Inoculation of cold-adapted microbial consortium screened from alpine meadows promotes the growth of mixed grasses by changing soil properties and enzyme activity

The objective of this study was to investigate the effect of co-inoculation of three PGPR strains and inoculation ratio on the growth characteristics and soil properties of mixed grasses. In this study, we used 3 strains of PGPR for the material, which were Acinetobacter calcoaceticus called HMAJ1, Pseudomonas piscium called HMAJ5, and Pseudarthrobacter psychrotolerans called NCZ1, with nitrogen fixation and phosphorus solubilization ability. By mixing the bacteria in a different ratio, the effect of inoculating with a microbial consortium on the plant and soil properties of mixed grasses (Elymus nutans Griseb, Festuca sinensis, and Poa pratensis L.) was evaluated and the best microbial inoculants ratio was selected. The results showed that inoculating with a microbial consortium increased the soil organic carbon , available phosphorus, ammonium and nitrate nitrogen content, and the activities of soil alkaline phosphatase, sucrase, peroxidase, and urease, which promoted the plant height and biomass of mixed grasses. Pearson correlation analysis showed that plant characteristics were differently correlated with soil properties. Grey correlation analysis of plant biomass, soil properties, and soil enzyme activity revealed that T7 (HMAJ1:NCZ1 = 3:7) was the most effective in improving mixed-grasses biomass and soil quality. Our results indicated that the positive interaction of nitrogen-fixing bacteria with phosphorus-solubilizing strains may become a novel and effective bio-inoculant to achieve sustainable pulse productivity.