Plant growth-promoting bacteria improve maize growth through reshaping the rhizobacterial community in low-nitrogen and low-phosphorus soil

The effects of 13 plant growth-promoting rhizobacteria (PGPR) from the maize rhizosphere and a model PGPR strain Azospirillum brasilense Az39 on maize growth were monitored in a 3-year field inoculation experiment (from 2018 to 2020) with low-nitrogen (N) (N input reduced by 50%) and low-phosphorus (P) (no P supply) soils in Northeast China. The effects of four efficient PGPR that stably promoted maize plant growth and affected on the composition and function of the rhizobacterial community were further investigated in 2019 and 2020. On average, Sinorhizobium sp. A15, Bacillus sp. A28, Sphingomonas sp. A55, and Enterobacter sp. P24 stably increased grain yield by 8.1-17.8% and 11.0-20.1% in low-N and low-P soil, respectively. Inoculation of these four strains increased the abundance and species richness of rhizobacteria, enriched special beneficial bacteria such as Chloroflexia_KD4-96 and Bacilli, and decreased bacterial functions related to soil-N loss. We conclude that some PGPR can N- and P-use efficiency and maize yield through reshaping the rhizobacterial community.