Synergistic effect of biochar on biological control measures for suppressing soil-borne diseases: A review

As a critical factor affecting global food security, soil-borne diseases constrain the sustainable agricultural development worldwide. Biological control methods, including the application of biocontrol agents (BCAs), phage therapy, and organic fertilizers, provide relatively eco-friendly solutions for enhancing soil ecosystem health. Biochar (BC) has recently gained increasing attention as a promising amendment for soil-borne diseases suppression. Although BC does not directly kill pathogens, its alkaline nature and strong adsorption capacity help modulate soil conditions to curb disease incidence indirectly. However, the diversity of soil-borne pathogens and the complexity of pathogenic mechanisms make single-method strategies insufficient for achieving stable and effective control. In this review, the synergistic mechanisms of BC in enhancing biological control measures for suppressing soil-borne diseases were systematically analyzed. When combined with BCAs, BC can enhance soil microbial community resistance, adsorb and neutralize root exudates, and upregulate plant expression of defense-associated genes. For phage therapy, BC improves phage-specific infection efficiency by modifying the soil microenvironment, intensifies survival pressure on pathogens, and simultaneously suppresses antibiotic resistance genes (ARGs) transfer. Furthermore, BC synergizes with organic fertilizers to improve the nutrient availability for beneficial microbes and reshape rhizosphere microbial communities. Additionally, this review systematically evaluates factors influencing the efficacy of BC-based biocontrol strategies and proposes applicable approaches for their joint use, including the optimization of process parameters (e.g., feedstock and pyrolysis conditions) and the screening of suitable BCAs or phages. This review offers valuable insights for developing integrated BC-biocontrol frameworks, providing a sustainable approach to enhancing soil health and agricultural productivity.