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Dr. Kate Susman Explores Soil, Plants and Why It all Matters to Our Health
More farmers and producers who have invested time, labor and money in land that has been distressed by years of chemical farming are beginning to test their food for nutrient value and density. They hope to prove scientifically what we all have intuited: farming methods that promote the health of the soil and the biodiversity above it produce food that is healthier for humans than conventionally grown.
However, what those food testers are discovering is that a myriad of factors can influence a given test result and those factors cannot yet be easily teased out. What's more, as network-scientist Albert-László Barabási, says: "‘Our understanding of how diet affects health is limited to 150 key nutritional components....these represent only a small fraction of the biochemicals present in our food. … There’s also a vast supporting cast of micronutrients: minerals, vitamins and other biochemicals, many of which are only present in minuscule quantities, but which can still have profound health effects."
Clearly the emerging scientific exploration of this "nutritional dark matter," as Barabási has coined it, will be exciting to report on and holds great promise. Yet, wherever that exploration takes us, we need first to understand the bottom line: healthy soil is where that vital "supporting cast of micronutrients" lives. Nurturing the soil where we grow our food is the best way we can be sure that those nutrients are getting into the food we eat.
Dr. Kate Susman, professor of Biology and Environmental Studies at Vassar College, begins here with a deep dive into what we now know about healthy soil, how soil is degraded by added chemicals, how it is restored, and why it matters. She'll be writing more in the coming months about how and why plants grown in healthy soil have so much to offer for our health.
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What is healthy soil and why does it mattter?
Dr. Kate Susman
We all know the expressions. Dirt poor, dirt cheap. We use these disparaging terms for a reason: dirt is basically dead matter. It does not support life.
A lot of the soil in our region has been degraded into dirt by years of industrial chemical farming. The good news is that more and more of our farmers are committed to restoring that dirt to healthy soil.
But before we talk about this great ongoing restoration project in our region and the regenerative communities growing up around it, we need to define what healthy soil is—to the extent that we know at this moment in time—and why it matters. It’s an exciting inquiry that science is only just beginning to reveal: how the life in the soil, most of it invisible to us, helps plants load up on the essential nutrients and flavor that feed our palates and provide a foundation for our health and well-being and that of the planet.
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The science of healthy soil
Soil science is a relatively new field, and even newer is the study of how soil affects plant, and thus human, health. Soil scientists have learned a lot over the past 20-30 years about the complex ecosystems that exist in the soil, how plants participate in those ecosystems and how plants respond to changes in soil health. A new picture is emerging of the many ways plants communicate with one another and how they communicate with the life in the soil. A new understanding of the powerful interactions between plants and living soil, interactions that even influence the weather, has led farmers and environmental scientists to forge new partnerships dedicated to restoring the health of soil systems, not just in agricultural settings, but in surrounding forests, streams and water systems.
The word regenerative agriculture is a term that has been stretched to mean any kind of new farming methods that lead to even marginal improvements in soil health. But for our purposes here we focus on soil health practices that also exclude the use of chemical inputs.
We define these as regenerative organic agriculture or eco-agriculture. The latter practices ensure not only healthier food, but also provide significant environmental resilience in the face of drought, excessive heat, flooding and unstable seasonal change. Industrial farming methods, on the other hand, that rely on the application of synthetic fertilizers and toxic pesticides destroy the soil ecosystem, both on farms and on the land and water around farms. The poisons in the form of pesticides and herbicides applied to artificially protect plants actually erode the plants’ own defense systems. That’s because they inhibit the organisms in the soil from producing the chemicals, known as secondary metabolites, that help plants fight against disease. What’s more, practices like harvesting crops before they are fully ripe (and then artificially ripening them with gas sprayed during trucking hundreds of miles to the grocery stores to prevent spoilage) means fewer of the natural compounds are present in the food we buy for our own diets.
Farming practices that focus on soil health are making a difference in the nutritional content of food and reducing the presence of toxic pesticides and herbicides. David Montgomery and colleagues, researchers at the University of Washington, Seattle, published a study that measured soil organic matter on ten pairs of farms from California to Connecticut. One farm in each pair was conventionally farmed (i.e., using industrial farming practices) and the other was a farm that adopted regenerative organic agriculture strategies 10 or more years before the study. The farms used different agricultural strategies, but had similar farm types and crops.
Soil organic matter is a common measure of soil health, but the investigators also measured the metabolic activity of microbes in the soil, which gives a measure of the living functioning of the soil.
