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Soil Carbon Storage
Context:
Researchers at Kansas State University (K-State) are investigating how various farming practices influence the amount of carbon stored in soil.
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- Researchers utilised the Canadian Light Source (CLS) at the University of Saskatchewan (USask) and the Advanced Light Source in Berkeley, California, to analyse soil from a Kansas cornfield that had been farmed without tilling for 22 years.
- Over this period, the farm implemented various soil nitrogen management practices, including no fertiliser, chemical fertilisers, and manure/compost fertilisers.
- Researchers discovered that soil enriched with manure or compost fertiliser retains more carbon compared to soil treated with chemical fertilisers or left untreated.
Soil carbon storage
Also known as soil carbon sequestration, it refers to the process of capturing and storing atmospheric carbon dioxide (CO2) in soil as organic carbon. This process is crucial for mitigating climate change, as soils hold three times more carbon than the atmosphere.
Mechanisms of Soil Carbon Sequestration
- Photosynthesis and Organic Matter: Plants absorb CO2 during photosynthesis, converting it into organic compounds.
- When plants die, their residues and root exudates contribute to soil organic carbon (SOC) as they decompose, aided by soil microorganisms.
- Microbial Processes: Microorganisms play a significant role in the formation and preservation of SOC.
- Research indicates that microbial carbon use efficiency (CUE) is a key factor influencing SOC storage.
- Higher CUE correlates with increased SOC content, suggesting that microbial activity is critical for maintaining carbon in soils.
- Agricultural Practices: Implementing specific farming practices can enhance soil carbon storage. These include:
- Conservation Tillage: Reducing soil disturbance through low-till or no-till farming minimises the release of stored carbon.
- Cover Cropping: Planting cover crops like clover or beans after the main harvest helps maintain carbon levels in the soil year-round.
- Crop Rotation and Diversification: Varying crops can improve SOC levels by increasing the diversity of plant residues returned to the soil.
- Organic Amendments: Adding compost or manure boosts organic matter content, which enhances soil structure and carbon retention.
Limitations of Soil-Based Carbon Storage:
- Widespread Adoption Challenges: For soil-based carbon sequestration to be effective, many farmers would need to change their farming practices, both now and for the long term which presents significant social and economic challenges.
- Impact of Climate Change: Global warming may accelerate the decay of soil organic matter, leading to increased carbon losses.
- In the Arctic, thawing permafrost is already releasing CO2, which could create a self-reinforcing feedback loop: as soil carbon is lost, it contributes to further warming and additional carbon release.
- Effectiveness and Necessity: Soil-based carbon sequestration cannot remove carbon from the atmosphere as quickly as we are currently adding it.
