Effect of PGPRs on the Rhizosphere Microbial Community Structure and Yield of Silage Maize in Saline–Alkaline Fields

Plant Growth Promoting Rhizobacteria, PGPR, can protect plants against soil-borne diseases and abiotic stress conditions. The primary objective of this study was to evaluate the effects of different PGPRs (TF1, TF2, TF3, and TF4) on the rhizosphere microbial community of silage maize in a saline-alkaline field via Illumina MiSeq high-throughput sequencing technology. Results demonstrated that different PGPRs significantly increased the harvest density (by 21.31-45.16%), plant height (by 9.12-19.98%), stem diameter (by 30.07-45.78%), and biomass (by 33.20-65.36%) of silage maize, TF3 treatment significantly increased the fresh weight (by 32.50%), while the other treatments could increase the fresh weight but not significantly. Four microbial agents significantly reduced the contents of soil available phosphorus (AP), electrical conductivity (EC), and neutral phosphatase activity (NPA), while significantly increasing the contents of available potassium (AK), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), chitinase activity (ChtA), and urease activity (UA). Specifically, TF2 and TF3 treatments significantly decreased the soil pH value, while not for TF1 and TF4. Microbiome analysis showed that four microbial agents significantly increased the relative abundances of beneficial microorganisms, such as <i>Arthrobacter</i>, <i>Blastococcus</i>, <i>MNDI</i>, <i>Chaetomidium</i>, <i>Alternaria</i>, <i>Sarocladium</i>, <i>Acremonium</i>, and <i>Clonostachys</i>, and significantly decreased the relative abundances of <i>Gibberella</i> and <i>Fusarium</i>. Mental analysis showed that the soil bacterial community structure did not significantly correlate with soil biochemical properties, while the soil fungal community structure significantly and positively correlated with pH. Maize yield significantly and positively correlated with NH₄⁺-N, OM, AP, EC, UA, ChtA, and NPA.