Plant growth promoting bacteria can be an alternative to increase plant production, and reduce production costs and environmental impacts. Ruminal bacteria have several abilities and some of them are related to plant growth promotion. The aim of this study is to evaluate the increase in maize and soybean plants and in soils promoted by the inoculation of three ruminal bacteria: Bacillus cereus, Lactobacillus acidophilus and Succinovibrio dextrinosolvens. The experiments were conducted in a complete randomized block design with five treatments and six replicates as follows: T1 = control; T2 = B. cereus, T3 = L. acidophilus, T4 = S. dextrinosolvens, T5 = B. cereus + L. acidophilus + S. dextrinosolvens. In vitro tests showed that bacteria were able to fix nitrogen, solubilize phosphorus, and synthesize indole acetic acid and amylase. S. dextrinosolvens increased the root dry matter of maize plants, L. acidophylus increased the phosphorus concentration in maize roots along with the mixture of the three bacteria and increased the shoot dry matter of soybean plants and also the phosphorus and nitrogen concentration in soybean plants. This is the first report showing that L. acidophilus and S. dextrinosolvens have great potential to be used as plant growth promoting agents.
Key words: Rhizobacteria, indoleacetic acid, nitrogen fixation, Zea mays, Glycine max.