Phosphate-solubilizing bacteria increase maize phosphorus uptake from magnesium-enriched poultry manure biochar

Manure-derived biochars have a fertilizer potential as pyrolysis concentrates non-volatile nutrients. The addition of magnesium (Mg) to poultry manure enhances its Mg/Ca ratio and could increase soluble P by phosphate-solubilizing bacteria (PSB). Our objective was to assess the potential of PSB strains to solubilize P from both unenriched and Mg-enriched biochar and to evaluate the growth of maize in an Oxisol fertilized with biochar (100 mg kg⁻¹ total P) to satisfy plant P needs. We examined the strains: Paraburkholderia fungorum UFLA 04–155, Pseudomonas anuradhapurensis UFPI B5-8A, Paenibacillus chondroitinus UFLA 03–116, Acinetobacter pittii UFLA 03–09, and Rhizobium tropici CIAT 899. Biochar was made from poultry manure at temperatures of 350 °C, 500 °C, and 650 °C. Maize growth and P uptake were assessed in plants after 15 and 30 days under greenhouse conditions. The strain P. anuradhapurensis UFPI B5-8A significantly released more P from Mg-biochar (82% of the total P added) than from the unenriched biochar (74% of the total P added). Furthermore, this strain released tartaric and gluconic acids when mixed with the Mg-biochar, whereas malic acid was primarily exuded when applied to unenriched biochar. Similarly, P. anuradhapurensis UFPI B5-8A inoculation or Mg enrichment resulted in a 20% increase in P uptake by maize compared to unenriched biochar. Therefore, a synergistic approach using Mg-biochar and inoculation with PSB increases phosphate availability from poultry manure and maize P use efficiency.