What’s the difference between soil carbon, soil organic carbon, and atmospheric carbon? If you want to understand carbon sequestration’s relationship to soil fertility, it’s important to define these terms accurately. There’s more to consider than you might think, including carbon’s relationship to climate. The table below explains.
Property | Soil Carbon | Soil Organic Carbon | Atmospheric Carbon |
Location | In all soil forms (organic + inorganic) | Within soil organic matter | In the atmosphere (mainly CO2 and CH4) |
Composition | Organic + inorganic carbon | Organic matter only | Gaseous forms (CO2, CH4) |
Role in Ecosystem | Total soil carbon pool | Soil health and fertility | Climate regulation |
Interaction with Climate | Potential for carbon storage | Sequesters atmospheric CO2 | Contributes to warming |
Keep reading to learn more.
Soil Carbon
Soil carbon (SC) includes all forms of carbon in soil – both organic and inorganic.
Organic carbon is transferred into the soil by plant roots, or through the decay of plant material or soil organisms when they do. Yet organic carbon isn’t just found in soil. It’s also stored above ground in the visible parts of grass, shrubs, and trees.
Inorganic carbon is typically found in carbonates such as calcium carbonate, a common substance in rocks. Typically, inorganic carbon is found in arid and semi-arid regions; however, limestone deposits in temperate climates like Adams, Massachusetts also contain calcium carbonate.
Soil Organic Carbon
Soil organic carbon (SOC) comes from plant roots or the decay of plant materials or soil organisms. It’s found only in the soil, and not above ground in trees or in the atmosphere. SOC is essential for soil fertility, but it’s also a carbon sink that may help address climate change.
Unlike soil carbon, soil organic carbon does not contain inorganic substances like carbonates. That may seem obvious, but it’s a key difference between soil organic carbon and soil carbon: terms that are easy to use interchangeably, but that are not one and the same.
Atmospheric Carbon
Atmospheric carbon exists in the atmosphere mainly as carbon dioxide (CO2) and methane (CH4), both of which are greenhouse gases. The U.S. EPA says that methane is 28 more times as potent at trapping heat in the atmosphere but it has a considerably shorter life than carbon dioxide. In other words, methane breaks down much faster in the environment than carbon dioxide.
The sources of atmospheric carbon are many and range from tailpipe emissions to industrial processes to agriculture. As the video below explains, Go Natural Education believes that agriculture has been unfairly demonized and that carbon – as this article explains – needs to be understood more clearly because of its role not just to climate change, but to soil fertility.