Soil health is dependent upon maintaining appropriate levels of soil carbon, and healthy soil is vital to agricultural production. Harvest Partners César Izaurralde and Molly Jahn, in collaboration with other researchers (a full list can be found here) recently published an article in the journal Carbon Management that sought to explore current methods for quantifying changes in soil organic carbon (SOC) and the commensurate CO2 sequestration at local to national scales. In the paper (“Quantifying carbon for agricultural soil management: from the current status toward a global soil information system”), the authors describe how these current methodologies could be synthesized to create a comprehensive soil information system at a global scale.
Soils are one of the largest organic carbon depostories on the planet and so even small percentage changes in the amount of organic carbon in the soil entails massive fluctuations in total amount of carbon. Given how readily organic carbon is exchanged between soil and the atmosphere through the processes of photosynthesis and respiration, these small fluctuations also indicate large shifts in the amount of atmospheric carbon. Thus, the ability to effectively quantify and monitor changes in SOC has implications beyond just agricultural productivity- it can enable analysis of atmospheric carbon change-based climate effects.
This importance has led to the creation of numerous carbon quantification methodologies. While measuring the amount of carbon in a soil sample is relatively simple, understanding the amount of SOC in a given unit of volume and at various depths is much more complicated. Current methods are labor intensive and require highly technically-skilled individuals. Additionally, the amount of SOC introduced or removed from the soil is often a small percentage of the SOC already present. Because of this, it is more common for researchers to explore the change in carbon stocks over time, rather than the total amount of carbon at a given time period. Over a period of years, this can provide a more reliable understanding of how SOC is shrinking or growing over time. Remote sensing is one method for overcoming these hurdles. Remote sensing can gather frequent and highly-resolved data including land use, land cover, crop identification, plant biomass, and crop residues thus becoming an essential component of an integrated system to monitor SOC stocks and change. For these reasons, as well as being low-labor and cost-effective, the authors suggest that remote sensing being integrated as a component in methodologies that measure SOC.
Most current methodologies have developed at a local or national scale. This can hamper transnational research due to the lack of transparency and easy access between states. The authors suggest developing data-sharing agreements to help overcome this shortcoming and enable easier transnational access of SOC data. Further, previous SOC quantification studies have often highly aggregated the results which can limit their effectiveness at a very localized level. The authors argue this could be overcome by incorporating local land users into a crowd-sourcing program that would allow them to input local-scale management data.
The paper proposes that the integration of this crowd-sourcing program with the data-sharing agreement, combined with the use of remote sensing data as described above, could help overcome the current roadblocks in effective global quantification of SOC. Combining these suggestions (as shown in the figure below that was taken from the article) could lead to the creation of a SOC stock change quantification system that can be implemented cost effectively, at both a fine- and global-scale, and with great accessibility. The full paper can be found here.
For more details, check out the full publication which is openly available online.
Overview of the components and information flow for an approach to quantify soil carbon stock changes (and net GHG emissions) from field to national scales, purposed to support different implementation policies to remove atmospheric CO2 and sequester soil carbon. Citation.
The importance of building/maintaining soil carbon, for soil health and CO2 mitigation, is of increasing interest to a wide audience, including policymakers, NGOs and land managers. Integral to any approaches to promote carbon sequestering practices in managed soils are reliable, accurate and cost-effective means to quantify soil C stock changes and forecast soil C responses to different management, climate and edaphic conditions. While technology to accurately measure soil C concentrations and stocks has been in use for decades, many challenges to routine, cost-effective soil C quantification remain, including large spatial variability, low signal-to-noise and often high cost and standardization issues for direct measurement with destructive sampling. Models, empirical and process-based, may provide a cost-effective and practical means for soil C quantification to support C sequestration policies. Examples are described of how soil science and soil C quantification methods are being used to support domestic climate change policies to promote soil C sequestration on agricultural lands (cropland and grazing land) at national and provincial levels in Australia and Canada. Finally, a quantification system is outlined – consisting of well-integrated data-model frameworks, supported by expanded measurement and monitoring networks, remote sensing and crowd-sourcing of management activity data – that could comprise the core of a new global soil information system.