In a recent article published in Proceedings of the National Academy of Sciences, researchers addressed the urgent need for sustainable agricultural practices capable of enhancing food security while mitigating climate change impacts. Recognizing the dual challenge of increasing crop productivity and reducing greenhouse gas (GHG) emissions, the study centers on biochar—a carbon-rich product derived from biomass pyrolysis—as a potential solution.
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The authors emphasize the importance of understanding the long-term effects of biochar application, as most existing research focuses on short-term outcomes. By systematically analyzing a comprehensive collection of peer-reviewed studies, the paper aims to elucidate the enduring benefits of biochar in improving soil quality, crop yields, and its role in climate change mitigation.
Background
Biochar has gained prominence due to its unique ability to improve soil fertility through increased organic carbon stocks and its potential to reduce GHG emissions, especially methane (CH4) and nitrous oxide (N2O). Its production process involves pyrolyzing biomass residues, which sequesters carbon and facilitates the development of soil amendments that can influence microbial communities and soil chemical properties.
Despite its promising attributes, the effectiveness of biochar varies across different environmental conditions, application regimes, and crop systems. Prior studies have highlighted inconsistent results, largely limited to short-term experiments.
The study underscores the need for a comprehensive, long-term perspective to inform best practices and policy recommendations, considering factors such as soil properties, climate variability, and application frequency.
The Current Study
The researchers conducted an extensive literature review, gathering data from multiple scientific databases, including Web of Science, Scopus, Google Scholar, CNKI, and Wanfang. They focused on studies published up to February 2025 and included experimental data that reported the effects of biochar on crop yields, GHG emissions, and soil organic carbon (SOC) content over at least one full crop-growing season.
The criteria mandated that studies provide data for control (without biochar) and treatment plots, specify application frequency (single or repeated applications), and report experimental durations.
To quantify biochar’s effects, the team employed meta-analytic techniques, calculating response ratios and weighting effect sizes by inverse variance. They used multilevel models to account for variability within and across studies, considering study identifiers as random effects.
The analysis also incorporated long-term field experiments that tracked GHG emissions over multiple years, enabling assessment of biochar’s cumulative impacts on global warming potential (GWP) and greenhouse gas intensity (GHGI).
Results and Discussion
The findings demonstrate that long-term biochar application consistently enhances crop productivity, with annual applications yielding more sustained benefits than single, one-time treatments.
Crop yields increased by approximately 11% under repeated application regimes, with benefits accumulating over time.
Single applications, however, showed diminishing effects after three to five years, likely due to biochar aging processes such as pore collapse and reduction in surface area.
The study highlights that environmental factors such as soil pH, temperature, and precipitation significantly influence biochar’s efficacy. Specifically, alkaline soils exhibited more substantial reductions in N2O emissions, while high temperatures and heavy rainfall tended to diminish biochar’s benefits due to accelerated microbial decomposition.
Soil organic carbon content increased markedly, with annual applications boosting SOC by over 50%, and these effects became more pronounced with prolonged use.
GHG mitigation was notably effective in paddy fields, where methane emissions were reduced by over 13%, especially in acidic soils. These reductions were linked to improved soil aeration and microbial community shifts that favor methane oxidation.
The discussion emphasizes that periodic reapplication strategies are essential to offset biochar aging and sustain its positive effects. The authors also recognize potential drawbacks, such as soil pH elevation beyond optimal levels with excessive, repeated applications, possibly inhibiting plant growth and soil microbial diversity.
They advocate for tailored application schedules aligned with local conditions to maximize benefits while minimizing risks.
Conclusion
The study concludes that biochar presents a viable and scalable option to simultaneously enhance food security and combat climate change.
Repeated, long-term applications are more effective than single, one-time treatments, emphasizing the necessity for implementation frameworks that optimize application frequency and rates based on specific environmental contexts.
The findings support the development of targeted guidelines for biochar use, considering soil type, climate, and crop systems.
The authors highlight the importance of policy support, including subsidy schemes, to facilitate broader adoption among farmers wary of initial costs. They call for continued research, particularly large-scale demonstration trials, to refine application strategies and confirm long-term benefits.
Overall, biochar offers a promising pathway toward sustainable agriculture, provided that long-term effects, environmental considerations, and economic factors are carefully managed.
Source:
Yang J., et al. (2025). Sustained Benefits of Long-Term Biochar Application for Food Security and Climate Change Mitigation. Proceedings of the National Academy of Sciences, 122(33), e2509237122. DOI: 10.1073/pnas.2509237122, https://www.pnas.org/doi/10.1073/pnas.2509237122