A new study reveals that biochar, a carbon rich material increasingly promoted for climate friendly agriculture, can have sharply different effects on greenhouse gas emissions depending on soil type and land use. The research shows that while biochar can significantly reduce nitrous oxide emissions in acidic upland soils, it may unexpectedly increase emissions in flooded rice paddies.
Nitrous oxide is one of the most potent greenhouse gases, with a warming effect far greater than carbon dioxide over the long term. Agricultural soils are a major source of these emissions, making mitigation strategies critical for climate and food system sustainability.
In the new study, researchers examined how biochar affects nitrous oxide production in two contrasting agricultural environments: acidic upland soils and flooded paddy soils. Using isotope analysis and microbial measurements, the team traced exactly which biological pathways were responsible for emissions.
The results showed that biochar reduced nitrous oxide emissions in acidic upland soils more effectively than lime treatments commonly used to adjust soil acidity. The reduction was linked to shifts in soil microbial activity. Biochar suppressed both bacterial and fungal processes that produce nitrous oxide while promoting genes associated with converting the gas into harmless nitrogen.
"Our findings suggest that biochar can help redirect microbial processes so that more nitrogen ends up as stable nitrogen gas rather than as a climate damaging emission," said one of the study authors. "This highlights the potential of biochar as a targeted mitigation strategy in certain agricultural systems."
However, the study also uncovered a contrasting outcome in flooded rice soils. In these waterlogged conditions, biochar stimulated several microbial pathways simultaneously, leading to a strong increase in nitrous oxide emissions. Instead of suppressing gas production, the added carbon and changes in soil chemistry appeared to energize microbial activity.
"This tells us that biochar is not a one size fits all solution," the authors explained. "Its climate benefits depend strongly on where and how it is applied."
The researchers emphasize that soil water conditions, organic matter content, and microbial communities all interact to determine how biochar influences nitrogen cycling. In upland soils, improved soil structure and carbon availability appeared to favor pathways that consume nitrous oxide. In contrast, flooded soils provided conditions where multiple nitrogen transformations intensified, amplifying emissions.
The study highlights the importance of understanding soil specific mechanisms before promoting large scale biochar use. Rather than assuming uniform benefits, the authors argue that climate mitigation strategies should be tailored to land use and soil type.
"By identifying the microbial pathways behind these emissions, we can begin to design smarter soil management practices," the researchers noted. "This knowledge helps us move toward agriculture that supports both productivity and climate goals."
The team concludes that future research should focus on field conditions, long term impacts, and practical application strategies. With better targeting, biochar could still play an important role in reducing agricultural greenhouse gases, but only when applied in the right context.
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Journal Reference: Chu C, Elrys AS, Dai S, Wen T, Xu J, et al. 2026. Biochar's contrasting effects on N2O emissions in acidic upland and flooded paddy soils. Nitrogen Cycling 2: e009 doi: 10.48130/nc-0025-0021
https://www.maxapress.com/article/doi/10.48130/nc-0025-0021
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Nitrogen Cycling (e-ISSN 3069-8111) is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.
