Response surface modeling and structural equation analysis reveal environmental and microbial drivers of pathogen suppression during Brassica biofumigation

BACKGROUND Biofumigation is increasingly recognized as an environmentally friendly strategy for controlling soil‐borne pathogens. However, its efficacy is highly dependent on environmental conditions, and practical predictive frameworks remain limited. A mechanistic understanding of how environmental factors interact with microbial communities and chemical metabolites is essential for optimizing biofumigation under field conditions. RESULTS Environmental factors significantly influenced biofumigation efficacy against Fusarium and Phytophthora . Strong interactive effects among temperature, soil moisture, and biofumigant dosage highlighted the necessity of synergistic multi‐factor management in practice. Among these, temperature emerged as the dominant regulator (partial η 2 = 0.92–0.96), acting as the primary driver that activates the suppressive pathways. Response surface modeling identified that an optimal balance for practical application was achieved at 41–43 °C, 17–19% soil moisture, and a moderate dosage of 4.76 g m −2 . Volatile organic compound (VOC) profiling identified dimethyl disulfide as a key bioactive component, while microbial analyses revealed the significant enrichment of disease‐suppressing taxa, particularly Paenibacillus . Structural equation modeling robustly explained 90% of the variance in suppression efficacy, revealing dual mechanistic pathways: temperature primarily drove pathogen inhibition via microbial regulation, whereas biofumigant dosage acted mainly through VOC‐mediated pathways. Additionally, high soil moisture negatively impacted both chemical accumulation and biological suppression. CONCLUSION Biofumigation efficacy is governed by a tightly coupled environmental–microbial–chemical framework. Rather than acting in isolation, high temperature, moderate moisture, and an optimized biofumigant dosage synergistically maximize pathogen suppression, providing actionable mechanistic insights and predictive guidelines for optimizing biofumigation in agricultural settings.