Quality Traits of Lettuce and Radish Fertilized with Struvite

Phosphorus scarcity necessitates sustainable alternatives like struvite (MgNH4PO46H2O) recovered from waste streams. This study evaluated the efficacy of waste-derived organo-mineral fertilizers containing struvite on greenhouse-grown baby leaf lettuce (Lactuca sativa L.) and radish (Raphanus sativus L.) quality in Bosnia and Herzegovina, Italy, and Spain. Results demonstrated that struvite performed comparably to or better than conventional inputs, significantly increasing P concentration in radish across all sites (up to ∼4 g kg–1 DW) and in lettuce in most locations. Struvite maintained or enhanced photosynthetic profiles, maximizing total chlorophyll in B&H and Italy lettuce. Multivariate analysis (PLS-DA) revealed crop-specific metabolic shifts, notably reducing lipid peroxidation (malondialdehyde) in struvite-fertilized lettuce in specific regions while enhancing radish antioxidant flavonoids in Italy (reaching ∼1.2 mg CE g–1 FW). Struvite consistently proved to be a highly bioavailable P source that maintains or enhances vegetable nutritional and antioxidant quality, facilitating the transition toward circular agricultural systems.