The impact of chemical fertilization on rhizosphere soil communities is a growing concern due to the changes they cause on microbes in soil ecosystems. The present study aims to compare mycorrhizal inoculation and fertilizer applications on bacterial and fungal communities in rhizosphere soil of intensively cultivated Robinia pseudoacacia and Populus × euramericana plantations using the Illumina Miseq sequencing platform. Our results revealed that the different host plants and applied treatments did not significantly affect soil bacterial diversity, but interfered with native rhizosphere bacterial communities in plantation sites. In contrast, host plants and inorganic fertilizer had a strong effect at the family and genus level on the composition of soil fungal communities. In conclusion, our findings suggest that the structure and composition of the fungal community are more sensitive to the nutrient sources in soil than bacteria.

Optimizing nutrient management in organic polytunnel production remains challenging due to the limited availability of field-based knowledge on the mineralization dynamics of organic fertilizers. At the same time, microalgae-based products such as Chlorella vulgaris have gained increasing attention in recent research, yet their interactions with nutrient supply intensity are not well understood. This study aimed to evaluate the effects of increasing nutrient supply intensities (34, 116, and 189 kg ha⁻¹ N from different organic sources), in combination with C. vulgaris foliar application, on the crop performance of kapia pepper and a subsequent leafy green crop under on-farm organic polytunnel conditions on soil with moderate organic matter content. Increasing production intensity did not result in significant improvements in pepper yield or vegetative biomass (p > 0.05), and no significant residual effects of nutrient supply were detected in the yield of the subsequent leafy green crop (p: 0.08–0.94). C. vulgaris treatment showed predominantly non-significant but positive trends in several parameters, but only in combination with high-intensity technology, while reducing the total pest damage of the thrips and stinkbug index up to 15.7% in most technology variations. These results indicate that the effects of C. vulgaris may be strongly context-dependent and confirm that increasing the intensity of nutrient supply may carry the risks of conventionalization of organic farming practices.

Arbuscular mycorrhizal fungi (AMF) are widely applied as bioinoculants to enhance crop performance, yet their broader ecological effects on rhizosphere microbial assembly under field conditions remain insufficiently understood. Here, we evaluated the impact of a commercial AMF inoculant and its carrier material on lettuce performance and rhizosphere microbial communities in an open-field experiment. We hypothesized that both viable AMF propagules and formulation components contribute to shifts in rhizosphere processes. Active AMF inoculation significantly increased root colonization and fresh biomass at harvest, confirming successful establishment and enhanced plant performance under field conditions. Colonization levels in the heat-inactivated carrier treatment were comparable to the non-inoculated control, indicating that the carrier did not inhibit indigenous AMF activity or induce nutrient-mediated suppression of symbiosis. Plant physiological responses were stage-dependent, supporting the context-dependent nature of AMF effects in dynamic field environments. High-throughput sequencing revealed no significant treatment effects on bacterial or fungal alpha diversity. However, beta-diversity analyses demonstrated significant compositional restructuring of rhizosphere communities, particularly within the bacterial domain. A stable core microbiome persisted across treatments, yet relative abundances and community evenness were altered by both active inoculation and carrier application. These results suggest that AMF inoculation reorganizes microbial community structure predominantly via shifts in ecological niche occupation. Collectively, our results show that AMF inoculation functions not only as a symbiotic nutrient-acquisition strategy but also as a driver of rhizosphere microbial reorganization under field conditions. Integrating plant performance with microbiome dynamics provides a more comprehensive framework for understanding and optimizing microbial inoculants in sustainable agricultural systems.