Objective  Microencapsulation was applied to improve the stability of PGPRs for promoting corn growth.

  Method   Rhizosphere bacteria that promote corn growth were isolated. The bacteria in broth were encapsulated using sodium alginate (SA) and CaCl₂. Based on operation efficiency and PGPR survival rate, optimal conditions for the encapsulation were determined. Properties of the microencapsulated agent were analyzed for field applications with respect to the bacterial proliferation under varied artificial dehydration created by using polyethylene glycol (PEG) and salt, temperatures, pHs, and storage times as well as the growth and root morphology of the treated corn plants.

  Result  Two PGPR strains with multiple plant growth promoting functions were isolated. The microcapsule microbial agent prepared with a mass fraction of 1% SA-3% CaCl₂ had good stability. The embedding rate of the microcapsule microbial agent reached 91.27%, the number of live bacteria reached 8.73 × 10⁹ cfu·g⁻¹, and the proliferation was 7.79 times. Significant protection against the imposed adverse conditions was observed. In comparison with the virgin PGPRs broth, the encapsulation also significantly enhanced the growth of the treated corn plants with a 91.83% increase on plant height, 81.82% on seedling dry weight, and 29.57% on root dry weight over control. In addition, the total length, surface area, diameter, volume, and tip number of the roots of the corn plants grown with the encapsulated PGPRs were significantly increased as well.

  Conclusion  Microencapsulation significantly improved the stability as well as the root morphology and growth promoting effect of PGPRs on the corn plants.