While soil carbon is often the focus of discussion in regenerative management, it is the interface of plants and microbes that grow soil. Monitoring the microbes in the soil is therefore one more powerful tool in the toolbox toward a better understanding of land management.
After all, it’s the microbes that do a lot of the heavy lifting to bring nutrients to the pasture plants by forming mutualisms and releasing nitrogen and phosphorus from decomposing litter. This market place below ground is what fundamentally drives the production of soil organic matter, which is what creates soil humus, the material in the soil that holds carbon for a very long time.
Much of this microbial activity is driven by photosynthesis, a process that combines CO2, sunlight, and water to produce sugars and grow leaves, roots, shoots, and seeds for the pasture plants (building biomass). This biomass will ultimately return to the soil as detritus, feeding belowground biota including microorganisms. In addition, some of the glucose and other metabolites within the plant are exuded out of the roots (exudates!), further feeding the soil microbes. All of this microbial activity—eating, metabolizing, dying— contributes to the cycling of soil carbon. Microbial testing is key to a robust monitoring program. Knowing more about the microbes in the soil will help us to better understand how the pasture performs by taking a nice look under the hood. In so doing, we are able to see what, or who, is driving ecosystem function. Recently during a lecture for our interns, Chelsea Carey, Senior Soil Ecologist from Point Blue Conservation Science, reminded us that microbial composition varies across space and time. And in many cases, who is there can absolutely matter.
Chelsea spent the day with our summer interns to discuss soil science as it relates to regenerative management. Starting in the morning, she began with an overview of soil to get everyone up to speed. The latter half of the morning then ramped up the discussion by covering some key services performed by the microbes that work in concert with the pasture plants to build soil organic matter.
Afterward, we headed out to the pasture to collect soil samples for microbial testing. Specifically, we will be using DNA sequencing to determine who is in our soils, and to infer what their functions may be, in order to better understand our pasture and how we might be able to manage for our goals. It was interesting to learn that before culture independent techniques were employed, soil science was limited to only what can be cultured in a lab setting. Essentially, if a microbe didn’t grow in the petri dish (the standard of culturing microbes), it was too difficult to study. Less than 1% of microbes are readily cultured in the lab. That means over 99% of the microbes in the soil were poorly studied until recent times! From a microbial standpoint, we have an enormous amount to learn about what is actually happening in the soil.
Fortunately, technology is quickly catching up. As we continue with more microbial testing around TomKat Ranch, we will keep you posted on what we learn.