Biochar and Bacillus velezensis: Interactive Effects on Soil and Wheat Yield

Agricultural intensification has progressively degraded soil quality, highlighting the need for sustainable amendments that simultaneously enhance soil chemical and biological properties while supporting crop productivity. In this study, we evaluated the effects of two poultry-manure-derived biochars, produced at 500 °C (BC500) and 700 °C (BC700), inoculated or not with Bacillus velezensis, on soil chemical and enzymatic properties, microbial diversity and structure, and wheat (Triticum aestivum) yield. Both biochars increased soil pH, organic matter, total C, total N, and cation exchange capacity. BC500 was associated with higher extractable phosphorus and ß-glucosidase activity, whereas BC700 promoted greater xylosidase and phosphomonoesterase activities. Inoculation with B. velezensis enhanced microbial diversity and evenness, as well as ß-glucosidase activity. Regarding crop performance, BC500 improved yield compared with BC700, which reduced shoot biomass and grain production. Multivariate analyses revealed strong associations between soil chemical and enzymatic properties and microbial community structure, although these relationships did not always translate into improved wheat yield. Overall, our findings highlight that the effects of biochar depend on its type and its interaction with PGPR, which must be considered in the design of sustainable agricultural management strategies.