Montgomery and his team found that the soil from the regenerative organic farms not only had more organic matter but also higher microbial metabolic activity, resulting in higher soil health scores. What’s really exciting about their study is that the farms using regenerative organic techniques had only been doing so for less than a decade. This means when farmers adopt regenerative organic farming practices, they can heal and restore their soil, bring it back to health, within 10 years. That’s a fast recovery!
Illustration courtesy Stuart Farr
Living soil holds onto water (so needs less irrigation), provides nutrients and minerals to crop plants and supports a diverse ecosystem. It’s the living organisms in the soil that convert the minerals from the soil into chemical forms that plants can take up through their roots and use for their growth and development. And the burrowing of earthworms and insects in the soil, along with their excrement, makes the soil spongier so that it holds water better. The crop rotation practices employed by regenerative organic farmers also introduce deeply penetrating roots that prevent extensive clumping and that aerate the soil.
Not only is the soil a healthier ecosystem on a regenerative organic farm, but it’s much less toxic because no harmful chemicals are applied.
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HOW INDUSTRIAL FARMING TURNS SOIL TO DIRT
How do decades of industrial farming transform healthy soil into dirt? Industrial farming strategies include the use of chemical inputs like pesticides and synthetic fertilizers, a monoculture approach to planting fields, along with habitual tilling and mass irrigation. Overapplication of pesticides outright kills many soil organisms and sickens those it doesn’t kill, destroying the good work done by soil microbes, nematodes and insects previously present (Bradford et al, 2020; Tsiafouli et al, 2015). Alarmingly, and contrary to what many industrial chemical companies assert, pesticides typically can remain in soil for months to many years, building up into a toxic stew that progressively debilitates soil ecosystems. These synthetic inputs demolish the ability of soil organisms to create and maintain living organic matter like microbes, fungi, arthropods and worms.
At the same time, over-tillage also degrades the soil structure that had been built up over decades by soil organism communities. Monocropping leads to uneven nutrient depletion and leaves the crop much less resilient to pests or disease. All these practices combined ultimately destroy the soil ecosystem and leave dirt in its place.
While some industrial farmers have introduced cover cropping and no-tillage to address erosion issues caused by the bare ground created by their former practices, most continue to rely heavily on herbicides to kill weeds in lieu of tillage and to kill the cover crop before the monoculture cash-crops are planted and to control weeds. Herbicides are also applied to the cash-crop to kill it all at once for a more synchronized harvest. Synthetic fertilizers continue to be applied, although perhaps in lesser quantities as cover cropping does help increase soil organic matter and nutrient recycling. Still, in a vicious cycle, plants grown in that dirt continue to be reliant on the farmer’s artificial chemicals and growing strategies. The plants grow up without their living community. They might look outwardly healthy, but inwardly lack the rich biochemistry of a healthy plant.
Illustration courtesy Stuart Farr.
Image from: www.soilweek.org.au (accessed Sept. 2026)
A CLOSE LOOK AT REGENERATING SOIL
Many in the agriculture community recognize the need to restore the soil to health for optimal crop production and healthy yields. Yet moving away from industrial agriculture approaches is costly and risky, and takes a number of years. Lacking adequate technical support, funding and policy-driven incentives, many farmers who want to transition to better soil-health practices or to wean themselves off chemical inputs entirely face many challenges and are likely to be discouraged from doing so.
However, an increasing number of farmers on the vanguard of soil health regeneration have come to recognize that soil is the gold upon which their livelihood depends and have taken the associated risks. Anyone who has toured a farm that is actively regenerating its soil will likely be eagerly invited to smell, feel, and observe the life in a fistful of it.
They will discover that soil is rich and complex, usually a deep brown in color, with lots of fibers, tiny pebbles, sand and silt particles. Often, in that fistful, there might be a worm, several insect larvae and hair-thin strands of arbuscular mycorrhizal fungi that form a dense meshwork. A tiny bit of that soil under a microscope slide with a droplet of water will reveal that it is teeming with life—single-celled creatures, teeny shrimp and copepods, nematodes and the arbuscular mycorrhizal fungi closely associated with roots, that help plants absorb nutrients like nitrogen. That soil is clearly alive and incredibly dynamic.
All this life in healthy soil is working with the plants embedded within it, forming a complex food web. The plants in the soil nurture the life within the soil and the life in the soil nurtures the plants. Soil scientists have learned a lot about what makes soil healthy, but they’ve only scratched the surface.
Scientists can name some of the organisms in soils and some of soil’s chemistry, but much less is known about the complex web of interactions between the organisms in the soil and the plants rooted in it.
