Wheat growth and phosphorus uptake from polyculture algal biofilms are synergistically modulated by arbuscular mycorrhizal fungi and Serendipita vermifera

Background and aims

Phosphorus (P) from surface waters can be captured in algal biomass, which can be used as a fertilizer. We investigated the efficiency of polyculture algal biofilms produced on municipal wastewater effluent as a P fertilizer for wheat. We asked whether arbuscular mycorrhizal fungi (AMF) and the beneficial root endophyte Serendipita vermifera influence plant performance and P uptake.

Methods

Two pot experiments were performed with wheat fertilized with algal biofilms or highly available triple superphosphate (TSP) at a rate of 37 mg P kg⁻¹, corresponding to 56.8 kg ha⁻¹. In the second experiment, plants were inoculated with AMF (Rhizoglomus irregulare, Funneliformis mosseae, F. geosporum), S. vermifera, or both. P species contained in the algal biofilm and P release dynamics were analyzed by liquid-state ³¹P nuclear magnetic resonance spectrometry and leachate analyses.

Results

Algal biofilms contained high levels of orthophosphate with low water solubility. P recovery by wheat was lower than from TSP, as indicated by plant total dry matter and total P. In algae-fertilized wheat, AMF reduced growth but not P uptake, while S. vermifera in dual inoculation with AMF mitigated the adverse effects. S. vermifera significantly increased root growth and P content in roots when co-inoculated with AMF.

Conclusion

Polyculture algal biomass is an effective, less leaching-prone organic P source for wheat. The synergistic effect of S. vermifera as a root growth-promoting fungus in its interaction with AMF shows the potential and relevance of microbial involvement in using algae-based fertilizers.