Rock Phosphate Solubilization by Plant Growth-Promoting Bacillus velezensis and Its Impact on Wheat Growth and Yield

Application of phosphate solubilizing bacteria for improvement of existing pools of phosphate in soil is important for plant growth. From rain fed area of Mansehra, 14 microbes were isolated. Among these, three isolates Bacillus velezensis, Bacillus subtilis, and Bacillus safensis exhibited strong phosphate solubilizing potential, indole acetic acid (IAA) and organic acid production, and antibacterial and antibiotic resistances. Due to better phosphate solublization potential, plant growth-promoting rhizobacteria, B. velezensis was used as bio-inoculant on wheat var. Pir sabaq alone, with rock phosphate (RP) and with 50%, 75%, and 100% single super phosphate (SSP) and urea. Application of RP with B. velezensis increased 50% phosphate and nitrate in soil and 80% in leaves. Plants treated with 100% SSP + urea and B. velezensis showed 50% higher P in soil and 90% in leaves. Application with RP showed significant increases on growth indices of wheat and results were more pronounced in RP + B. velezensis and 100% SSP + urea + B. velezensis treatments. Soluble protein and sugar contents of leaves were 46% and 24% higher in RP + B. velezensis, while IAA and gibberellic acid (GA) were 34% and 54% higher. Highest increases in protein (56%), sugar (30%), IAA (50%), and GA (90%) were found in 100% SSP + urea + B. velezensis. Spike length, seeds per spike, and weight of 1000 seed were 19%, 32%, and 26% higher in RP + B. velezensis, while these increases were 39%, 52%, and 33%, respectively in 100% SSP + urea + B. velezensis treatment. Bio-inoculation of B. velezensis with RP and chemical fertilizer may be helpful for improving productivity of cereal crops and sustainable agriculture.