Co-application of struvite with phosphorus-solubilising bacteria enhances soil microbial activity and bioavailable...

Struvite, a phosphorus (P) fertiliser recovered from wastewater, offers a sustainable alternative to non-renewable phosphate rock-derived fertilisers, but its low solubility limits early crop uptake. Co-application with phosphate-solubilising bacteria (PSB) may enhance P release and support the circular nutrient solutions. This study evaluated the effects of co-applying PSB with struvite on P solubility and microbial dynamics in contrasting acidic and alkaline soils. A 28-day soil incubation was conducted using struvite and mono-ammonium phosphate with and without a commercial PSB consortium (containing Bacillus megaterium, Burkholderia spp., and Streptomyces beta-vulgaris). The treatments were assessed for water-soluble-P, pH, CO₂ flux, and bacterial and fungal community composition. Results showed that struvite + PSB significantly increased water-soluble P by 102 % in alkaline soil, associated with decreased soil pH, likely due to PSB-induced acidification. Additionally, PSB induced shifts in microbial communities, enriching native P-solubilising taxa such as Bacillus, Streptomyces, Talaromyces and Penicillium. In contrast, in acidic soil, PSB addition decreased Colwell P and water-soluble P, likely due to microbial immobilisation. Increased microbial respiration under PSB further supports this interpretation. These findings highlight that the effectiveness in enhancing struvite P solubility is soil pH dependent, with greater efficacy in alkaline soil. Field validation, dose optimisation, and crop-specific studies are needed to translate these findings into practical application for sustainable P management.