Phosphorus Release from Nano-Hydroxyapatite Derived from Biowastes in the Presence of Phosphate-Solubilizing Bacteria: A Soil Column Experiment

Phosphorus applications in agriculture can lead to significant environmental impacts, necessitating a revolution in current agricultural practices. This study explores the potential of hydroxyapatite nanoparticles (nHAPs) synthesized from poultry bones as P fertilizers. nHAPs were produced at 300 °C (nHAP₃₀₀) and 700 °C (nHAP₇₀₀), and their effectiveness was evaluated. An in vitro solubilization test with Pseudomonas alloputida evaluated the bacterium’s ability to solubilize the nanoparticles, assessing dissolved P and organic acids produced. Additionally, a soil leaching test measured P losses and bioavailable P in soil compared to a conventional fertilizer, the triple superphosphate (TSP). nHAP₃₀₀ displayed heterogeneous sizes, while nHAP₇₀₀ were approximately 100 nm in size, with a P content of 8.8% and 19.4%, respectively. Pseudomonas alloputida successfully solubilized both types of nanoparticles, with nHAP₇₀₀ demonstrating a higher solubility than nHAP₃₀₀. The TSP treatment resulted in higher P losses (6.35 mg) compared with nHAP treatments (nHAP₃₀₀ 0.32 mg; nHAP₇₀₀ 0.28 mg), indicating the potential of nHAP for recycling P from waste. Our findings indicate that nHAP₇₀₀ are more efficient in P release than nHAP₃₀₀ but less prone to leaching compared to conventional fertilizers. Utilizing these nanoparticles enables phosphorus recovery from waste and holds significant potential for sustainable agricultural applications.