The use of bioinoculants aligns with ecological intensification in agriculture, but their effects on crop performance and soil microbiota under different fertilization regimes remain unclear. This study evaluated the impact of a bioinoculant containing two phosphate-solubilizing bacterial strains (Priestia megaterium and Bacillus subtilis) on maize yield, root architecture, and rhizosphere microbial communities via seed inoculation in a clayey soil. Maize was cultivated for two consecutive seasons under treatments combining inoculation, phosphorus sources (triple superphosphate or reactive rock phosphate), and P doses (0 or 120 kg ha⁻¹ of P₂O₅). Root traits, phosphatase activities, and microbial diversity were assessed at flowering, while agronomic parameters and nutrient content were measured at harvest. In the first season, microbial alpha diversity was higher, accompanied by a 31.5% increase in root surface area and a 46.2% increase in P-resin availability. In contrast, the second season showed greater phosphatase activity and higher grain P and K concentrations, by 42.3% and 38.2%, respectively. Grain yield did not differ significantly between inoculated and non-inoculated treatments; however, root, plant, and microbial traits varied markedly across seasons. Principal component analysis revealed that productivity was primarily driven by seasonal variation rather than by fertilization or inoculation. These findings emphasize that the effectiveness of bioinoculants and P fertilization, as well as their influence on the microbiota, are highly context-dependent, being shaped by environmental conditions, soil nutrient availability, and crop genotype.

Phosphorus (P) limitation constrains crop production in highly weathered tropical soils, and microbial inoculants may enhance P acquisition, although their effectiveness varies with edaphic conditions. We hypothesized that the effects of a phosphate-solubilizing bacterial inoculant on plant performance and belowground processes would depend on soil P status and no-tillage history. A two-year field experiment on an Oxisol in the Brazilian Cerrado (Chapadão do Sul, MS, Brazil) compared newly established, low-P (NTS-NC) and consolidated, high-P (NTS-C) no-tillage systems. Treatments combined 0, 50, or 100% of recommended P fertilization with or without BiomaPhos^®, composed of Priestia megaterium CNPMS B119 and Bacillus subtilis CNPMS B2084. Grain yield, resin-extractable soil phosphorus (P-resin), root architecture, bacterial and arbuscular mycorrhizal fungal (AMF) communities, AMF colonization, and phosphatase activities were evaluated. Grain yield in NTS-C exceeded NTS-NC by 15.7% and 18.8% in 2021/2022 and 2022/2023, respectively. Inoculation × P interactions for yield and P-resin occurred only in NTS-NC in the second season. Inoculation altered root architecture, whereas P availability reorganized bacterial association networks. AMF responses were limited and season-specific, while inoculation reduced AMF colonization and phosphatase activity primarily in NTS-C. These findings confirm that inoculant performance is context-dependent and should be integrated with site-specific P fertilization strategies.

Anais do Congresso Brasileiro Interdisciplinar em Ciência e Tecnologia (2764-0582) - Geração De Biogás A Partir Da Biomassa Do Malte Da Fabricação De Cervejas Artesanais