Impact of plant growth-promoting bacteria on grain yield, protein content, and urea-15 N recovery by maize in a Cerrado Oxisol

The inoculation of cereal crops with plant growth-promoting bacteria (PGPB) is a potential strategy to improve fertilizer-N acquisition by crops in soils with low capacity to supply N. A study was conducted to assess the impact of three inoculants on grain yield, protein content, and urea-(15) N recovery in maize (Zea mays L.) under Cerrado soil and climate conditions. The main treatments included inoculants containing (i) Azospirillum brasilense strain Sp245, (ii) A. brasilense strains AbV5 + AbV6, (iii) Herbaspirillum seropedicae strain ZAE94, and (iv) a non-inoculated control. The subtreatments were (i) urea-N fertilization (100 kg N ha(-1)) at 30 days after sowing and (ii) no N addition at the stage. To determine fertilizer-N recovery, N-15-labelled urea was applied in microplots. Inoculants carrying A. brasilense improved urea-(15) N acquisition efficiency in maize and also improved grain yield compared to the non-inoculated control, while urea-N fertilization enhanced grain quality by providing higher protein content. Our results suggest that the inoculation of maize grains with PGPB represents a strategy to improve fertilizer-N recovery and maize yield in Cerrado soil with a low capacity to supply N.