The Role of Plants: Roots as a Two-Way Highway
Here is what we do know. When a plant is rooted in the soil, it looks to us like the soil is mostly just there to hold the plant steady so that it can put out leaves to absorb the light of the sun. And the soil does indeed keep the plant upright. A lot of us think that the roots are like buttresses that anchor and hold the plants in place, but they are so much more than that. We also know that roots suck up not just water but also nutrients that nourish the plant and help it grow shoots, leaves, flowers and fruit. We are now understanding that roots serve as a two-way communication highway between plants and soil communities, sending out and receiving chemical signals that foster growth and well-being of both the plants and the organisms beneath the soil surface. Turns out the plants play a huge role in the health of the soil, too.
Illustration courtesy Stuart Farr
Living soil includes the plants rooted within it.
The roots move and grow, thrusting through the soil, breaking up clumps, taking up water and nutrients and also sending out chemicals to nurture and to communicate with the other soil organisms. Chemicals like sugars and amino acids ooze out from roots and feed nearby bacteria, fungi and tiny protozoans. These organisms in turn excrete waste products like amino acids and carbohydrates that can be used by the plants. Other root chemicals act like signals that recruit the surrounding soil organisms to help the roots obtain key micronutrients like iron, magnesium, selenium and calcium. For example, some plant signals tell soil bacteria to produce molecules that help capture nutrients like iron and deliver them to plants. Still others signal soil fungi to expand their association with roots like a mesh of protection and defense against invading pests or pathogens. The larger soil organisms like nematodes feed off the bacteria, fungi and protozoa and, in exchange, burrow and explore the soil, helping the roots navigate through the network of different soil particles.
Clearly soil is an incredibly busy, diverse and interactive space and plants anchored in it are crucial to its health. The roots organize the soil and its community, and also the above-ground plant helps regulate the water both below and above ground. Water flows up and down the plant. Water is released into the air around the plant. In fact, a large community of trees can actually cause weather—rain, mist, fog, humidity. Droplets from leaves percolate back into the soil, and the shade keeps it from drying out. The above-ground plant captures carbon dioxide from the air, converting it to sugars that it uses not only to nourish itself, but also to donate to the soil community below ground. This is a healthy soil-plant ecosystem in action. A complex system that nurtures life, that regulates water availability, that moderates temperatures, that partners with plants in cycles of carbon and nitrogen capture and release.
Dirt is incapable of doing any of this.
More farmers and scientists are recognizing the key roles that healthy soil plays in Earth’s ecosystems and are increasingly aware of how toxic and harmful are the industrial agriculture practices rampant in the US and throughout the world. Efforts are underway to heal and restore soil to life. It’s not as hard as one might think, but it takes time, dedication and know-how.
Source: Growing to Give.
HOW ONE UNLIKELY ORGANIC FARMER RESTORED HIS SOIL TO LIFE
Restoring dirt to healthy soil is the mission of a new breed of farmers engaged in regenerative organic practices and strategies. Herb Young, retired from a career in the pesticide industry, is using science to prove that his investments in soil health can pay off for eaters. He knows that the key to nutrient-rich harvests is the health of the soil in which they are cultivated. He uses his farm as his laboratory and nature as his partner. As a retirement gift to himself, Herb purchased a small farm in southwest Georgia he calls “Squeeze Citrus” and set about converting it to a regenerative organic farm after an epiphany sparked by a fellow farmer about the importance of healthy soil for healthy plants. Over the past ten years, Young and his family have nourished the soil by planting a variety of cover crops around and in-between the trees. He observed how plants interact with the life in the soil and provide it with sugars and amino acid building blocks so the soil organisms can grow and thrive. He also began to add to the microbe communities in the soil by drenching it in a special “microbe tea” directly increasing the microbe diversity and sprayed the leaves of his citrus trees with their own special “microbe tea.”
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Herb Young on his Georgia Citrus Farm
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A true scientist, Young started out his journey to restore the soil by leaving some rows of trees untreated. These were his scientific controls. These trees he continued to manage with industrial agriculture techniques (synthetic fertilizers and pesticides). To find out if his regenerative strategies improved the soil’s health, he collected soil samples and sent them to labs to measure the organic matter, the soil microbe respiration (the critical measure of living organisms at work!) and even the DNA of different organisms in the soil to measure how diverse the soil community had become. He also measured the ability of his soil to soak up and retain water using a relatively inexpensive penetrometer. “It's quick and simple and gives an exact depth of penetration at a certain pressure (i.e. 200psi),” he explains. “Honestly, you could take a steel rod with three-inch increments on it, push it into the soil and get the same information.” The soil surrounding the trees embedded in his regenerated soil proved to be measurably spongier and moist. Bottom line: his strategies vastly improved the soil health and those improvements were apparent in only three to four years!
