Co-Inoculation with Phosphate-Solubilizing Microorganisms of Rock Phosphate and Phosphogypsum and Their Effect on Growth Promotion and Nutrient Uptake by Ryegrass

In the previous half-century, natural rock phosphates (PN) have been a valuable alternative for phosphorus (P) fertilizer for sustainable agriculture; furthermore, phosphogypsum (PG) has been widely used as a soil amendment fertilizer since it improves some soil properties, increases crop yields, and represents an environmental concern that can make a good economic profit; this research aimed to study the effects of microbial consortia of phosphate-solubilizing microorganisms (PSM) on the solubilization of PN and PG in the soil, and their effects on promoting plant growth and nutrient assimilation using ryegrass as a plant model. Local supply of PG with Pseudomonas fluorescens (MW165744) significantly increases root proliferation and plant biomass dry weight compared to other isolates, as well as improves total P uptake, with a maximum value of 62.31 mg/pot. The opposite occurred in mixing inoculation with Pseudomonas fluorescens, Pantoea agglomerans (MW165752) and Stenotrophomonas maltophilia (MW221274), with a negligible total P assimilation of 5.39 mg/pot. Whereas the addition of Pseudomonas agglomerans with PG gave outstanding total P absorption of 57.05 mg/pot when compared with PN input of 38.06 mg/pot. Finally, the results prove that the co-inoculation of Pseudomonas fluorescens with PG could be a promising and alternative option to use it as a source of P fertilizer for plants and to maintain a high level of nutrients in the soil.