Assessment of Shelf-life and Efficacy of the Seed-Coating Delivery System of Biofertilizers in Maize

Film-coating of seeds is a widely accepted technology in agriculture for effectively protecting germinating seeds and seedlings against biotic and abiotic stresses and successfully delivering agro-chemicals, biomolecules, and bio-inoculants to the rhizosphere region. The present experiments explored the possibility of using hydroxypropyl methylcellulose (HPMC) and dextrin as film-coating agents for impregnating maize seed with four different biofertilizer strains. Azospirillum brasilense (Sp7), Bacillus megaterium var phosphaticum (Pb1), Paenibacillus mucilaginosus (KRB9), and Pseudomonas chlororaphis (ZSB15) were prepared as consortium containing an equimolar ratio of each strain. The in vitro growth experiment revealed that HPMC, dextrin, or a combination of both did not affect the growth of all four biofertilizers. When biofertilizer consortium was film-coated on maize seed using HPMC and dextrin as film-coating /binding and protecting agents, no apparent changes were observed in the size, shape, weight, and volume of maize seeds. The shelf-life study on film-coated maize seeds revealed that the microbial inoculants accounted for a one-log reduction (from 104 cells at initial to 103 cells after 3 months) when stored at low temperature. The pre-coated seeds with microbial-inoculants showed significant improvement in seedling growth. Hence, the film-coating of maize seed with microbial inoculants using HPMC and dextrin could be an effective delivery system for ensuring rhizosphere colonization of biofertilizers for sustainable maize cultivation.