What about Young’s orchard trees? Early on, the industrially farmed trees grew taller and faster and put out fruit sooner, compared to the soil-tended rows of trees. This translated into the industrial farming “gold standard”— bigger yields. But Young looked deeper. He discovered that the trees living in the healthy restored soil were far more resilient in the face of weather events, particularly winter freezes. They were also better able to withstand plant disease. The biggest differences were in the nutritional profiles of the citrus fruit. The fruit were loaded not only with vitamins and flavor-enhancing chemicals but with antioxidants providing other nutritional and health properties, including cancer-fighting agents. And these more nutritious fruits just looked so much better than the fruit from the industrially farmed trees. As Young attests, fancy measurements or science labs are not required, simple observations and taste tests tell the story. As Young puts it, “There is an incredible difference in flavor! When doing an online taste comparison after tasting my grapefruit the flavors were explosive … there is no doubt that flavor is nutrition.”
Young is excited about the nutrient-dense and flavor-rich fruit he is growing, and which he is selling directly to customers by mail order through his website. “As a grower, I’ve found that there is a very large market for Nutrient Dense produce,” he reports.
He also recognizes that more opportunities are arising for growers like him who are focused on producing nutrient dense food.
“There IS a health crisis in America,” he says, and farming enterprises like his are meeting a societal need as it becomes more and more evident that food can be the medicine that cures that crisis.
Meanwhile, Young is helping to educate a new generation of growers through his continued exploration of science-based soil management strategies, and his offering of online courses and videos sharing his proven techniques.
WHAT HEALTHY SOIL PROVIDES
The USDA’s definition of soil health is “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals and humans.” Of course, soil does a lot to achieve that “function,” like filtering and holding water, storing carbon and nutrients like minerals, providing habitat for plants and lots of other organisms. The quality of soil (where it stands on a continuum of state of health) is determined by its physical, chemical and biological attributes.
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Nutrients and minerals
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Water retention and filtering
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Carbon storage
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Growth chemicals for plants
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Enhanced plant resistance to disease and pests
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Foundation of above-ground habitat and food webs of nature
ADDITIONAL RESOUIRCES:
https://www.osc.ny.gov/files/reports/pdf/profile-of-agriculture-in-nys.pdf
Kopittke, P. M., Minasny, B., Pendall, E., Rumpel, C., & McKenna, B. A. (2024). Healthy soil for healthy humans and a healthy planet. Critical Reviews in Environmental Science and Technology, 54(3), 210–221. https://doi-org.libproxy.vassar.edu/10.1080/10643389.2023.2228651
Fausak LK, Bridson N, Diaz-Osorio F, Jassal RS and Lavkulich LM (2024) Soil health– a perspective. Front. Soil Sci. 4:1462428. doi: 10.3389/fsoil.2024.1462428
Lehman, R.M.; Cambardella, C.A.; Stott, D.E.; Acosta-Martinez, V.; Manter, D.K.; Buyer, J.S.; Maul, J.E.; Smith, J.L.; Collins, H.P.; Halvorson, J.J.; et al. Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation. Sustainability 2015, 7, 988-1027. https://doi.org/10.3390/su7010988
Hawar Sleman Halshoy, Shwana Ahmed Braim & Jawameer R. Hama (2025) Phytohormonal regulation of root exudation: mechanisms and rhizosphere function, Plant Signaling & Behavior, 20:1, 2587486, DOI: 10.1080/15592324.2025.2587486
Feliziani, G.; Bordoni, L.; Gabbianelli, R. Regenerative Organic Agriculture and Human Health: The Interconnection Between Soil, Food Quality, and Nutrition. Antioxidants 2025, 14, 530. https://doi.org/10.3390/antiox14050530
Tsiafouli, M.A., Thébault, E., Sgardelis, S.P., de Ruiter, P.C., van der Putten, W.H., Birkhofer, K., Hemerik, L., de Vries, F.T., Bardgett, R.D., Brady, M.V., Bjornlund, L., Jørgensen, H.B., Christensen, S., Hertefeldt, T.D., Hotes, S., Gera Hol, W.H., Frouz, J., Liiri, M., Mortimer, S.R., Setälä, H., Tzanopoulos, J., Uteseny, K., Pižl, V., Stary, J., Wolters, V. and Hedlund, K. (2015), Intensive agriculture reduces soil biodiversity across Europe. Glob Change Biol, 21: 973-985. https://doi-org.libproxy.vassar.edu/10.1111/gcb.12752
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