Drained agricultural peatlands are a major source of greenhouse gas emissions due to the decomposition of stored carbon. Restoring these vital ecosystems is a global priority, and one promising strategy involves rewetting the soil and adding amendments. A new study by Peduruhewa H. Jeewani et al. in the journal BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More investigates how combining rewetting with biochar and iron sulfate can effectively preserve carbon by altering the soil’s microbial communities and enzyme activity

Peatlands are the largest terrestrial carbon reservoir on Earth. However, a significant portion of the world’s peatlands have been drained and converted for agriculture, leading to their degradation. This drainage exposes the peat to oxygen, accelerating the decomposition of organic matter by soil microbes and releasing massive amounts of carbon dioxide (CO2​) and other greenhouse gases into the atmosphere. Rewetting is a primary restoration method, but it can sometimes have an unwanted side effect: an increase in methane (CH4​) emissions. To address this, scientists are exploring the use of soil amendments that can work with rewetting to promote carbon storage.

This study tested a combination of a high water table (rewetting), biochar, and iron sulfate (FeSO4​) to see how they would affect peat’s ability to store carbon. Biochar, a carbon-rich material produced from biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, is known for its stable, persistent nature. The researchers also added FeSO4​ to the mix, hypothesizing it would suppress methanogenesis, a process that produces methane.

The experiment, conducted over one year, revealed that a high water table combined with biochar and FeSO4​ was the most effective treatment for preserving peat carbon and suppressing microbial activity. Specifically, this combination led to a decline in the abundance of key decomposers, with Actinobacteria reduced by approximately 22% and Ascomycota by 61%. This suppression of decomposers and their enzyme activity helps to lock carbon in the soil rather than releasing it into the atmosphere.

The study identified both abiotic and biotic mechanisms behind these successful results. On the biotic side, the high water table and amendments significantly altered the microbial community structure. The high water table created anaerobic conditions, which suppressed the growth of decomposers like Actinobacteria and Ascomycota that thrive in aerobic (oxygen-rich) environments. In treatments with a low water table, these decomposers dominated, leading to higher rates of carbon mineralization.

Biochar also played a key role by modifying the microbial community and simplifying the fungal co-occurrence networks, indicating that it altered the available ecological niches for K-strategist fungi. The biochar addition suppressed methane emissions by 20.7 t CO2​e ha−1yr−1. On the abiotic side, the FeSO4​ addition supported the “iron gate” mechanism, where iron binds with organic carbon to make it more stable and less susceptible to decomposition. This was particularly evident in the low water table treatments, where iron-bound organic carbon content was higher.

The findings of this research provide strong evidence that implementing biochar and FeSO4​ amendments alongside water table management is a practical and scalable approach for restoring the carbon storage capacity of agricultural peatlands. This integrated strategy offers a way to enhance carbon preservation while simultaneously reducing greenhouse gas emissions. The most effective treatment—the combination of a high water table with biochar and FeSO4​—demonstrated an effective peat carbon preservation of 190 t ha−1 yr−1. This is significantly higher than the 166 t ha−1 yr−1 for the control high water table treatment and 164 t ha−1 yr−1 for the low water table treatment. This approach offers a promising path forward for sustainable agriculture, climate change mitigation, and the restoration of degraded peatlands.

Source: Jeewani, P. H., Brown, R. W., Rhymes, J. M., Evans, C. D., Chadwick, D. R., & Jones, D. L. (2025). Restoring degraded agricultural peatlands: how rewetting, biochar, and iron sulphate synergistically modify microbial hotspots and carbon storage. Biochar, 7(108).