Co-application of lime and Ca-Mg-B-Zn-Fe amendment reduces root rot incidence and enhances tobacco growth in a field trial

Introduction Soil acidification increases the incidence of soil-borne diseases, especially tobacco root rot. Lime and related amendments are widely applied to mitigate soil acidification and crop diseases, whereas their growth-promoting and disease-suppressive mechanisms remain elusive. Methods Using field experiments and high-throughput sequencing, this study investigated the effects of lime-based amendments on acidification alleviation, rhizosphere microbiota reshaping and tobacco root rot suppression. The field trial set five treatments: control (CK), lime alone (C1), lime combined with seaweed extract (C2), lime combined with organic fertilizer (C3), and lime combined with commercial Ca-Mg-B-Zn-Fe amendment (C4). Soil properties, disease incidence, and the agronomic traits of tobacco were measured. Microbial community profiling and co-occurrence network analysis were employed to establish linkages between treatment-driven microbial variations and tobacco plant health. Results All treatments effectively alleviated acidification and reduced root rot incidence, with C4 showing the strongest efficacy, as evidenced by its increase in pH from 4.43-5.96 and reducing disease incidence by 62.05%. Lime-based amendments enriched beneficial taxa including Gemmatimonas , Pseudomonas , and Mortierella , while suppressing the relative abundance of potential pathogenic Setophoma by up to 80.77%. Network analysis showed that C4 treatment shifted genus Setophoma from module hubs to peripheral positions and enhanced microbial network stability. Discussion Collectively, lime combined with a Ca-Mg-B-Zn-Fe amendment was associated with alleviated soil acidification, lower root rot incidence, and a restructured rhizosphere community in which Setophoma declined and network topology shifted under C4. These field results identify a practical lime-based strategy for acidified tobacco soils.