Background The interaction of biochar with beneficial microorganisms and its role as a plant disease suppressor has garnered significant research interest, yet these roles in activated or oxidized biochars remain insufficiently explored. This study investigated three activated biochars derived from the same wood-based biochar: biochar treated with hydrogen peroxide (H2O2-biochar), biochar treated with nitric acid (HNO3-biochar), and biochar treated with elemental sulfur and chitin (biochar + S + chitin), produced by incubating the raw biochar with elemental S and chitin. To evaluate the fungal carrier capacity, activated biochars were inoculated with a plant-beneficial fungus (Trichoderma asperellum), and population growth was measured using colony-forming unit (CFU) counts. Plant disease suppressive capacity was assessed by measuring leaf area and root development in cress plants inoculated with the plant pathogen Globisporangium ultimum. Results First, the inoculation of activated biochars with T. asperellum showed that the H2O2 treatment significantly boosted its microbial carrier capacity (4.99 × 106 CFU g−1 biochar) as compared to untreated or HNO3-biochar which reached up to 1.03 × 106 CFU g−1 biochar. Second, we studied the application of chitin, an organic fertilizer, to activate the biochar biologically and increase its N content. The addition of chitin to biochar increased the microbial activity when using H2O2-biochar or combining biochar with S, as observed by the increase in either sulfate, nitrate, or electrical conductivity. When added to the growing media for cress cultivation, H2O2-biochar incubated with chitin demonstrated disease suppression against G. ultimum. Chitin also notably increased the mineral N concentration of biochar’s blend, particularly when combined with S, with concentrations reaching 835 mg mineral N L−1 biochar after 12 weeks of incubation. Conclusions Activated biochar with H2O2 demonstrated effective plant growth-promoting fungi carrier capacity. The combination of elemental S and chitin not only enhanced the suppressive potential of biochar, but also showed promise for the development of biochar-based N fertilizers. Graphical abstract

Chemically and biologically activated biochars as potential inoculant carriers, biofertilizers or plant disease suppressors

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2025年6月16日

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Raúl Castejón-del Pino,
Jane Debode,
Miguel Angel Sánchez-Monedero,
María Luz Cayuela,
Bart Vandecasteele

摘要

Background

The interaction of biochar with beneficial microorganisms and its role as a plant disease suppressor has garnered significant research interest, yet these roles in activated or oxidized biochars remain insufficiently explored. This study investigated three activated biochars derived from the same wood-based biochar: biochar treated with hydrogen peroxide (H₂O₂-biochar), biochar treated with nitric acid (HNO₃-biochar), and biochar treated with elemental sulfur and chitin (biochar + S + chitin), produced by incubating the raw biochar with elemental S and chitin. To evaluate the fungal carrier capacity, activated biochars were inoculated with a plant-beneficial fungus (Trichoderma asperellum), and population growth was measured using colony-forming unit (CFU) counts. Plant disease suppressive capacity was assessed by measuring leaf area and root development in cress plants inoculated with the plant pathogen Globisporangium ultimum.

Results

First, the inoculation of activated biochars with T. asperellum showed that the H₂O₂ treatment significantly boosted its microbial carrier capacity (4.99 × 10⁶ CFU g⁻¹ biochar) as compared to untreated or HNO₃-biochar which reached up to 1.03 × 10⁶ CFU g⁻¹ biochar. Second, we studied the application of chitin, an organic fertilizer, to activate the biochar biologically and increase its N content. The addition of chitin to biochar increased the microbial activity when using H₂O₂-biochar or combining biochar with S, as observed by the increase in either sulfate, nitrate, or electrical conductivity. When added to the growing media for cress cultivation, H₂O₂-biochar incubated with chitin demonstrated disease suppression against G. ultimum. Chitin also notably increased the mineral N concentration of biochar’s blend, particularly when combined with S, with concentrations reaching 835 mg mineral N L⁻¹ biochar after 12 weeks of incubation.

Conclusions

Activated biochar with H₂O₂ demonstrated effective plant growth-promoting fungi carrier capacity. The combination of elemental S and chitin not only enhanced the suppressive potential of biochar, but also showed promise for the development of biochar-based N fertilizers.

Graphical abstract