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Soils from organic farms are key to climate change mitigation

Food systems contribute 19%– 29% of human-caused global greenhouse gas emissions, with agricultural production contributing around 90% of total food system emissions. Recent research has also shown that conventional farming systems degrade the carbon stores in our soils. Poor agricultural practices lead to a breakdown of soil organic carbon that then is released into the atmosphere as the greenhouse gas carbon dioxide.

A new study found that agriculture is linked directly to a loss of 133 billion metric tons of carbon globally, with the rate of loss rapidly accelerating over the past 200 years. However, a growing body of research demonstrates that organic agriculture can build soil organic carbon and increase carbon sequestration compared to conventional farming, thus contributing to climate change mitigation.

Researchers at Northeastern University, in collaboration with The Organic Center, conducted the study to examine the potential for organic agriculture to mitigate climate. Comparing over 1,000 soil samples from across the country, this study found that soils from organic farms store more carbon and do so for longer periods than soils from non-organic farms. These results show that organic farming has an important role to play in sustaining healthy soils and combatting climate change. 

Healthy soils are essential for robust and resilient crop production, and the amount of soil organic matter is one of the most critical components of a healthy soil. Organic matter is all the living and dead plant and animal material in our dirt that make it more than dirt—earthworms and insects and microorganisms, plant and animal residues, fermented compost, decomposed leaves and plant roots. Soils high in organic matter support healthy crops, are less susceptible to drought, and foster a diversity of organisms vital to soil health. Soils rich in organic matter can also maintain carbon for long periods, offsetting greenhouse gas emissions by storing the carbon from carbon dioxide in the atmosphere deep in the soil.

Two pools of carbon molecules make up soil organic carbon. One pool constantly is broken down by microbes, and fluctuates widely from season to season.  While this short-lived carbon pool is important for soil health, it has little role in long-term carbon sequestration that is key to fighting climate change. Humic substances, on the other hand, are the gold standard of organic matter.

These molecules resist degradation and can remain in the soil for hundreds and sometimes thousands of years. They do not just mean healthy soil; they are also one of the most effective ways to mitigate climate change. The more humic substances in a soil, the longer that healthy soil is trapping and keeping carbon out of the atmosphere. Quantifying this pool of carbon is key to providing an accurate understanding of long-term soil health and carbon sequestration.

Since 2008, the National Soil Project at Northeastern has been measuring the different components of soil organic matter from conventional farms across the United States. In 2014, The Organic Center teamed up with the National Soil Project to compare the project’s conventional soil samples to organic soil samples. The Organic Center worked with the researchers as organic experts through the project, and enlisted hundreds of farmer “citizen scientists” to send in soil samples from their farms. 

The study shows that the components of humic substances—fulvic and humic acids—were consistently higher in organic than in conventional soils. The research found that, on average, soils from organic farms had:

 • 13 percent higher soil organic matter

 • 150 percent more fulvic acid

 • 44 percent more humic acid

 • 26 percent greater potential for long-term carbon storage.

This is the first time scientific research has given an accurate picture of the long-term soil carbon storage on organic versus conventional farms throughout the U.S. // 

Tracy Misiewicz is the Associate Director of Science Programs for The Organic Center (tmisiewicz@organic-center.org).

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