Response of maize to seed priming with seaweed extracts and plant growth promoting rhizobacteria

Plant growth-promoting rhizobacteria (PGPR) and seaweed extracts (SWE) individually improve crop performances, but the response of crops upon their combined use is less understood. A field experiment on maize was carried out to evaluate the effect of seed priming with PGPR and undiluted SWE on the growth, yield, and nutritional quality of maize and soil properties. A split-plot design comprising 15 treatment combinations was laid out with SWE as the main factor (no SWE, Kappaphycus alvarezii and Sargassum cinctum extract, and PGPR as sub-plot factor (no PGPR, Bacillus megaterium, B. subtilis, Paenibacillus polymyxa and Azotobacter chroococcum). The composition and properties of SWE and PGPR were assessed. Without SWE, seed priming with all PGPR enhanced cob yield, the maximum improvement (32%) over no PGPR being recorded with A. chroococcum treatment. However, SWE priming along with PGPRs had no additional yield advantage compared to PGPR used alone. In the presence of either SWEs, A. chroococcum treatment was superior to other PGPR for most of the crop parameters like yield, carbohydrates and micro-nutrients in grains. The higher nutrient uptake agreed well with soil nutrient status after harvest. There were no deleterious effects on any parameters due to co-priming with K. alvarezii or S. cinctum extract with A. chroococcum, which was not the case with B. subtilis treatment where there was a significant decrease in growth and yield parameters despite evidence of increasing bacterial colony count. The study suggests the need for assessing optimal SWE doses for combinatorial PGPR treatments.