Quite likely, we’ve all given thought to how we might manage our land in the best manner to be as productive as possible, while helping to protect the environment from harmful chemicals and to limit nutrient loss to adjacent streams. But have you considered that how you manage your land might be equally important in leading the fight against climate change? How might this be possible when you usually hear that overgrazed land around the world could be one of the leading causes of land degradation?
If your pastures are optimally stocked and animals are moved to fresh pasture frequently (allowing a long recovery period), you are off to a good start. The grasses, legumes, and forbs you are growing are able to collect abundant energy from the sun and convert the carbon dioxide in the air into simple sugars that are converted into biomass by the growing plants. Much of the carbon in that fresh forage will in turn be consumed by grazing cattle or other livestock. But what happens to that carbon in forage tissue? A good portion of it will be digested in the rumen and a relatively small portion of it will be used to grow calves, maintain brood cow health, or produce nutrients for gestation and milk. What is not digested goes through the cow and back on the pasture.
They say “feces happens”, right?! Yes, and in this case it is a good thing. Products from rumen digestion, as well as the unused and trampled forage left behind become a source of energy and nutrients for the soil herd in the ground. Indeed, the herd includes earthworms, dung beetles, other insects, and a whole lot of bacteria and fungi (soil microorganisms) that are too small to see. When you adequately feed the soil herd by leaving behind sufficient residual forage mass after grazing, you keep the ground covered and protect plant growing points. When the plants are periodically grazed, root-derived carbon is also released into the soil. Both residual forage mass and root growth and decay provide the soil with carbon that is transformed into soil organic matter by soil microorganisms. Soil organic matter contains 58% carbon by weight, so carbon once in the atmosphere as carbon dioxide can be stored for long periods of time in the soil as organic matter. How much carbon can be stored in soil? Well, that’s a topic that many soil scientists are getting interested in and research is being conducted across the country to better understand it. The results might surprise you and they might make you realize that your farm management could be helping your country reduce its carbon footprint and fight against the threats of climate change!
Recent research on pastures throughout North Carolina and surrounding states (Franzluebbers and Poore, 2020) suggests that improved grazing management compared with conventional management led to 26% greater organic carbon concentration in the top 4 inches of soil. This research was carried out with sampling mostly on private land with collaboration from livestock operators that had adopted rotational stocking and fall stockpiling as improved approaches, as compared with continuous stocking and hay harvest in more conventional management. A number of other factors influenced soil organic matter, soil biological activity, and nutrient cycling. First, as pastures aged, they stored progressively more organic carbon in soil. Second, soils with more clay had greater potential biological activity and soil organic carbon than soils with more sand. Finally, increasing elevation from the Atlantic Coast to the Appalachians slowed decomposition and allowed greater soil organic carbon accumulation.
This study also showed that management can play a major role in how much carbon is stored in soil. A key factor that was not measured in this particular research was how deep the change in soil carbon might be occurring. This is an avenue of additional research that is being explored now. We will learn more in the future, but for now, keep up the good work by managing your pastures to store more carbon in soil so that our country can lead the fight against climate change from the ground up!
Engaging farmers in practical research on their farms has led to improved understanding of how grazing management impacts soil carbon and nutrient cycling. Pictured is Mike Jones, farmer in Surry County, NC and current President of the NC Forage and Grassland Council.
Dr. Alan Franzluebbers is a Soil Ecologist with USDA-ARS working in the Department of Crop and Soil Sciences at North Carolina State University.
The Alliance for Grassland Renewal is a national organization focused on enhancing the appropriate adoption of novel endophyte tall fescue technology through education, incentives, self-regulation and promotion. For more resources or to learn more about the Alliance for Grassland Renewal, go to www.grasslandrenewal.org