Assessment of phosphate-solubilizing rhizobacterial strains combined with rock phosphate and compost and their effect on the growth and yield of maize (Zea mays L.) under field conditions

Adequate phosphorus (P) supply is critical for optimum plant growth. However, soils enriched in total P content frequently do not fulfill the plant requirements due to the provided P, which may become unavailable in alkaline calcareous soils. The use of slow-release P fertilizers, such as rock phosphate (RP), compost, and plant growth-promoting rhizobacteria (PGPR) with P-solubilizing activity, can stimulate plant growth by solubilizing inaccessible P in the soil. A field study was conducted to estimate the efficacy of PGPR containing P-solubilizing and ACC-deaminase activity in soil amended with RP and compost on the production and growth of maize. Ten pre-isolated bacterial isolates were taken and tested for their effect on maize with individual and combined application of PSB, RP, and compost with a control. Overall, bacterial isolates (S5 and S6) containing P-solubilizing and ACC-deaminase activity combined with RP and compost significantly improved the maize crop development and production over the control. Finally, it is suggested that RP could be efficiently applied combined with compost and P-solubilizers.