How Does Carbon Cycle Through Agricultural Systems?

Content has been adapted from The Context Network  “Get Smart, Stay Smart” Ag Carbon Service.

The short answer: Carbon cycles through agricultural systems through plant photosynthesis, biomass decomposition, and animal production. Each point in the cycle represents an opportunity to change management practices to increase sequestration of atmospheric carbon in the soil.

Graphic depicting the pathways of carbon exchange between livestock, crop residue, soil, crops, and atmosphere.

Figure provided by U.S. Farmers and Ranchers in Action and the Context Network, LLC.

The big picture: Here, the U.S. Farmers and Ranchers in Action (in work performed by The Context Network), represent the carbon cycling through a corn-soybean rotation with livestock contributing manure fertilizer to the system.

  • Plant photosynthesis removes carbon from the atmosphere, converting carbon dioxide and water to glucose, a sugar molecule, which provides energy and contributes to plant biomass as it grows.
  • When a crop is harvested, some or all of its biomass remains in the soil. Microbes decompose roots below the ground, while residue left at the soil surface provides soil cover and food for livestock.
  • Manure generated by livestock feeding on crops and crop residue is rich in nutrients and microbes. Spreading livestock manure on agricultural soil “closes the loop,” returning plant-derived nutrients and carbon to the soil itself.
  • During decomposition, soil microbes convert the longer carbon chains in biomass into simpler elements, taking in oxygen and releasing carbon dioxide in the process.

At each point in the cycle, managing the agricultural system with carbon in mind can help producers reap the benefits of improving soil organic carbon.

Photo courtesy of USDA.