Biochar boosts carbon storage in paddy soils by changing microbial communities, study finds

A new study in the journal Biochar shows that converting rice straw into biochar before adding it to paddy soils can dramatically increase carbon storage. Researchers found that biochar increased soil organic carbon by 103% compared to untreated soil, while raw straw only increased it by 38.7%. The key difference is that biochar promotes slow-growing microbes that build stable mineral-associated organic carbon, whereas straw feeds fast-growing microbes that release more CO2 and break down existing soil carbon. The 65-day incubation experiment used carbon-13 labeled materials to trace exactly where the added carbon went. Biochar achieved a carbon sequestration efficiency of 99.7%, meaning almost all the carbon stayed in the soil. Straw only retained 22.8% of its carbon. The findings suggest that converting some crop residues into biochar before returning them to fields could be a practical strategy for climate-smart agriculture in rice-growing regions.