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Defining Soil Health
by LuAnn Rolling, District Conservationist
I’ve talked a lot about soil health over the past years, but what truly is the definition? One definition I found said, “Soil health is the vitality of a soil in sustaining the socio-ecological functions of its enfolding land.” What does that mean?
Soil health can be broken down into three elements, according to H. Henry Janzen, David W. Jansen and Edward G. Gregorich writing in Soil Biology and Biochemistry in August of 2021. The first would be functionality, which they said can be defined as, “the condition of an organism in which it performs its vital functions normally or properly.” They add that function cannot be evaluated by measuring soil composition but by observing how well its ecosystem thrives.
Their second element is vitality, which they define as, “the peculiarity distinguishing the living from the nonliving”. While soil is not an organism, it is a living system consisting of interwoven processes.
The third element is sustainability or resilience. The authors say that a healthy soil is one that supports ecosystem functioning into perpetuity. They say soil health is a perpetually moving ideal, reflecting evolving conditions and demands. It can never be documented in a momentary snapshot and must be maintained over time despite ongoing stresses and upheavals.
Fertility used to be the measure of soil - the capacity of a soil to furnish high crop yields. Over time soil quality displaced fertility which included erosion control and protecting air and water by retaining pesticides and nutrients.
Now soil health includes broader societal functions including human nutrition, climate regulation, wildlife habitat, biodiversity preservation and aesthetic appeal. All of these functions are difficult if not impossible to “measure”. Since soils persist indefinitely, a functioning soil must be viewed across both short and open-ended time periods. The authors in this article say, “A soil may be very effective in withdrawing atmospheric CO2 today, but that function will fade in time as its C stock approaches a steady state.” They also say that an elaborate DNA profile of microbial communities within the soil will not help understand better soil management strategies without also understanding their habitat. They suggest that a critical facet of soil health is to look at soil properties, tuned to the conditions and expectations of its setting, that maximize energy capture to allow for its sustainable storage and use.
To know if a specific soil is healthy it must be viewed from where it is located - a field, a forest, a garden and then ask what functions can this location support? Soil health will always be context dependent and properties conferring health will never be the same from place to place. The authors say, “In short, health has no meaning for a soil divorced from its setting; no amount of analysis can assess a soil’s health without acquaintance with its place.”
In 1938 Aldo Leopold said, “The problem, then, is how to bring about a striving for harmony with land among a people many of whom have forgotten there is any such thing as land…”. He already knew that it is essential to reconnect people to the soil in a way that promotes respect for soil, insight into its vitality and wiser ways of managing land to sustain its functions.
The authors of the article say that the continued usefulness of the term “soil health” depends, not on whether or not we can finally come up with a numerical value for “good” soil, but whether it causes us to have greater reverence for soil, understand the beneficial processes that it takes to maintain soil and then come up with wiser ways of managing soil.
