Biochar and hydrochar show contrasting climate effects in boreal grasslands
New study reveals that different types of char can raise or lower greenhouse gas emissions from northern soils
Biochar Editorial Office, Shenyang Agricultural University
image:
Effects of biochar, hydrochar and nitrogen fertilization on greenhouse gas fluxes, soil organic carbon pools, and biomass yield of a boreal legume grassland
view moreCredit: Hem Raj Bhattarai, Ella Honkanen, Hanna Ruhanen, Helena Soinnie, Jenie Gil, Summaira Saghir, Reijo Lappalainen & Narasinha J. Shurpali
Adding carbon-rich materials such as biochar and hydrochar to farmland soils is often seen as a promising way to fight climate change. But a new study from Finland shows that the type of char used can make a big difference in whether the soil releases or stores greenhouse gases.
Researchers from the Natural Resources Institute Finland (Luke) and collaborating universities tested how biochar and hydrochar, combined with nitrogen fertilizer, affected greenhouse gas emissions, soil carbon pools, and crop yield in a typical boreal legume grassland. Over a three-month experiment, they measured emissions of carbon dioxide, nitrous oxide, and methane from soils growing timothy grass and red clover.
The team found that biochar and hydrochar influenced soil processes in opposite ways. Biochar, produced by high-temperature pyrolysis of birch wood, tended to increase nitrous oxide emissions, a potent greenhouse gas linked to fertilizer use. In contrast, hydrochar, made by lower-temperature hydrothermal carbonization of birch bark, suppressed nitrous oxide release and in some cases even turned the soil into a small nitrous oxide sink.
“These findings show that not all chars behave the same way,” said lead author Hem Raj Bhattarai of Luke. “Hydrochar appears to promote soil processes that remove nitrous oxide, while biochar can stimulate microbial activity that produces it.”
Both char types significantly increased the amount of particulate organic carbon in the soil, helping to build up organic matter. However, they had little effect on total carbon dioxide and methane fluxes or on the overall biomass yield of the grass-clover mixture. Interestingly, biochar with nitrogen fertilizer slightly reduced the yield of timothy grass, suggesting that it might limit nitrogen uptake in some conditions.
The study also found that hydrochar supported higher microbial biomass carbon than biochar, indicating a more active soil microbial community. This difference, the researchers say, may help explain why hydrochar reduced nitrous oxide emissions.
“Our results highlight the complex interactions among soil microbes, vegetation, and nitrogen management,” Bhattarai said. “Selecting the right char type for a specific soil and crop system is essential if we want to use these materials to improve soil health and mitigate greenhouse gas emissions.”
The authors suggest that future studies should examine char effects at the field scale and across different soil types to better guide sustainable agriculture in northern regions.
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Journal Reference: Bhattarai, H.R., Honkanen, E., Ruhanen, H. et al. Effects of biochar, hydrochar and nitrogen fertilization on greenhouse gas fluxes, soil organic carbon pools, and biomass yield of a boreal legume grassland. Biochar 7, 114 (2025). https://doi.org/10.1007/s42773-025-00496-6
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About Biochar
Biochar is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
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Journal
Biochar
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Effects of biochar, hydrochar and nitrogen fertilization on greenhouse gas fluxes, soil organic carbon pools, and biomass yield of a boreal legume grassland
Article Publication Date
28-Sep-2025
Roots in the dark: Russian scientists uncover hidden carbon dioxide uptake in plant roots
Groundbreaking model experiment led by Dr. Amiran Khabidovich Zanilov at Kabardino-Balkarian State University reveals how light, fertilizer, and CO₂ levels shape plant carbon nutrition—challenging long-held assumptions in plant biology
Biochar Editorial Office, Shenyang Agricultural University
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Influence of external factors on the behavior of CO2 in the root system of plants in a model experiment
view moreCredit: Zalim Islamovich Dudarov, Amiran Khabidovich Zanilov, Yuri Kambulatovich Altudov & Yuri Khasanovich Shogenov
We’ve all learned the same story in school: plants breathe in carbon dioxide (CO₂) through their leaves during photosynthesis, and breathe it out through respiration. The roots? They’re just for water and nutrients, right?
Think again.
In a surprising twist to one of biology’s most fundamental processes, a new study published on October 17, 2025, in the open-access journal Carbon Research has revealed that plant roots can actively absorb CO₂ from the soil—and this hidden process is powerfully influenced by light, fertilizer, and atmospheric conditions.
Led by Dr. Amiran Khabidovich Zanilov at the Center for Decarbonization of the Agro-Industrial Complex and Regional Economy, Kabardino-Balkarian State University Named After H.M. Berbekov, this innovative model experiment is rewriting the textbook on how plants feed themselves—and offering fresh insights into the global carbon cycle.
A New Window into Plant Breathing
To crack the mystery of root-level CO₂ dynamics, Dr. Zanilov and his team designed a custom experimental system with hermetically sealed chambers for both leaves and roots, equipped with high-precision CO₂ sensors. This allowed them to track CO₂ fluxes in real time across the entire soil–plant–atmosphere continuum—a rare feat in plant physiology research.
Using 19 maize plants over a 40-day period, they tested four distinct environmental scenarios, each designed to mimic real-world changes in farming and climate.
