Soil acidification is a growing threat to food production, especially in intensively managed agricultural regions where repeated fertilizer use can gradually make soils more acidic, reduce nutrient availability, and increase the mobility of toxic metals. A new five-year field study published in Biochar shows that biochar may do more than simply neutralize acidic soils. It can help organize a coordinated recovery process across the entire soil ecosystem.
The study, titled “Biochar orchestrates coordinated soil-microbe-metabolite responses in acidifying paddy soils: evidence from a 5-year field study,” compared biochar with two commonly used soil amendments, lime and swine manure, in an acidic paddy field in Zhejiang Province, China. The research team applied biochar at three rates, along with lime and manure treatments, and then used advanced multi-omics tools to examine changes in soil chemistry, microbial communities, viral communities, gene functions, and soil metabolites.
“Our findings show that biochar does not act only as a chemical amendment,” said corresponding author Huaihai Chen. “It appears to initiate a step-by-step ecological cascade, beginning with improved soil conditions and extending to microbial functions and metabolite production that are important for long-term soil health.”
Across treatments, soil amendments helped reduce acidification, with soil pH increasing from about 5.5 to 6.4 and exchangeable aluminum dropping sharply from 12.5 to 3.5 mg kg−1. However, the strongest and most coordinated responses occurred under high-dose biochar treatment. Compared with lime and manure, biochar produced broader changes that linked improved soil chemistry with biological and metabolic recovery.
The researchers found that high-dose biochar improved soil organic matter, cation exchange capacity, and nutrient availability while reducing the bioavailability of metals such as aluminum, cadmium, iron, and nickel. These chemical improvements were associated with shifts in prokaryotic and viral communities. Biochar enriched microbial groups such as Chloroflexi and Planctomycetota, which are often linked with nutrient cycling, and also influenced viral groups including Algavirales and Crassvirales.
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