Climate change can feel overwhelming. We hear about melting ice caps and rising temperatures, and it seems like only world leaders can make a real difference. But truthfully, the soil beneath our feet is one of nature’s best tools for fighting climate change. It quietly stores massive amounts of carbon, keeping it out of the atmosphere.
Understanding Soil’s Role in Climate Change
Soil is basically a giant carbon storage system. Scientists have found that healthy soil holds more carbon than all the trees and plants on Earth combined. That’s billions of tons of carbon safely stored underground instead of being released into our atmosphere and warming our planet.
Here’s what happens: plants pull carbon dioxide from the air through photosynthesis. When plants die or drop leaves, the carbon that was stored in plants is released, either through respiration or combustion, and then goes back into the atmosphere or the soil. Soil microbes then break down this material and lock the carbon underground where it can stay for decades or even centuries.
What Makes Soil Healthy?
Healthy soil is alive. It contains billions of tiny organisms working around the clock that form a complex underground ecosystem. Soil microbial biomass refers to all these living organisms combined. They break down dead plant material and animal waste. They build soil structure that holds water during droughts. And most importantly for climate action, they capture and store carbon.
Simple Steps to Improve Your Soil:
Reduce Tilling and Digging
Every time you disturb soil with a tiller or shovel, you could be destroying microbial networks. These organisms build complex underground structures that help them work efficiently. Breaking these structures sets them back to square one.
Add Organic Matter Regularly
Microbes need food to survive and multiply. Organic matter like compost, mulch, or leaf litter provides this food. When you add these materials to your soil, you’re essentially helping to feed billions of organisms.
Plant Cover Crops
Bare soil is a missed opportunity. When ground sits empty between growing seasons, microbes starve and carbon escapes. Cover crops solve this problem by keeping living roots in the soil year-round.
Reduce Chemical Use
Synthetic fertilizers and pesticides can harm beneficial microbes in the long run. While they might boost plant growth in the short term, they often damage the soil ecosystem that supports long-term health causing greater issues down the line.
Why Test Your Soil?
You can’t improve what you don’t measure. Soil testing for climate action gives you concrete data about what’s happening underground. It shows you the current state of your soil’s health and its carbon-capturing ability.
Testing reveals your soil’s microbial biomass levels. High numbers mean your soil is actively storing carbon. Low numbers mean there’s room for improvement. You also learn about the fungal to bacterial ratio, which affects how long carbon stays locked in the ground.
How should you start? Pick one area to focus on first. Maybe it’s your vegetable garden, your front lawn, or a few raised beds. Test that area to establish your baseline numbers.
Choose one or two practices to implement. Don’t try to change everything at once. Start with something simple like adding compost or reducing how often you dig. Small consistent changes produce better results than dramatic overhauls. Track your soil’s biological data over time using the microBIOMETER® and other helpful soil tests.
Farmers across America are discovering something amazing beneath their feet. The secret to better crops and healthier land isn’t always found in a bottle or bag. It lives naturally in the soil, waiting to be awakened through smart and intentional farming practices. Soil microbial communities play a large role in soil metabolic activity and drive critical ecosystem services like decomposition and nutrient cycling.
Bacteria, fungi, and other microscopic creatures transform dead plant material into food that crops can use. Regenerative agriculture & microbes work together like partners in a successful business. When farmers treat soil as a living system rather than just dirt, these microorganisms multiply and strengthen.
How Traditional Farming Hurts Soil Life
Conventional farming methods can accidentally damage the very organisms that make soil productive and alive. Heavy tilling breaks apart fungal networks that connect plant roots. Chemical fertilizers flood the system with quick nutrients but starve the microbes that naturally produce those same nutrients.
Soil health drops when microbial diversity and abundance decreases. Farms become dependent on more chemicals to achieve the same results. It’s like trying to run a factory with fewer workers each year while expecting the same output.
Different microbes handle different jobs in the soil. Some break down tough plant materials. Others protect crop roots from diseases. Many form partnerships with plants, trading nutrients for sugars. This complexity creates a stable system that keeps working even when conditions change.
Healthy microbial communities also help crops handle stress better. During droughts, diverse soil life improves water retention. When diseases threaten, beneficial microbes compete with harmful ones, protecting plant roots naturally.
Farmers don’t need complicated systems to start improving their soil life. Cover crops provide food for microbes when cash crops aren’t growing. These plants keep living roots in the ground, which helps more microbes stay fed year-round instead of going dormant.
