19 Story Idea? Email Paul.Nolan@Farms.com Better Farming | April 2024 Carbon Sequestration Farmers are sometimes criticized in environmental sustainability conversations, but soil carbon sequestration is one opportunity to turn that around. Carbon sequestration is the removal of carbon, in the form of carbon dioxide, from the atmosphere, where it will then be stored in another form, often in soil or plants. Some Prairie producers are now seeing that in addition to improving public perception of the industry, managing farmland to increase soil carbon also benefits crop and pasture productivity, drought resilience, and erosion. How does soil store carbon and how can farmers reap the benefits? What is carbon sequestration? There are a few ways that carbon is stored. It can be stored in soil or plant material and can be organic or inorganic and living or dead material. Dr. Cameron Carlyle, associate professor in the department of Agricultural, Food & Nutritional Science at the University of Alberta, has been mapping soil carbon in grasslands across the Prairies. “When we are thinking about carbon sequestration, we are usually talking about moving carbon from the atmosphere into soil, where it gets used by plants and converted into other compounds, which the plant then releases and it gets bound into the soil,” explains Carlyle. “The main benefit is that those carbon molecules are no longer greenhouse gases contributing to climate change. The other benefits for soil are that with that sequestration, carbon increases in the soil and that means organic matter in soil increases. That’s beneficial for the nutrients in the soil, which can hold more water and has benefits for plant growth and forage production.” Cedric MacLeod, executive director of the Canadian Forage & Grassland Association, says that the process of carbon storage involves the interaction of a number of factors. “It’s a complex interaction between plants, soil, and the sun,” explains MacLeod. “Photosynthesis generates sugars, and plants use carbon and put it into their roots. When a plant dies, the roots stay behind, and that becomes organic matter through an interaction with many microscopic living creatures within the soil structure.” MacLeod also notes that there is an equivalent amount of plant below the ground as what can be seen aboveground. Macleod says, “that same amount of plant material is still left behind under the soil surface and that carbon drives microbial function. They chew on the roots and mineralize the material and turn it into organic matter, which will go into the next crop, and whatever is left behind contributes to carbon sequestration long-term.” These root systems also allow for greater water-holding capacity during drought without waterlogging in wet years, improving crop resilience. Macleod explains that lignin, a fibrous component of the plant, is more challenging for microbes to break down and remains in the soil longer-term as a recalcitrant source of carbon. Instead, the microbes target the “juicy” part of the plant, which can then be mineralized and made available, or is more susceptible to re-release. “It’s a very dynamic system that changes quickly,” says MacLeod. How can producers store more carbon in their soil? Managing the soil Soils that are undisturbed and remain covered by plant matter tend to sequester more carbon. “The best management systems for soil carbon are the ones that we don’t touch. If you think about an alfalfa stand on a dairy or beef operation, you plant alfalfa and leave it for four years,” says MacLeod. “For four years that plant grows two feet above the ground and the roots grow two feet into the ground. Then it gets cut, and then it grows again, and the roots grow again. That may be 12 times that the plant has grown and pushed that carbon into the soil. “Now you are moving to a corn silage crop. Option 1 is to terminate the alfalfa crop and no-till corn directly into the sod. You open a narrow slot Balanced fertility maximizes above and below-ground biomass. Tracy Miller photo
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