The connection between organic carbon and soil health

Our new season of Carbon College has launched, including an entire course on carbon systems. Check out the video above as well as this article to learn about the importance of organic carbon for soil health and crop yields. For more on carbon farming, explore the entire series of Carbon College’s free video courses.

Carbon is one of the most common elements on the planet and the most common element in living organisms. It’s also key to soil function and productivity. Soil health and yield generally improve when organic carbon levels in the soil increase. When soils have high levels of organic carbon, they contain more pore space. This allows for movement of gasses and water, which improve crop growth and health. Soils with high levels of organic carbon also have higher water holding capacity, improved drainage of excess water, and reduced erosion and nutrient loss potential, among other benefits.

Different agricultural practices can increase or decrease carbon stocks in the soil. This will then impact susceptibility to drought or excess precipitation, while also impacting field accessibility and long-term field productivity. What can you do to increase soil carbon stocks?

There are three main strategies: 

Cover crops are a great way to do this. Cover crops extend the amount of time photosynthesis converts carbon dioxide into oxygen, plant biomass, and soil carbon. Additionally, soil amendments like manure and sewage sludge, added on top of fields as fertilizer, can directly increase soil carbon stocks through the increase of biomass available for conversion into soil organic matter and soil carbon.

Plants that have deeper root systems or that allocate more carbon to their roots will increase carbon retention in the soil. As soil depth increases, there’s less oxygen and therefore less oxidation–the process that sends CO2 back to the atmosphere. Prairie grasses are an example of a plant with deep root systems. Soils that formed over thousands of years in tall grass prairies built up a lot of organic matter due to excellent biomass production and protection from oxidation in poorly-drained soils. These deep root systems move carbon into soil depths with lower oxidation rates and gradually increase carbon stocks.

Planting cover crops with deep root systems can help build soil carbon levels. Indigo’s Cover Crop selector can help you choose the best cover crop(s) for your fields based on the challenges you’re trying to solve.

Tillage exposes soil carbon to oxygen. This increases soil carbon decomposition as well as the release of carbon back into the atmosphere. This is why reducing tillage and switching to no till–practices that keep the physical stability of the soil intact will protect the amount of organic carbon in the soil and decrease the amount released into the atmosphere. Soil erosion can also expose soil to oxidation while also contributing to the direct loss of soil organic matter through soil loss.

Cover crops can also reduce soil erosion and the resulting loss of carbon through erosion. Additionally, overusing N fertilizer or inefficiently timing its application will cause increased decomposition of organic matter and soil carbon loss.

When you implement practices that increase carbon additions to the soil, retain that carbon, and protect it from breakdown or loss you’ll see your soil carbon levels increase. Over time, you’ll reap the numerous agronomic and economic benefits associated with high soil carbon levels.

It’s also important to maintain nitrogen levels in soils. Try out our Nitrogen Generation Estimator to discover just how much different cover crops can contribute to your nitrogen needs.