Crop rotation brings diversity that supports more types of beneficial organisms. Different plants feed different microbes, and varying root depths access nutrients from multiple soil layers. This natural variety strengthens the entire system.
The benefits of regenerative farming show up quickly in soil tests and gradually in farm economics. Crops access nutrients more efficiently when healthy microbial populations cycle them naturally. This means farmers are able to spend less on fertilizers while maintaining or improving yields.
Weed and pest pressure often decreases, too. A diverse microbial community supports beneficial insects and creates conditions where crops outcompete weeds naturally. This reduces herbicide needs and the labor involved in weed management.
Fungal to bacterial ratio serves as an important indicator of soil condition. Healthy agricultural soils need both types of microbes, but many farms have shifted too far toward bacteria-dominated systems. Restoring fungal populations helps lock carbon in the soil and improves overall stability, as fungi connect different plants and transport nutrients across distances that roots alone could never reach.
The science behind soil biology keeps advancing, giving farmers better tools and understanding. New microbial products target specific crop needs or soil conditions. Education and support networks help farmers adopt these methods successfully. Universities, extension services, and farmer groups share practical knowledge gained from real-world experience. This collective learning accelerates the regenerative movement.
David Purdy,, Territory Business Manager at John Deere and Soil Health Specialist, utilized the microBIOMETER® soil test in his study titled Assessment of the mircoBIOMETER Soil Biology Test for Agrovista LTD.
Background:
There is an increased level of interest in soil health and a greater demand for more analytical approaches, in particularly for soil biology, for its assessment from farmers and advisors. This short report reviews the use of a recently developed rapid on-site soil microbial carbon testing tool called microBIOMETER® using a replicated 5 year cover crop experiment.
David Purdy, Territory Business Manager at John Deere and Soil Health Specialist, utilized the microBIOMETER® soil test in his study titled Assessment of the mircoBIOMETER Soil Biology Test for Agrovista LTD.
Background:
There is an increased level of interest in soil health and a greater demand for more analytical approaches, in particularly for soil biology, for its assessment from farmers and advisors. This short report reviews the use of a recently developed rapid on-site soil microbial carbon testing tool called microBIOMETER® using a replicated 5 year cover crop experiment.
Location:
The experiment was carried out at the location of the Agrovista LTD. trials site is near Lamport in Northamptonshire about 8 miles north of Northampton in the UK. It has a longitude of 52.372234, and latitude of -0.874273. The field site history is of arable farming rotations on a slightly southerly sloping topography.
“The tests, although time consuming, provided an “in field” test that when conducted well seems to suggest it is a reliable, consistent, replicable, and relatively simple test to evaluate soil biological activity.” – David Purdy
This is an abridged version of Dr. Judith Fitzpatrick’s talk at last December’s Acres U.S.A. Eco-Ag conference. Article also featured in the April 2022 issue of Acres U.S.A. magazine.
When a grower first goes organic, they often have one field that’s organic and, right next to it, a field that they’ve been farming conventionally. They run out and test the soil for microbial biomass, and then they write to us and say, “I don’t have any more microbes in my organic field than had in my conventional field.” Why?
It’s because, as a farmer, you have a big, big job when you transition to organic. What you have to have is microbes working for you, and they take time to re-establish after years of conventional farming. We’re all familiar with the food web, but what the conventional pyramid doesn’t communicate is that the microbial base constitutes greater than 95 percent of the food web biomass because all the life above it depends on this food source.
You can view the plant-microbe relationship as a marriage. Each one has a role to play, and they support each other. The plant delivers 30 to 50 percent of the food that it makes to the microbes in the soil in an organic system, and the microbes synthesize and mine the nutrients in the soil and deliver them to the plant. This is a marketplace.
A key player in the marketplace are the arbuscular mycorrhizal fungi. Arbuscular means “room” or “little house.” Arbuscular mycorrhizal fungi actually live — part of them — inside the plant. Outside of the plant they’re picking up phosphorus, nitrogen, potassium, sulfur, and other minerals. When these are transported to the plant, the fungi trade them for the carbon they need — 50 percent of the dried weight of microbes is carbon, as all organic molecules are carbon based.
Arbuscular mycorrhizal fungi hyphae also connect them to other plants. This is especially true in forests. Scientists have shown that arbuscular mycorrhizae will give more phosphorus and other minerals to the plant that gives it more carbon. And they are key players in disease prevention.
