Phosphorus dissolution and diffusion from struvite and its impact on phosphorus availability in Acrisol and Cambisol soils

There is a growing interest in recovering and recycling phosphorus (P) from waste streams to reduce reliance on finite and non-renewable phosphate rock in agriculture. Struvite, derived from waste streams, has emerged as a potential alternative P fertilizer. However, its behaviour in soil remains unclear. This study aimed to investigate the behaviour and effectiveness of struvite as a P fertilizer in acidic Acrisol and calcareous Cambisol soils, focusing on the P dissolution from struvite, struvite P diffusion in soil and P availability. Our findings revealed that the P dissolution from struvite in solution is pH-dependent, with the most dissolution observed at pH 4.5 and significantly less at pH 7.0 and pH 8.5. Consequently, P dissolution from struvite was more rapid in the Acrisol compared with the Cambisol. This was supported by the increased accumulation of water-soluble P in the Acrisol and acid-extractable P in the Cambisol within the 0–1 cm concentric soil section surrounding the struvite application site, as demonstrated in the petri dish experiment. However, the Acrisol exhibited a gradual decrease in P diffusion over time, in contrast to the Cambisol, which showed an increasing trend. This can be attributed to the stronger P fixation observed in the Acrisol. The application of struvite resulted in increased soil P availability, as determined by the diffusive gradients in thin films (DGT) technique, particularly in the Acrisol where struvite was concentrated. Furthermore, the presence of organic acids enhanced struvite P availability in both Acrisol and Cambisol soils. These findings contribute to a better understanding of struvite behaviour in different soil environments and provide valuable insights for optimizing its use as a sustainable and efficient P fertilizer.