Boulder County reports limited impact in first year

Carbon sequestration, the process of organic material absorbing carbon dioxide from the atmosphere, have become buzzwords in recent years as communities search for ways to reduce carbon emissions and combat climate change.

However, while the scientific theory is sound — healthier soils sequester more carbon — farmers and ranchers are still trying to figure out how to effectively apply carbon farming practices, especially from a financial standpoint. As the agricultural community experiments with different applications, those on the ground urge the public not to lean on soil carbon sequestration as a potential windfall in the fight against climate change.

“People are going to have to be patient, it’s going to take a long time to figure this out,” said Elizabeth Black, head of the Citizen Science Soil Health Project that analyzes soil samples from all over Boulder, Larimer and Weld counties. “Climate change is really scaring people and they want a solution. When they hear about soil carbon sequestration there is this tendency for people to say this is great, farmers are going to fix this. That is not fair or realistic. Everybody has to do their part. People in cities need to figure out what they’re going to do to fix it on their end, too.”

Ideally any investment farmers and ranchers make to improve the health of their soil, such as applying compost, planting cover crops or updating irrigation systems, would be recouped by way of more productive fields and larger yields. A healthier soil also would allow for more efficient use of water and a higher rate of carbon absorption.

According to the Berkeley Food Institute, forests, croplands, urban trees and organic material in landfills offset 11.5% of U.S. carbon emissions. However, U.S. cropland currently only sequesters 8.4 million metric tons of carbon dioxide each

year. If soil health was improved, the Berkeley Food Institute estimated the potential for cropland to annually sequester an additional 2% of U.S. carbon emissions.

Last spring, Boulder County Parks and Open Space and Colorado State University teamed up to design a carbon farming experiment on the 120-acre Campbell & Quicksilver Farm outside of Longmont.

At the behest of CSU agricultural scientists, Paul Schlagel, owner of the Campbell and Quicksilver farm properties, set aside 10 acres for the experiment and split it into four sections.

On the first plot, which was used as a control, Schlagel left the field fallow during the off-season and did not use any kind of compost or fertilizer.

On the second and third plots, Schlagel planted a cover crop of rye and hairy vetch, the roots from which were supposed to keep nutrients in the soil and reduce erosion throughout the winter. It did not produce any valuable byproduct though.

When it was time to plant the cash crop, which was corn in this instance, the cover crop was killed using an herbicide and lightly tilled back into the soil to limit disturbances to the microbes and minimize the release of carbon already stored within, while also returning the nutrients used to grow the cover crop.

After the corn was planted, Schlagel applied compost to the third and fourth plots, ultimately creating four distinct variations on the experiment — one that only used a cover crop, one that only used compost, one that used neither and one that used both.

While the levels of carbon in the soil rose slightly for those that used compost and cover crop, Blake Cooper, the agricultural resources division manager for Boulder County Parks and Open Space, said there was no statistically significant difference between the soils on any of the plots.

“It’s trending in the right direction, the carbon is highest in some of the compost treatments, but the study just doesn’t provide that ‘aha’ moment,” he said. “That was expected in the first year, though, that’s why it’s a five-year study. We’ll just have to wait and see (if these practices produce better results in the future).”

Mark Easter, a senior research associate at CSU, said that though there was no statistically significant impact measured this year, he estimated the 10 acres used for the pilot program will sequester 35 tons of CO2 each year as a result of carbon farming practices, roughly equivalent to the emissions released by 7½ cars.

Had the practices not been applied, he added, the soil would not have sequestered any carbon as it has reached a “dynamic equilibrium” that does not allow for additional storage.

Similarly, crop yields were slightly higher on the plots that used compost, though there was no statistically significant difference. The plots that used cover crops also were negatively affected by the hairy vetch not being completely eliminated by the herbicide, allowing it to compete with the corn for nutrients and water.

While Cooper is confident these experiments will bear more fruit as practices improve in the years to come, he said the real hurdle will be reducing the costs of carbon farming, and compost in particular.

“Economics-wise this does not pencil out very well with $40 per ton compost,” he said.

“Take that down closer to $10 per ton and you start getting into the range where the farmers would be able to at least partially replace some costly synthetic fertilizers with a compost product that is better for the environment and sequesters more carbon in the soil, but still maintains or improves soil fertility and crop productivity. Getting compost available en masse and at a reasonable price point will be the ticket to making this happen or not.”