The plant-microbe symbiosis is a sophisticated system based on needing each other. In conventional agriculture, you feed the plants directly with chemicals; the plant does not need microbes, so it does not nurture them, and you have a microbe-deficient soil. Microbes do more than feed the plant the nutrients you used as fertilizer, or that they manufacture — they build soil structure, support plant immunity and mine micronutrients in the soil for your plant. When you don’t rely on chemicals, you’re going to be reliant on microbes to feed your plant, and the microbes will build soil structure, mine nutrients for the plant and protect them from pathogens.
We have recently discovered that rhizophagy is an important way that bacteria deliver nutrients to plants. The plant puts out exudates that bring in the microbes it wants to inhabit the rhizosphere. These microbes are often referred to as plant-growth-promoting bacteria because they stimulate plant growth. Bacteria in the rhizosphere enter the root. As they migrate up the root, about 40 percent of their nutrients are extracted by the plant. In return, the plant gives them carbon and forms root hairs through which the bacteria can reenter the soil. Dr. James White has shown that plants that do not have these plant-growth promoting bacteria do not form these important root hairs. He has also shown — and other studies have shown too — that a plant can get 40 percent of its nitrogen, as well as other nutrients, through rhizophagy.
Conventional farming replaces the need for microbes by giving plants NPK, etc. What happens to your plant when you do this? If you put down nitrogen, you do not get the same amount of root growth as when the plant and microbes have nurtured the root. If the plant doesn’t need nitrogen, it doesn’t feed the microbes as much. It’s devastating. When you consider putting on nitrate and ammonium, think about the effect on the root and all the important contributions roots make to soil — e.g., plant stability and fertilizer.
When you go organic, or when you’re maintaining it, your job is to continue to either improve this broken marriage or to maintain it. If the land has been farmed conventionally, you have four big problems: poor soil, a decimated microbial population, a poor crop-microbe fit, and depleted soil organic matter or carbon stores — 50 percent of the carbon that was stored in our soil has been lost.
We’re stuck growing our microbes in a poor soil environment in which they’ve lost their homes. Microbes live on sticky pieces of soil and within aggregates. They multiply inside the aggregates, and in there they are protected from grazers like amoeba. These aggregates are formed by tiny roots and by fungi, providing microbial homes. They are what makes a healthy soil structure, because they allow soil to hold air and water and to prevent erosion. They’re not steady; they can go away if microbes and plant are not continually rebuilding them. In soils that have been chemically treated for years, you do not have good soil structure — you have eroded, compacted soil.
BUILDING SOIL STRUCTURE
How do the microbes build soil structure? A microbe has to attach to the soil — otherwise it will wash away, the same way chemical nutrients do. So, it secretes sticky substances. The best sticky substance is made by fungi. It’s called glomalin. These sticky substances are nutrient rich, and they allow the microbe to stick to the soil. They are very long lasting — even after the microbe dies, these sticky substances stay around, and they cause the particles of soil to stick to one another. They’re what build your soil structure. By increasing your microbes, you’re increasing your soil structure.
Depleted carbon stores also reduce food security for microbes and, by extension, plants. Microbes make soil organic matter (SOM) from the plant material. Plant roots are a very rich source of SOM for soil. That’s why cover crops work so well — they not only nurture microbes and protect the soil surface from erosion, but they’re great for building SOM. The dead roots are an excellent food source for microbes, and the digested material becomes attached to mineral surfaces. When the microbes die, they also become humus.
It’s a relatively recent understanding that 60 percent or more of the SOM that we call humus is actually the bodies of dead microbes. The rest is material that’s been digested by microbes. So, it’s going to be impossible to increase your SOM without increasing your microbes. Increasing your SOM is important because the SOM is the best indicator of plant health.
You can put down a meal like sugar— a lot of the amendments you put down are basically just sugars — that will cause the microbial population to expand. But if there’s not backup food sources from the generations of microbes that came before, or a slowly digestible fertilizer source, the population quickly dies off. It’s like giving a kid candy — it’s not going to build muscle. The amount of microbial biomass correlates very closely with the SOM that’s available to the microbes in that soil, in both humus and recently supplied fertilizer foods.
The number of bacteria in the rhizosphere is going to be much higher than in the surrounding soil, but it’s the surrounding soil that you measure most of the time. I call that the suburbs. The suburbs reflect much of what’s going on in the rhizosphere, but with a lower population. In a bare field, the microbial population is way down. This is one of the reasons that your cover crop is so important. Cover crops help maintain the plant-microbe process, so the microbial population is maintained and SOM increases to provide the carbon and other nutrients that your plant’s microbes will need for the coming cash crop.
