Biofertilizers are the preparations of live microorganisms added to the root, seed or soil to promote plant growth. In this study, Plant Growth Promoting Bacteria able to solubilize insoluble phosphate (P) and potassium (K) forms were isolated, characterized and identified. Two isolates that demonstrated excellent solubilization of potassium or phosphate from abundant and bio-available waste biomass (rice husk and cattle bone) were used to produce biofertilizers by solid-state fermentation. The biofertilizers were applied to grow three food security crops, Zea mays, Solanum lycopersicum, and Arachis hypogea, in a screenhouse, and monitored for growth impacts. Treatments A, B, and A + B biofertilizers caused a significant (p < 0.05) increase in plant dry weights. The highest microbial colonization was obtained from treatment A + B (for S. lycopersicum) with a microbial count (log 2.89 (108) cfu/g), whereas treatment with B (for A. hypogea) had the least microbial count (log 2.73 (108) cfu/g). Maximum values of experimental parameters: shoot height, leaf number, plant dry weight and leaf width were obtained with the combined application of both biofertilizers. P and K solubilizing PGPB have shown potential for use as biofertilizers in growing these key crops under the soil conditions and in the environment studied.
Keywords: Bacillus cereus; Biofertilizers; Pseudomonas aeruginosa; rhizosphere; rice husk.
This work demonstrates a first, sensitive and reliable method for low-cost, sustainable, eco-friendly production and utilization of biofertilizers for improved growth of major tropical food security crops using native bacterial strains in a defined tropical agronomic environment. Its novelty is the choice of Bacillus cereus and Pseudomonas aeruginosa singly and in combination (synergy/additive) as biofertilizers for growing tropical test crops. It also demonstrated the use of a novel and cheap delivery method/carrier that ensured the establishment and persistence of PGPB in the rhizosphere. Native B. cereus and P. aeruginosa were able to solubilize and make available to plants phosphate and potassium, thereby improving soil quality and plant growth while the process achieved the reuse of waste biomass.