By Hannah Birgé, PhD candidate in the School of Natural Resources and The Nebraska Cooperative Fish & Wildlife Research Unit at University of Nebraska
Most of us generally know what’s meant by “soil health”. The problems emerge when we try nailing down its specifics. What makes a soil in Nebraska quantifiably healthier than a soil in Antarctica? What variables reveal a farming practice to be destroying a soil’s health? As a land manager, how can I adjust aboveground practices to improve my soil’s health?
With so much soil heterogeneity across space and time, and so many diverse human demands and perceptions of soil ecosystem services, is operationalizing “soil health” an impossibly fast moving target? Perhaps. But the term is now commonplace in the lexicon of practitioners ranging from small town farmers to federal scientists guiding national policy. A more precise definition of soil health can shift the concept of “soil health” from where it currently resides –firmly in the abstract –so that it can fulfill its lofty potential in applied contexts. And keying in on a better definition for soil health likely matters: for producers to meet the demands of population growth by 2050, they must increase agricultural output by 70%, intensifying current agricultural operations, converting non-agricultural lands to row crop agriculture, and relying on soil in remaining non-agriculture lands to provide essential ecosystem services –all while contending with additional, interacting, drivers of global change. Yet undesirable side effects and soil feedbacks exist that, if ignored, could undermine the long-term capacity of this large-scale transition to sustain people and nature. Developing a general method that could be applied by practitioners to capture local changes in soil “health” would be an invaluable asset during this transition.
A first step towards establishing a working definition of soil health is simply to assess how its operators use the term. So I asked farmers, scientists, state and federal agency personnel, and land managers to describe soil health, in their own words. Their annotated answers are at the end of this blog.
Here are the key take homes from all of the answers: nearly all respondents recognized the central role of soil organic matter/soil carbon to soil health, and they all described a soil system with integrated physical and biological components as being “healthy”. None of the definitions mentioned a specific value or rate of change for any single variable that a practitioner could measure to better elucidate the “health” of their soil. Each one described an integrated system that gave rise to emergent properties –much like human health. Important and immeasurable. In other words, this exercise didn’t progress “soil health” towards some operationalizable metric, or even clarify the definition in a meaningful way. But it does reveal something important about how we perceive the soil as managers, farmers, and scientists. There is a growing recognition that the biological and abiotic components belowground are vastly more complex than previously appreciated, and that incorporating soil ecological knowledge into management decisions is essential for meeting long-term objectives. Stewards and scientists of the soil may be a long way from developing a general method for assessing soil health, let alone landing upon a single definition, but that doesn’t mean the exercise of trying isn’t yielding vital benefits along the way.
I first met Art Tanderup in summer 2014. You might recognize his name if you’re from Neligh, NE (pop. 1,599) or if you followed the XL Keystone Pipeline fight and Cowboy Indian Aliance, of which he was/is a vocal leader. Art and his family have a picturesque farmhouse surrounded by gently rolling rowcrop farm fields, and flanked by sturdy modern outbuildings (I should know; I hunkered down in one during a brief tornado). In reply to my query, Art sent me this over Facebook: “In an era of increasing world populations, the challenge is becoming one of increasing quality food production. That challenge begins with building soil health. The first step is to move agriculture to a no-till farming system. Along with that is planting cover crops. These practices keep carbon in the ground as the soil thrives with active worms, microorganisms, and open space for oxygen and water. The ground cover created by not tilling and cover crops creates mulch for new crops to emerge in. The mulch slows weed growth, prevents run off and keeps the soil cooler in the heat of the summer. As the cover crop roots decompose, root channels are created for the new crops. The entire process also increases organic matter in the soil. Incorporating livestock production into a no-till operation can enhance soil health.”
