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The Dirt | Healthy Soil Helps the Planet! Part 5

Welcome to the Willamette Valley Regenerative Landscape Coalition Soil Carbon Blog series!

The opinions, beliefs and viewpoints expressed by the author of this five-part blog series do not necessarily reflect the opinions, beliefs and viewpoints of Benton Soil & Water Conservation District representatives.

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Densely planted landscape, at the home of Marion Thenell, 35th and Fillmore, Corvallis, OR. photo C. Phillips 2019

Part 5: Limits to soil carbon sequestration

There is understandable hype about the potential of carbon sequestration to affect climate change. Some of the numbers are promising:

Every 1% of stored soil organic matter/acre keeps around 10 tons of carbon out of the atmosphere.

This equates to around 35 tons of CO2. This applies to normal heavy, clay soils common in much of the U.S. In lighter sandy soils, the numbers would be lower, but still significant. Scientists suggest we need to remove 100 to 200 billion tons of carbon from the atmosphere. This number seems staggering, but the earth has billions of acres of depleted soil that can be managed to take in more carbon.

There is a certain amount of concern over how realistic soil carbon sequestration really is. We have to be careful about promising too much and being unrealistic. It is absolutely true that we are only at the starting point of understanding the possibilities.

One common criticism of soil carbon sequestration is that some carbon dating studies have shown only very slow soil carbon increases. This may be true in the soils that were tested, but if we look at the real-life examples from Part 4 of this blog series, we see evidence of fast soil carbon gains.

The real-life examples mentioned in Part 4 of this blog series are what give us hope that soil carbon sequestration can be a big part of the climate change solution.

Universities and research groups use modeling to predict carbon sequestration. Some of these models have suggested that soil organic matter levels can be increased only modestly. There is one common problem with these models. They generally don’t take into account soil carbon increases due to root exudates. They often only look at OM increases due to biomass or plant growth (much of which tends to decompose anyway).  Models tend to rely on old, established science, while waiting for newer ideas to be fully vetted.

Our ability to investigate soil is growing by leaps and bounds. We can expect to understand more and more about soil carbon sequestration in the coming years. In the meantime, we can follow the lead of real-life examples that seem to work.

It is important to be realistic about soil carbon sequestration, but there is enough evidence that it can be a very effective tool with dealing with climate change. We simply need to start taking action now. We can, and should, be emulating existing, and experimenting with new soil-building methods until new understanding leads us to even better methods.