Light Switches On a Hidden Root Mechanism
In Mode A, the team explored how day-night cycles affect CO₂ exchange. What they found was striking: as daylight ended and photosynthesis paused, CO₂ concentrations in the leaf chamber rose, while those in the root chamber dropped sharply—revealing an inverse correlation (r = -0.859).
This means that when leaves stop absorbing CO₂, roots kick in, potentially scavenging carbon directly from the soil air. Even more fascinating: root CO₂ uptake peaked during daylight when atmospheric CO₂ reached 367–417 ppm—levels eerily close to today’s real-world concentrations.
“This suggests that root-based CO₂ absorption isn’t just a curiosity—it may be an alternative carbon nutrition pathway,” says Dr. Amiran Khabidovich Zanilov. “When light is abundant, roots might help buffer or supplement carbon supply, especially under fluctuating atmospheric conditions.”
Fertilizer’s Double-Edged Effect
In Mode B, the researchers introduced ammonium nitrate fertilizer—a common practice in modern agriculture. But instead of boosting carbon uptake, the results showed a short-term setback: leaf respiration increased at night, and daytime CO₂ absorption dropped significantly, from 70.4 ppm to 92.3 ppm compared to unfertilized plants.
“The nitrogen boost comes at a cost,” explains Dr. Zanilov. “It appears to shift the plant’s energy balance, increasing metabolic activity but temporarily reducing its ability to fix carbon during the day. Farmers may need to consider timing and dosage to avoid undermining photosynthetic efficiency.”
Brighter Light, Slower Shutdown
Mode C tested how light intensity affects plant behavior. When illumination doubled—from 1750 to 3500 lux—something unexpected happened after lights-out: the leaves didn’t start respiring immediately. Instead, there was an 80-minute delay before CO₂ began to rise in the leaf chamber.
This lag suggests that high-light-grown plants store more energy or carbon intermediates, allowing them to maintain internal balance longer once photosynthesis stops. It’s like a battery charge that keeps the lights on a little longer after sunset.
When the Air Gets Thick: Roots Shut Down
Finally, in Mode D, the team simulated rising CO₂ levels—such as those caused by intense soil microbial activity or climate change. As CO₂ in the leaf chamber climbed from 500 to 1500 ppm, something dramatic occurred: root CO₂ absorption stopped completely.
At high atmospheric CO₂, the concentration gradient reverses, making it harder for roots to take up gas from the soil. This could mean that in a future high-CO₂ world, this newly discovered root carbon pathway may become less effective—unless plants adapt.
Why This Changes Everything
For decades, scientists assumed that plant roots were net producers of CO₂ through respiration, not consumers. This study challenges that view, showing that under normal conditions, roots can act as carbon sinks, not just sources.
These findings have profound implications:
- For climate models, which must now account for potential root-level CO₂ uptake in terrestrial carbon budgets.
- For agriculture, where optimizing light, fertilizer, and soil conditions could enhance carbon capture and crop resilience.
- For ecology, as we rethink how plants interact with soil carbon in forests, wetlands, and croplands.
Spotlight on Kabardino-Balkarian State University
At the heart of this discovery is the Center for Decarbonization of the Agro-Industrial Complex and Regional Economy at Kabardino-Balkarian State University Named After H.M. Berbekov in Nalchik, Russia. Under Dr. Zanilov’s leadership, this regional research hub is emerging as a leader in innovative carbon science, combining engineering ingenuity with ecological insight to tackle global challenges from the ground up.
“This work shows that breakthroughs don’t always come from big cities or well-funded labs,” says Dr. Zanilov. “Sometimes, they grow quietly—in a controlled chamber, in the roots of a maize plant, waiting to be seen.”
The Roots of the Future
Plants are far more complex than we thought. They don’t just reach for the sun—they also listen to the soil, respond to nutrients, and adjust their breathing to the rhythm of light and atmosphere.
Thanks to the pioneering work of Dr. Amiran Khabidovich Zanilov and his team, we now see a fuller picture of plant life—one where roots play a starring role in the planet’s carbon story.
So the next time you walk past a field of corn, remember: beneath your feet, a quiet carbon exchange is taking place. And science is finally starting to understand it.
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- Title: Influence of external factors on the behavior of CO2 in the root system of plants in a model experiment
- Keywords: Carbon dioxide; CO2; Gas Analyzer; Photosynthesis; Root carbon nutrition of plants
- Citation: Dudarov, Z.I., Zanilov, A.K., Altudov, Y.K. et al. Influence of external factors on the behavior of CO2 in the root system of plants in a model experiment. Carbon Res. 4, 66 (2025). https://doi.org/10.1007/s44246-025-00237-1
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About Carbon Research
The journal Carbon Research is an international multidisciplinary platform for communicating advances in fundamental and applied research on natural and engineered carbonaceous materials that are associated with ecological and environmental functions, energy generation, and global change. It is a fully Open Access (OA) journal and the Article Publishing Charges (APC) are waived until Dec 31, 2025. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon functions around the world to deliver findings from this rapidly expanding field of science. The journal is currently indexed by Scopus and Ei Compendex, and as of June 2025, the dynamic CiteScore value is 15.4.
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Journal
Carbon Research
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Influence of external factors on the behavior of CO2 in the root system of plants in a model experiment
Article Publication Date
27-Oct-2025
