{"id":3228,"date":"2024-02-16T15:42:42","date_gmt":"2024-02-16T15:42:42","guid":{"rendered":"https:\/\/www.agricarbon.co.uk\/education-hub\/measuring-soil-carbon-beyond-30cm\/"},"modified":"2025-09-18T13:46:48","modified_gmt":"2025-09-18T12:46:48","slug":"measuring-soil-carbon-beyond-30cm","status":"publish","type":"education-hub","link":"https:\/\/www.agricarbon.co.uk\/en-us\/education-hub\/measuring-soil-carbon-beyond-30cm\/","title":{"rendered":"Measuring Soil Carbon Beyond 30cm"},"content":{"rendered":"\n

Going Beyond 30cm<\/h3>\n\n

Measuring soil carbon stocks requires precision. With high-integrity data, you can ensure that your carbon management strategies are well-informed and compliant with MRV protocols. Agricarbon’s methodology is based on the direct measurement of Soil Organic Carbon (SOC) and is driven by our guarantee to always deliver robust and precise data for our clients. While SOC measurements have typically focused on the top 30cm, we extract samples beyond this range, representing the growing evidence that deeper soils play a vital role in carbon storage.<\/p>\n\n

In this article, we delve into the rationale behind our approach, the growing evidence, and the need for high-integrity data, all of which highlight the importance of looking deeper.<\/p>\n\n

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A quote from Agricarbon’s Tom Sadan on the benefit of measuring beyond 30cm.<\/em><\/figcaption><\/figure>\n\n

What is Soil Organic Carbon?<\/strong> <\/h3>\n\n

Soil Organic Carbon (SOC) is a key indicator of soil health and a critical factor in the global carbon cycle. It has multi-faceted impacts on soil, such as fertility, agricultural productivity, biodiversity, and atmospheric carbon dioxide (CO2<\/sub>) fixation. Understanding SOC dynamics is essential for developing strategies to achieve Net Zero emissions, advancing Regenerative Agriculture, and enhancing soils’ role in mitigating climate change. <\/p>\n\n

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Field Operator, Nathan Jones, presents the 1m long tube that captures a soil core used when measuring soil carbon. <\/em>Photo taken by TerraVesta<\/a><\/em><\/figcaption><\/figure>\n\n

Why is Understanding the Soil Carbon Cycle Important?<\/strong><\/h3>\n\n

Soil carbon sequestration is a complex process that encapsulates the capture and storage of atmospheric carbon dioxide in the soil. The soil carbon cycle involves carbon entering the soil through plant compounds and residues, undergoing transformation by microorganisms into stable forms, and moving deeper via stabilization. This results in long-term carbon storage. <\/p>\n

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Understanding the soil carbon cycle, including the distinction between labile and stable carbon, is crucial. Labile carbon, while more reactive and less stable, plays a key role in nutrient cycling and soil fertility. Stable carbon, typically found at deeper levels, contributes to long-term carbon sequestration. The study, \u2018Soil Organic Matter Storage in Temperate Lowland Arable, Grassland and Woodland Topsoil and Subsoil\u2019<\/a> by Antony et al. (2022) evidences the importance of measuring soil carbon below 30cm. Their research revealed that up to 50% of soil organic carbon could be stored below this depth. <\/p>\n\n

Measuring Soil Carbon: The Need for Deeper Analysis<\/strong><\/h3>\n\n

Recognizing that significant amounts of carbon are stored below 30, highlights the need for intentional and robust soil carbon auditing. By focusing solely on the top 30cm, we risk underestimating the soil’s carbon storage capacity and, consequently, the potential for soil to mitigate climate change. We have found that when measuring soil carbon, focusing on the 30-60cm range is both practical and essential. Our clients can take advantage of our unique offer, balancing feasibility with the need for comprehensive data. Sampling deeper than 30cm allows them to substantiate claims for detecting soil carbon stock changes and provides a more complete picture of soil carbon dynamics. <\/p>\n\n

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Bulk Density is captured with every extracted soil core.<\/em><\/figcaption><\/figure>\n<\/div>\n

Measuring Changes in Bulk Density<\/strong><\/h3>\n\n

Understanding soil carbon stocks isn’t just about measuring organic carbon content; it’s also about quantifying bulk density. Bulk density is defined as the mass of dry soil per unit volume, including the air space. <\/p>\n\n

When bulk density is measured at greater soil depths, its quantity typically increases. This is because deeper soil layers are often more compacted due to the weight of the soil above. This compaction results in less pore space for air and water, leading to higher bulk density. However, variations can occur due to factors like soil type and land use. Changes in bulk density often occur with shifts in management practices and can change the mass of soil sampling for a specific depth increment (e.g., 0\u201330 cm). Because this change can result in either under- or over-account SOC stocks, the equivalent soil mass (ESM) calculation is introduced. This is a method that can help with assessing SOC to account for differences in soil masses caused by soil management. <\/p>\n\n

A major problem with measuring soil carbon at a fixed depth of 30cm is that it does not account for changes in soil bulk density that often occur with shifts in management practices. Plus, to be able to account for non-linear rates of change for SOC and bulk density across the soil profile, using multiple depth intervals (e.g., 0\u201330, 30\u201360 cm as opposed to 0\u201330 or 0\u201360 cm) for carbon stock calculation is essential. For more info on how using a fixed depth underestimates SOC sequestration, the 2022 study by Rovira, Sauras-Yera, and Romany\u00e0 is a great place to start:, \u2018Equivalent-mass versus fixed-depth as criteria for quantifying soil carbon sequestration: How relevant is the difference?<\/a>\u2019<\/p>\n

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The extracted soil core is sent to Dundee for analysis. <\/em><\/figcaption><\/figure>\n<\/div>\n

Protocols and Measurement Standards<\/strong><\/h3>\n\n

When measuring soil carbon, protocols like the FAO-GSCOC, GHG Protocol LS&R, and VM0042, while stipulating a minimum of 30cm, encourage deeper sampling. Agricarbon\u2019s methods already comply with the standard requirements by sampling up to 1m deep, but by surpassing the typical 30cm depth, we also ensure a more comprehensive soil carbon quantification and analysis. <\/strong><\/p>\n\n

As the latest advancements in soil science suggest; sampling to 60 cm (using multiple depth increments) should be considered the practice when quantifying change in SOC stocks. A great example is the 2024 study by Raffeld et al., \u2018The importance of accounting method and sampling depth to estimate changes in soil carbon stocks\u2019<\/a>. Our approach not only adheres to but also advances existing standards, providing detailed data for robust soil carbon management and reporting, in line with IPCC recommendations. <\/p>\n\n

Agricarbon’s Enhanced Approach to Measuring Soil Carbon<\/strong><\/h3>\n
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By sampling up to 1m, we ensure a holistic assessment of SOC, which is vital for:<\/p>\n\n