Soil Carbon: What it is and Why it is important

By: Mesa Kutz, Kim Stackhouse-Lawson Ph.D., and Logan Thompson Ph.D.  

Soil is the backbone of our society, providing the medium and nutrients we need to support our population. Soil organic carbon is an important indicator of soil quality, and helps to regulate nutrient supply, microbial activity, and soil moisture content. Soil organic carbon levels come from the interaction of ecosystem processes such as photosynthesis, respiration, and decomposition. Carbon dioxide is taken out of the atmosphere by plants via photosynthesis. This allows plants to grow and created new leaves, roots, and shoots. When plant material decays or is returned to the soil by animal deposition, it can become soil organic matter, which is plant and animal residues at various stages of decomposition. This organic matter is used by a food source for soil microbes which respire and release some of that carbon back into the atmosphere as carbon dioxide.  

One way to reduce carbon dioxide in the atmosphere is through carbon sequestration. Carbon sequestration is the process of capturing, securing and storing carbon dioxide from the atmosphere. There are two types of carbon sequestration: biological and geological. Geological carbon sequestration stores carbon dioxide in geological formations, the most promising reservoirs being porous and permeable rock bodies (Friedmann., 2007). Biological carbon sequestration stores atmospheric carbon in vegetation, soils, woody products, and aquatic environments.  Soils store one of the largest terrestrial carbon stocks on earth as soil organic matter (Oldfield et al., 2021, Yang et al., 2018). Land use change and agroecosystems have led to depleted soil organic carbon stock (McLauchlan.,Yang et al., 2018). Restoring soil carbon is essential to enhancing soil quality, sustaining and improving food production, maintaining clean water, and reducing atmospheric carbon dioxide (Lal et al., 2004). 

To increase soil carbon farmers and ranchers need to improve agricultural management practices. Utilization of proper grazing management is one practice that may help increase soil carbon content in degraded soils, and help protect soil carbon stocks in healthy rangelands (Rowntree et al., 2020; Derner et al., 2006). This includes managing grazing to leave appropriate forage residuals, allowing for adequate plant recovery prior to re-grazing, and utilizing the appropriate stocking rate. Some other best management practices are residue retention, conversion of marginal crop land to permanent pasture, utilization of livestock into crop rotations (Lam et al., 2013).   

To fight land degradation from loss of organic matter, initiatives ranging from advocacy campaigns to private sector incentive programs have been developed to restore soils (Oldfield et al., 2021). Recently, soil organic carbon protocols have been developed to bring verified carbon credits to the market and pay farmers for sequestering carbon (Oldfield et al., 2021). However, there is still issues with these markets that need improvement before widespread adoption can occur but they have the potential to be a good incentive for U.S. farmers to improve management (Dorning., 2021).  

Sources:  

Derner, J. D., T. W. Boutton, and D. D. Briske. 2006. Grazing and ecosystem carbon storage in the North American Great Plains. Plant and Soil. 280:77-90. Doi:10.1007/s11104-005-2554-3 

Dorning, M. 2021. Biden’s USDA Chief Is Exploring Making a Carbon Bank for Farmers. Bloomberg.com. Retrieved September 10, 2021. Accessed from: https://www.bloomberg.com/news/articles/2021-03-05/biden-s-usda-chief-is-exploring-making-a-carbon-bank-for-farmers 

Friedmann S.J. 2007. Geological Carbon Dioxide Sequestration. Elements3:179-184.            Doi: 10.2113/gselements.3.3.179  

Lal, R., Griffin, M., Apt, J., Lve, L., and Morgan, M.G. 2004. Managing Soil Carbon. Science:304, 393. Doi: 10.1126/science.1093079  

Lam, S.K., Chen, D., Mosier, A.R., and Roush, R. 2013. The potential for carbon sequestration in Australian agriculture soils is technically and economically limited. Scientific Reports, 3:2179. Doi: 10.1038/srep02179 

Oldfield, E.E., Eagle A.J., Rubin, R.L., Rudek, J., Sanderman, J., Gordon, D.R., 2021. Agriculture soil carbon credits: Making sense of protocols for carbon sequestration and net greenhouse gas removals. Environmental Defense Fund, New York, New York. Accessed from: edf.org/sites/default/files/content/agriculture-soil-carbon-credits-protocol-synthesis.pdr.  

Rowntree, J. E., P. L. Stanley, I. C. F. Maciel, M. Thorbecke, S. T. Rosenzweig, D. W. Hancok, A. Guzman, and M. R. Raven. 2020. Ecosystem impacts and productive capacity of a multi-species pastured livestock system. Front. Sustain. Food Sys. 4:544984. Doi: 10.3389/fsufs.2020.544984 

Yang, Y., Tilman, D., Furey, G., and Lehman, C. 2019. Soil Carbon sequestration accelerated by     restoration of grassland biodiversity. Nature Communications, 10:718. Doi: 10.1038/s41467-019-08636-w