21 Story Idea? Email Paul.Nolan@Farms.com Better Farming | April 2024 Carbon Sequestration above, and you can use multiple ways to store carbon at the same time.” MacLeod’s description of sequestration refers to organic carbon, but Chiang’s and Santos’s research focuses on soil amendments that sequester inorganic carbon. MacLeod also categorizes carbon in “living” and “decomposing” fractions. He 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. Within a wet year in Ontario soils, you may have more carbon sequestration, but might also have more microbial activity that releases more,” 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, the 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 and drop corn seed in, and the corn roots grow through now-dead alfalfa roots, and that carbon stays intact.” When intact, these root systems also allow for greater water-holding capacity during drought without waterlogging in wet years, allowing for crop resilience. “What often happens is we have four years of alfalfa and all that carbon in the root mass, and we come in with tillage and break that sod down.” MacLeod says that the introduction of oxygen to soil during tillage increases microbial activity, converting stored carbon back into carbon dioxide and releasing it into the atmosphere. He recommends leaving tillage equipment in storage as often as possible, and if tillage is necessary, using a minimum tillage approach. His three recommendations for maximizing soil carbon are: 1. Minimize tillage wherever possible to avoid disturbing stored carbon. 2. Include perennial forages in the rotation. This is an opportunity to work with livestock producers or take advantage of the forage export industry. 3. Balance soil fertility to maximize biomass production. John Cross of a7 Ranche, near Nanton, Alta., uses a planned grazing program to maximize soil carbon and pasture productivity. “Carbon sequestration is an outcome of healthy plants. If you have healthy plants, you’re likely going to have more carbon in the soil,” says Cross. “So it’s more like working at having a healthy landscape, and a byproduct of that is more than likely more carbon in the soil.” With the holistic planned grazing approach to land management, Cross says it’s essential to commit to it. “We really do it. Lots of people say they do it, but they really don’t,” says Cross. “We have three herds in about 120 pastures with a 60-day recovery period and an average grazing period of a day and a half. What we try to do is have a long rest period and short grazing period. Appropriate utilization is also important. You can have long rest periods and short grazing periods, but if utilization isn’t pushing land enough, you can actually go backwards.” Cross says they have a land description for what they want their system to Increased soil carbon sequestration supports crop productivity. Emily Croft photo
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