Has compost with biochar applied during the process added value over biochar or compost for increasing soil quality in an arable cropping system?

Previous research showed that adding biochar at the onset of the composting process alleviates this process and reduces emissions. The objective of this study was to evaluate in a field trial whether this compost with biochar applied during the process (i.e., biochar-blended compost) has added value compared to compost or biochar alone on chemical, physical and biological soil properties and crop yield. A single application of biochar, compost and biochar-blended (BB) compost increased the C content of the top soil in the long term, but only compost and biochar-blended compost had a lasting effect on pH and the K content. Two to 4 years after a single application of all three amendments in the field, the soil microbial biomass, richness, diversity and community composition remained unchanged. Due to intensive soil tillage, biochar migrated to subsoil already after 2 growing seasons, thus increasing the C sequestration in subsoil. We conclude that in general, the biochar-blended compost outperformed biochar and had a similar effect as the compost. [Display omitted] •Soil quality was evaluated after adding biochar, compost and biochar-blended compost.•The products increased C content of the top soil for at least 4 years.•Biochar migrated to subsoil horizons due to intense soil tillage.•Biochar-blended compost had no added value over compost in the field.