Priestia megaterium ILBB592 based biofertilizer increases the efficiency of phosphorus fertilization, positively affects soybean nutrition and yield and modifies the rhizospheric bacterial community

Phosphorus (P) is needed by soybean plants to form vital molecules like ATP and nucleotides and perform plant functions like photosynthesis and Nitrogen biological fixation at nodules. Because P concentration in the soil solution is naturally low, P fertilization is applied to satisfy soybean requirements in high yielding crops. However, a small portion of added P is readily available to the plants, while most is retained by the soil matrix and eventually made available or lost through erosion and run-off to water bodies, where it promotes eutrophication. Therefore, technologies that enhance P uptake by crops could lead to lower P inputs and outputs from soybean cropping systems, improving sustainability. Priestia megaterium ILBB592 and Bacillus pumilus ILBB44 are two PGPR with P mobilization features that were single formulated as biofertilizers and co-inoculated with Bradyrhizobium elkanii on seeds of soybean Genesis 5602 in two consecutive years in the field, with and without P fertilization. Co-inoculation with ILBB592 improved plant P uptake, along with N and K, with and without P fertilization. Diversity was increased by co-inoculation with ILBB44 and ILBB592, and predicted genes related with P cycling in the rhizospheric soils were also augmented after co-inoculation with ILBB592, mostly with P fertilization. Shoot dry weight and yield were also improved although effect on yield was not statistically significant. P fertilization alone had no effect in the first year but showed some effect on nodules dry weight, P uptake and yield on the second year, suggesting a sufficient P level was obtained after repeated fertilizations. ILBB592 biofertilizer showed a positive effect on most plant parameters, including nodulation and P uptake in both years and both P fertilization regimes and is therefore considered as a useful technology to reduce P fertilization without jeopardizing plant performance.