New research from Bangor University and the UK Centre for Ecology and Hydrology reveals a groundbreaking approach to restoring degraded agricultural peatlands, potentially transforming these ecosystems back into vital carbon sinks. Peatlands, unique wetland ecosystems covering less than 3% of the Earth’s land surface, currently hold more carbon than all the world’s forests combined. However, centuries of drainage for agricultural use have turned many of these peatlands into significant sources of carbon emissions, exacerbating climate change. This study demonstrates how the integration of targeted rewetting strategies with biochar and iron sulphate amendments can reduce carbon loss and curb greenhouse gas emissions from degraded peat soils.
The carbon dynamics of peatlands are intricately linked to hydrology and microbial activity. Traditional drainage lowers the water table, exposing peat to oxygen, which accelerates microbial decomposition of organic matter, releasing large quantities of carbon dioxide. Rewetting peatlands by raising the water table is a recognized restoration practice that can slow down these processes. Yet, rewetting alone does not fully overturn the negative legacy effects; it faces challenges such as increased methane emissions, which are a potent greenhouse gas. This research pioneers the synergistic use of biochar and iron sulphate additions alongside water management to amplify carbon stabilization while mitigating methane release.
Conducted over a year in outdoor soil mesocosms designed to replicate agricultural peatland conditions, the experimental study meticulously tested several treatment combinations. The results strikingly show that when the water table is elevated in conjunction with biochar and iron sulphate amendments, carbon preservation is significantly enhanced compared to rewetting alone. Biochar, a stable carbon-rich material derived from pyrolyzed plant biomass, contributes persistent carbon directly to the soil matrix. More importantly, it alters microbial communities and soil biochemical processes, dampening the activity of enzymes responsible for organic matter breakdown.
Iron sulphate further intensifies carbon protection through complex mineral-organic interactions. The presence of iron fosters the formation of iron-bound carbon compounds, a phenomenon often called the “iron gate” effect, which immobilizes organic compounds by binding them to iron minerals. This mineral-carbon association effectively reduces the bioavailability of organic matter to decomposers. The combined treatment was found to suppress methane-producing archaea, which thrive under anaerobic conditions in rewetted peatlands, addressing a critical concern in peatland restoration where methane emissions can offset carbon sequestration gains.
Microbial hotspots in peat soils, areas of intense microbial metabolism, are phenotypically and functionally shifted due to the synergistic treatment. The study revealed that microbial community composition altered in ways that reduced decomposition rates without entirely hindering the necessary nutrient cycling that maintains soil health. Specifically, the suppression of soil enzymes like phenol oxidase and peroxidase that catalyze lignin and complex organic matter degradation was notable. This fine balance is vital, as overly inhibiting microbial activity can detrimentally affect peatland ecosystem functions.
The amendment synergy exerted by biochar and iron sulphate modulated redox conditions, crucial to the chemistry and biology of peat soils. Rewetting alone creates anaerobic environments conducive to methanogenesis but less favorable for oxidative enzyme activity. The presence of iron introduced microbially available iron phases that participate in redox cycling, effectively controlling electron flow and suppressing methanogenesis pathways. Simultaneously, biochar enhanced soil physical properties such as porosity and water retention, indirectly affecting microbial microhabitats and substrate accessibility.
The implications of this study extend beyond the immediate soil chemistry alterations to landscape-scale climate mitigation strategies. Peatlands represent a disproportionately large reservoir of terrestrial carbon, and restoring them as carbon sinks could significantly blunt anthropogenic carbon emissions. Integrating biochar and iron sulphate with rewetting provides a scalable and practical methodology for land managers, supplementing conventional restoration with nutrient and mineral amendments that buffer microbial carbon loss mechanisms.
Dr. Peduruhewa Jeewani, the study’s lead author, emphasized the ecological and climatological importance of the findings, stating that this synergistic approach “protects soil carbon and limits greenhouse gases” beyond what rewetting can achieve alone. This dual action—slowing decomposition and suppressing methane—addresses the complex trade-offs typically encountered in peatland restoration efforts. The controlled experimental setup allowed precise disentangling of these interactive effects, yielding insights crucial for informing future field-scale applications.
Biochar production methods, including slow pyrolysis of Miscanthus, were chosen for their ability to yield highly recalcitrant carbon forms that persist in soil. This stability ensures that carbon introduced via biochar remains sequestered for decades to centuries, contributing to long-term climate mitigation. Additionally, the influence of biochar on microbial nutrient cycling highlights its role as a soil amendment beyond carbon input—impacting nitrogen and phosphorus dynamics in peat soils prone to nutrient limitation.
Iron sulphate’s contribution is underscored by its promotion of iron redox cycling, which acts as an electron sink and mediates organic carbon stabilization in anaerobic conditions. This pathway of “mineral gating” organic carbon offers a promising avenue to reduce carbon mineralization rates in rewetted peatlands prone to rapid microbial processing. The coupling of iron chemistry with biochar’s structural and chemical properties elucidates a novel biogeochemical mechanism for enhancing peatland carbon retention.
Professor Davey Jones, co-author of the study, pointed out the broader significance for farming and climate resilience, “Healthy peatlands are critical for both farming and climate resilience.” Peatland degradation compromises both ecosystem services and agricultural productivity. Restoration techniques equipped with this emerging knowledge could promote sustainable land management practices that harmonize agricultural needs with climate objectives.
As global climate policy increasingly recognizes the importance of terrestrial carbon sinks, applying such integrative approaches to peatland restoration embodies a forward-looking strategy. This research not only advances the scientific understanding of peat soil microbial ecology and biogeochemistry but also provides actionable pathways to enhance carbon sequestration and greenhouse gas mitigation at landscape and regional scales.
This study, published in the journal Biochar, highlights a novel approach to tackling one of the most challenging climate mitigation issues—the restoration of degraded peatlands. It paves the way for future multidisciplinary research linking soil chemistry, microbial ecology, and environmental engineering to safeguard these vital ecosystems and their climate functions.
Subject of Research: Not applicable
Article Title: Restoring degraded agricultural peatlands: how rewetting, biochar, and iron sulphate synergistically modify microbial hotspots and carbon storage
News Publication Date: 10-Sep-2025
References: Jeewani, P.H., Brown, R.W., Rhymes, J.M. et al. Restoring degraded agricultural peatlands: how rewetting, biochar, and iron sulphate synergistically modify microbial hotspots and carbon storage. Biochar 7, 108 (2025). DOI: 10.1007/s42773-025-00501-y
Image Credits: Peduruhewa H. Jeewani, Robert W. Brown, Jennifer M. Rhymes, Chris D. Evans, Dave R. Chadwick & Davey L. Jones
Keywords: Soil chemistry, Environmental chemistry, Soil science
