Modulating effects of herbicide-safener co-application on rhizosphere microbiota and soil function in proso millet...

Mitigating herbicide-induced soil disturbances is critical for sustainable agriculture. Herbicide safeners protect crops without reducing weed control efficacy, yet their effects on rhizosphere health and microbial dynamics in proso millet systems remain unclear. This study investigated the impacts of monosulfuron (applied at 2.4 kg ha⁻¹) and gibberellin (GA₃, applied at 0.3 L ha⁻¹) on rhizosphere microbial communities and soil quality in China's semi-arid Loess Plateau. Field experiments compared herbicide (H), herbicide-safener (HS), manual weeding (MW), and control (CK) treatments. Results demonstrated that the H treatment caused evident phytotoxicity to proso millet, whereas the HS treatment effectively alleviated the monosulfuron-induced damage and increased grain yield by 28.39 % compared to the H treatment. Moreover, the HS treatment significantly enriched the relative abundance of Proteobacteria, reaching 29.27 %. Monosulfuron application reduced bacterial richness by 3.16-8.35 % and the Shannon diversity index by 0.82-7.48 % (7-70 DAS). Although the HS treatment increased AL-extractable P (AL-P) content at 7 DAS, it led to nutrient depletion and soil degradation by 70 DAS. Network analysis revealed that the H treatment enhanced negative bacterial interactions and simplified microbial co-occurrence networks (453 negative edges vs. 632 positive edges), yet increased network stability. In contrast, the HS treatment strengthened positive interactions (299 negative edges vs. 786 positive edges), improved system resilience, and stabilized key functional modules. Furthermore, the HS treatment shifted community assembly toward stochastic processes (contributing 86.41 %), reducing the role of environmental filtering. These results demonstrate that safeners mitigate herbicide-induced soil dysfunction by modulating stochastic assembly and microbial network structure, providing guidance for optimizing herbicide use in sustainable agriculture.