I also reached out to the Nebraska Corn Growers Association, and received a response from Clay Govier, a 5th generation (!) farmer who runs a corn and soybean operation with his brother near Broken Bow, Nebraska. If you haven’t had the chance to experience the beauty of the United States’ heartland (interstate 80 does not count), Broken Bow should float to the top of your list. He told us that, “To me, soil health means caring for the organisms that live in the soil as much as I care for the cash crop we're growing. Soil health means balancing the soil's minerals to give the microbes a balanced diet just as we feed ourselves a balanced diet. Healthy soils lead to healthy plants that don't need fertilizers or fungicides to survive. To have healthy soils you must have good soil biodiversity. Healthy soils grow healthy food.” Clay also captured the tension that arises from uncertainty surrounding the feedbacks between short-term crop yield gains and long term soil functioning and noted that “most farmers try their best to be good stewards of the land they farm, but are overcome with the amount of information they receive from sources (i.e. large ag, chemical, fertilizer, and seed companies)”. It’s equally true that managers of natural lands and soil scientists deal with similar uncertainty and doubt –more information about the soil doesn't always lead to knowledge or better decision-making (brief plug here for my paper and corresponding blog post entitled Adaptive Management for Soil Ecosystem Services).
I also received a response from a colleague’s father, Dave Schiltmeyer, who runs a corn and soybean operation in Elgin, Nebraska. His emailed response: “Good soil health means that I will have good plant structure from the beginning of the growing season to the end of the growing season. Good soil structure means good plant structure, which then means good water retention, and finally that turns into good yields and good test weights from my crops.”
THE AGENCY PERSONNEL/LAND MANAGERS
Back in November, Dr. Bill Shuster, Research Hydrologist United States Environmental Protection Agency, and I were discussing the conundrum of “soil health”. Bill researches how various soil types influence green infrastructure in urban settings and I was interested in how he considered soil health. After some thought, he emailed this to me: “Soil health is a consilient, dynamic state of affairs in which organic matter is of sufficient content and quality to energize nutrient cycles within a mineral matrix that itself lends support to root systems and soil fauna, and is hospitable and economical with regard to air and water fluxes.”
Scott Wessel is a private lands wildlife biologist with Nebraska Game and Parks out of Norfolk, NE. I work closely with him on my Ph.D. research to examine how hidden soil feedbacks influence management outcomes. I think about soil a lot. Scott thinks about soil more than he used to, but when I texted him to ask how he defined soil health his first reply was “did you mean to text me!?”. When I assured him that yes, I did, because soil is the literal and functional foundation of all terrestrial ecosystems, and last I checked he worked with wildlife in Nebraska, which is far from major oceans. His response, via text message: “Soil health to me is probably best defined on normal to poor scale of form and function. Are the pieces still there and functioning ‘normally’ in relation to everything else of interest to the manager? For the “everything else” group I’d guess value would be driven in most cases by perspective.”
Chris Helzer is the Director of Science for The Nature Conservancy of Nebraska. I reached out to him and we had a brief discussion about the problematic nature of the term “health” and how loosely it’s applied to so many contexts. He agreed to offer up a brief definition when I explained that my article was partly a discussion of this problem. Chris’s definition is as follows: “Soil health refers to the capacity of interacting living and non-living soil components to support diverse and resilient plant and animal communities and ecosystems.”
THE ACADEMIC SCIENTISTS
Dr. David Angeler is an Austrian scientist working in Sweden with expertise in complex systems science and the application of ecological theory to land management. I reached out to him wondering if he could deliver a punchy, quantifiable definition of soil health, and his first reply was as follows: “the term ‘health; has been debated in ecology because it is pretty vague. If there is a healthy soil what does a sick soil look like :-)))” I followed up, telling him about this piece and asking him, if he had to, could he possibly define soil health. The second time around (David is a great sport), he gave me this: “Soil health is the ecological condition of soils wherein structural and functional attributes allow for the maintenance of critical ecosystem processes, both in the soil itself and in other ecosystems that directly and indirectly depend on soils. Healthy soils are ultimately necessary for ecosystem service provisioning to humans.”
Dr. Jenny Soong is a soil scientist and postdoctoral researcher studying the effect of environmental gradients on soil carbon and nutrient dynamics in the tropics. She emailed me this reply from her laboratory in Belgium: “To me, soil health should take into account the various ecosystem services that soils provide, including nutrient recycling, carbon storage, water filtration, habitat for biodiverse biota, resistance to erosion, etc. while also taking into consideration some degree of resilience or stability. Of course that's very general! What that means in context is fully dependent in both place and time.”
When I asked Dr. Rich Conant of Colorado State University (and my old master’s adviser) what he thought was meant by “healthy soil” he told me, “You know it when you see it.” Apt!