Bacteria have about one one-thousandth of the DNA that we have. So, for most of their functions, they’re depending on molecules produced by other microbes. Every cell in your body — every cell in the world — is a gated community. Air and water can go in and out, but absolutely everything else has a receptor. Your microbes are very picky eaters because they have few receptors and few enzymes for digestion. We can only grow about 1 percent of soil microbes in the lab because you have to find out exactly all the different things that you have to provide for that one particular bacteria to grow.
If I take soil and plate it in the lab, the next day I might see one or two colonies. But if I let it go a couple of months, many different colonies start popping up — one today, another tomorrow — all different colonies. One needs another. We don’t yet know the nutritional requirements of all these different bacteria. What we do know is the system is self-sustaining, as one microbe starts to flourish and creates the food another microbe needs; then that microbe starts flourishing, and the chain continues. That is why a soil amendment that feeds the microbes is so effective. They start the process and allow the natural system to start to rebalance itself. This is also why microbial diversity increases as microbial biomass increases, as evidenced by the fact that the fungal population tends to increase in step with the increase in microbial biomass.
Just because you put down a bacteria in the soil doesn’t mean that it has a community that can support it. It’s like taking anybody with one talent and putting them in a community. There may not be the need for their talent, and there may not be the resources that they need in order to function.
Another thing that we’re just beginning to learn is that many currently used cash crops have been bred to thrive under conventional farming practice and have lost the ability to effectively communicate with microbes. This further complicates the transition to regenerative farming and encourages farmer dependance on chemical fertilizers. Now scientists are crossbreeding with some of the older species and increasing the synergism between the microbe and the plant. They’ve been able to get nice increases in productivity when they do that, because regenerative growers are dependent on microbes to deliver the nutrients the plant needs.
When farming chemically, the lab provides an NPK formula. For implementing regenerative farming, you guys have been the pioneers and the researchers, because there is no formula for this — every healthy soil develops a population of microbes that is unique to your soil, climate and crops. Even down the road from one another, people have different soils. To a great extent, you farmers are the underrecognized regenerative researchers.
DIFFERENT MICROBES FOR DIFFERENT SOILS
It’s amazing what different cover crops do for different soils. A group in New York City planted different cover crops in 6-inch pots of soil from an abandoned lot, where the microbial biomass was very low. After three weeks they looked at the soil microbial biomass. There was a tremendous difference in the number of microbes that could be measured in just a few weeks. Clover gave almost a 600 percent increase. In this case, wheatgrass was much lower. We’ve done studies with the University of Tennessee; there, hairy vetch was the winner. They have different soil, and they were growing cotton.
The point is that your soil is going to react differently with every cover crop. I spoke one time at a potato conference, and I said, “We really should have a place where farmers could just send in a piece of their soil and say to the lab, ‘I want to grow this; what cultivar should I use, and what cover crop should I use, and what actually works with my soil?’” At the end of my talk, everyone said, “Where do I send my soil?” I said, “Unfortunately, there is no place you can send your soil to have that work done. But it would be nice.” Also, as farmers know, growing and experimenting inside is not the same as outside.
ESTABLISHING OPTIMAL MICROBIAL BIOMASS
A lot of people ask us, what affects the microbe level I am measuring? Number one is moisture. We only test soils that are fresh, field-moist samples. They will contain as much as four times as many microbes as dried soil. If we revive a dried soil in the laboratory, the population of microbes is different in composition, and often in biomass, than that same population in field-moist soil. We especially see a big difference in the fungal-to-bacterial ratio because fungi seem to be more susceptible to drying out. We developed our on-site test at the suggestion of James Sottilo, one of our founders, who said, “I can’t send my samples to a lab. It’s like sending a body to a lab and asking how it’s doing after it’s been three days in the U.S. Post Office. And I need an answer now —not in two weeks.”
Microbe levels are also dependent on adequate nutrient levels, favorable pH and low compaction. If you have compacted soil, there’s not enough oxygen in it, so your microbial biomass will be low. Any disruption, like tilling, can greatly affect your microbial biomass. Temperature, salt and other chemicals affect microbial diversity and your crop. Other experiments have shown that as temperature goes up, microbial biomass goes down — but respiration, which indicates activity, goes up.
