates) offer an alternative to conventional fertilizers. Aim: This research aimed to assess the agronomic performance of P recyclates derived from wastewater (hazenite, struvite), treated sewage sludge ash (SSA) and compost (FOGO food organics/garden organics) with crops previously characterized for P use efficiency (PUE). Methods: Phosphorus was supplied as granules and benchmarked against conventional fertilizers or mineral solution. Grown in controlled conditions, crops received recyclates individually or as amalgamates, with or without additional water-soluble P. We quantified P uptake, yield and phytate content, and calculated agronomic performance indicators. Results: Results revealed that (1) crop genotypes with purportedly lower or higher PUE showed similar performance when grown with limiting P supply and/or less soluble P recyclates, (2) crop performance improved when less soluble P recyclates were combined with water-soluble P, (3) crops produced similar yield and biomass when supplied with an organo-mineral formulation, hazenite, or conventional fertilizer, (4) grain accumulated higher levels of the antinutrient phytate with excess soluble P. Conclusion: We conclude that suitably formulated P recyclates can supplement or replace conventional fertilizers, and that fertilizer design should consider the solubility of recyclates and a crop's ability to access less soluble P. This adds to the growing body of evidence that well-formulated next-generation fertilizers can efficiently nourish crops. Integrating insights from controlled experiments and field trials is a cost-effective strategy to actualize the circular P economy.