ABSTRACT The impact of Bacillus firmus –based bionematicides on rhizosphere microbiota and plant performance remains poorly understood in complex agroecosystems. This study evaluated the effects of B. firmus application on soil microbial communities, nematode dynamics, and soybean productivity in the Pampa biome. Our results demonstrate that B. firmus significantly modulates the composition and diversity of soil microbiota, with effects varying across locations and over time. Treated areas exhibited shifts in bacterial communities, including increased abundance of beneficial taxa, while fungal diversity tended to decrease, likely due to the combined effect of the fungicide used in seed treatment. Despite persistent populations of target nematodes such as Pratylenchus brachyurus and Heterodera glycines , treated areas showed reduced root infestation in specific stages and locations. Importantly, the application of B. firmus consistently enhanced soybean shoot and root growth, resulting in productivity gains of 6%–7% across all sites. These findings reveal that B. firmus not only contributes to plant growth promotion but also induces significant, yet context‐dependent, shifts in rhizosphere microbial communities. The study highlights the ecological complexity of microbial responses to biocontrol agents and underscores the importance of integrating microbiome dynamics into sustainable nematode management strategies in agroecosystems.
Fagundes et al. (2026) studied this question.