Dr. Maria Silveira is a soil scientist at the University of Florida’s Range Cattle Research and Education Center in Ona, Florida. Recently, she presented the fifth webinar in an 11-part series called Grazing Land Management and Soil Carbon. The topic of Dr. Silveira’s talk was “Challenges and opportunities to increase soil carbon in subtropical grazing lands”. The carbon cycle is an important subject for Go Natural Education, and we want to make understanding it accessible to everyone.
New to soil carbon? This video with Gil Daigneau, founder of Go Natural Education, covers the basics of carbon in the soil and in the atmosphere.
What Happens When You Lose Soil Carbon?
Dr. Silveira began her talk by stating that a loss of just 1% of the organic carbon sequestered in the top 10 centimeters (cm) of grazing land soils would equal all the carbon emissions from agriculture. If that scenario strikes you as impossible, consider that soil organic decomposition is high in the warm, humid climate of the southeastern United States. There’s a lot of photosynthesis, but also a lot of decomposing organic matter.
Sometimes, it can be difficult to convince people about the value of sequestering carbon in the soil so that it’s not in the atmosphere. The reasons range from farm and ranch economics to a lack of interest or incentives in land management practices such as no-till farming. There’s also information overload. As Dr. Silveira explained, Googling “pasture soil carbon management” yields 4400 web results.
Among soil scientists, there are challenges as well. For starters, there’s a lack of uniformity in how soil organic carbon is studied and reported. Different scientists look at different soil depths and layers. They also use different analytical methods and perform different calculations. They even report soil organic carbon in different units of measure. At a time when a lot of people don’t trust scientists, none of this helps.
Sand, Water, and Fire
Dr. Silveira’s presentation focused mainly on Florida, where the soil is approximately 99% sand. There’s little to protect soils like ultisols against degradation, and some land management practices that work well in other parts of the country won’t work in the Sunshine State. The hurricanes that hit Florida can put rangeland under water, but these areas are also resilient enough to continue to be a carbon sink.
Interestingly, grassland fires in Florida aren’t as catastrophic as you might expect. Vegetation can recover its photosynthetic capacity in just 60 days following a prescribed burn, Dr. Silveira explained. Even in a year when fire occurred, rangeland can still serve as a carbon sink. Fire can improve soil’s nitrogen content, but only for a short period of time. By the second year, the nitrogen gains are gone.
What would it take to increase interest in soil carbon sequestration, especially among farmers and ranchers? Dr. Silveira suggests “long-term, coordinated research to understand and predict the benefits and tradeoffs”. She also recommends the expansion of financial incentives to encourage ranchers to adopt land management practices that both sequester carbon and improve soil quality.
Here at Go Natural Education, we’ll continue to do our part in raising awareness.
Additional Reading
Publications by Maria Silveira