Microbial biomass varies over the season. Different test systems give quite different results, so you should stick with one system for monitoring. Interestingly, in spring, when the plant first wakes up and puts out a big boost to stimulate the microbes, we see a doubling of the microbial biomass, which then drops down. That’s called the priming effect. A fertilizer can also have a priming effect.
It is very important that after a priming effect there is sufficient food for the microbes that have been stimulated. For most soils, this requires that the fertilizer have the correct C:N ratio for the soil and crop. A fertilizer with too high a C:N ratio will boost respiration, which means the carbon is being released as CO2, but it will not allow the microbes to store the C in the organic carbon compounds that the microbes need to nourish the plant and build soil structure.
Microbial respiration — the amount of carbon dioxide released by a given weight of soil — is a measure of microbial activity and is not necessarily correlated with microbial biomass. These two measurements tell you two different things. The most important information you can get from testing is what is called the metabolic quotient (q). The q number = respiration / microbial biomass. If respiration of a given microbial biomass is higher than it should be, your fertilizer is being released into the air and not helping your microbes and plants to grow. Luckily, the fungal-to bacterial ratio correlates almost perfectly with q and tells you that you’re building fertility, not releasing it into the air as CO2.
In an organic or sustainable system, you’re entirely or largely dependent on the microbial community for immunity to pathogens. I can’t emphasize enough that the immune system of the plant is microbial. If the plant gets an infection of its leaves, it sends a message to the
root to bring in the bacteria that makes the antibiotic that it needs to fight that infection. If you don’t have those microbes, you can’t do that. Plants, like people, need to be exposed to a whole variety of microbes — not just good microbes. A huge study in Europe showed that organic farms required 97 percent fewer pesticides of any sort. What a gain in cost savings and food health!
Plants need to be exposed to and learn the ways of bad microbes. Organically grown plants develop 2,000 antioxidant compounds that are not in plants that are grown non-organically with chemicals. Those antioxidants protect the plant and when ingested provide protection against inflammation, cancer, etc. In addition, it is these antioxidants that plants make to defend themselves against disease that give microbially nourished plants the flavors that make them so much more desirable.
Your plant is also dependent on microbes for its required minerals and nitrogen, for digesting litter to increase soil matter, for providing information about soil conditions that allow the plant to adapt and for creating soil structure that increases water holding capacity — when you have an adequate microbial population, you increase your water holding capacity by 50 percent. Microbes also increase soil structure — protecting soil from erosion while building soil organic matter. It is important to point out here that soil organic carbon is what is measured, but it is stored in SOM — molecules containing NPK and all the other nutrients plants need.
The key to transitioning, then, is to provide the environment that will allow your microbial community to rebuild itself. There’s no formula for it. The right formula will depend on your soil, your climate and your crops. We know that the microbial community can do this by itself, given the right foods and opportunity. And you can tell if you’re going in the right direction by measuring microbial biomass and fungal-to-bacterial ratio.
In learning how to develop healthy soil for healthy plants and people, Frans Plugge of New Zealand discovered the importance of increasing the fungi population in his garden and this led him to microBIOMETER®.
“The microBIOMETER® soil test makes measuring the fungi to bacteria ratio so easy,” Frans said.
To promote the benefits of soil regeneration, Frans has started the community street garden using the principles of regenerative agriculture; minimizing artificial fertilizers, pesticides and herbicides. Frans plans to take regular measurements of the fungi to bacteria ratio using microBIOMETER® to monitor his progress as well as create a great discussion point with members of the garden community, therefore, contributing to a healthy plant community.
Some of the microBIOMETER® results Frans shared with us for his home garden and compost:
The first photo pictured here is a bare clay strip that Frans forked loose but did not turn. He added a thin layer of garden compost along with a layer of soil sowing in ten different species of autumn crops; legumes, grasses, and cereals. Then he planted brassicas into the garden (second photo).
Over the years, Frans typically added compost and dug in green crop in the main vegetable garden, but had not had great success in yield. This autumn in the area the microBIOMETER® sample was taken from, he planted an autumn cover crop of 7-8 different species and a selection of brassicas amongst them. The idea is when the cover crop begins to go to seed, they cut at root level and drop as mulch (third photo). Frans is hoping they can stop digging in an effort to build up healthy soil organisms.
Frans’ conclusions related to New Zealand’s potential to reduce its carbon footprint:
About Frans:
