It may come as a surprise that over 95% of “life on land” resides in soil, and that most of the energy for the world beneath our feet is derived from plant carbon. Living roots are the most energy-rich of these carbon sources. Other than the oceans and fossil fuel deposits, soils are the largest reservoirs of carbon on the planet, holding approximately two times the amount in the atmosphere and vegetation combined. The dark color of fertile soil comes from the presence of organic carbon compounds

Microbes in the vicinity of plant roots and microbes linked to plants via networks of beneficial fungi — increase the availability of the minerals and trace elements required to maintain the health and vitality of their plant hosts. Microbial activity also drives the process of aggregation, which enhances soil structural stability, aeration, infiltration, and water-holding capacity. All living things — above and below ground — benefit when the plant-microbe bridge is functioning effectively.

Soil restoration begins with photosynthesis. Imagine there was a process that could remove carbon dioxide from the atmosphere, replace it with life-giving oxygen, support a robust soil microbiome, regenerate topsoil, enhance the nutrient density of food, restore water balance to the landscape, and increase the profitability of agriculture. It’s called photosynthesis.

In the miracle of photosynthesis, which takes place in the chloroplasts of green leaves, carbon dioxide from the air and water from the soil are combined to capture light energy and transform it into biochemical energy in the form of simple sugars. These simple sugars are the building blocks of life. Plants transform sugar into a great diversity of other carbon compounds, including starches, proteins, organic acids, cellulose, lignin, waxes, and oils. Fruits, vegetables, nuts, seeds, and grains are packaged sunlight derived from photosynthesis. Significantly, many of the carbon compounds derived from the simple sugars formed during photosynthesis are also essential to the creation of well-structured topsoil. Without photosynthesis there would be no soil. Weathered rock minerals, yes … but no fertile topsoil.

Soil restoration is our ally in the fight against global warming. By capturing carbon and reversing desertification caused by severe drought, soil restoration enhances regional cooling, strengthens resilience against droughts and floods. As noted above, restoring soil ameliorates desertification, a factor that can destabilize already volatile regions. Take the unprecedented drought that precipitated civil unrest in Syria before the outbreak of civil war there. The drought was exacerbated by global warming just as were the wildfires in the western U.S. these past summers.

In a 2014 white paper, the Rodale Institute showed that regenerative organic farming could capture carbon dioxide in quantities exceeding global emissions. I was surprised to read this. The institute compared organic fields with chemical fields and found much more microbiological activity in the organic fields which led to greater carbon sequestration. In a Swiss study – comparing biodynamics with organic, there was even more microbiological activity using biodynamics methods. (The Rodale Institute supports research into organic farming. The institute was founded in 1947 by entrepreneur J.I. Rodale in Emmaus, Pennsylvania. When J.I. Rodale died in 1971, his son Robert purchased 333 acres and moved the farm to its current site in Kutztown, Pennsylvania.)

Sadly, many of today’s farming methods have severely compromised soil microbial communities, significantly reducing the amount of carbon transferred to and stabilized in soil. Over the last 150 years, many of the world’s prime agricultural soils have lost between 30% and 75% of their carbon, adding billions of tons of CO2 to the atmosphere. And over the last 70 years, the level of nutrients in almost every kind of food has diminished.

On the other hand, soil carbon can increase when farmers and gardeners maintain constant ground cover, add compost, increase microbe populations, encourage biological diversity, reduce the use of agricultural chemicals, and avoid tillage. So look no further than the ground beneath your feet for a healthy world.

I worked as a graduate student in the 1980s under Dr. Rich Bartlett, the former head of the UVM Plant and Soil Science Department. He taught me about what makes soil healthy and the symbiotic relationship between mycorrhizal fungi and the roots of plants. In Latin, mycorrhizal means fungus-root. A white fungal network called hyphae, not plant roots, is the principal structure not only for the uptake of important nutrients in the plant kingdom, but also for carbon sequestration in the soil – so critical in our world of climate disruption.
The importance of mycorrhizae is what I’ll be zooming in on in this article. First, here is some background information. Polish scientist Franciszek Kamienski gets credit for discovering in the 1880s that the fungus and plant combination was a mutually beneficial partnership.

While we still define natural habitats in terms of plants and animals, the greatest amount of biological activity and the largest diversity of species and genes, come from microorganisms including bacteria, single-celled algae, protozoans and fungi. From the upper reaches of the atmosphere to the bottom of the seas, down into the rock layers and outnumbering the stars in the known universe, microbes are literally the creatures that make Earth a living planet. Microorganisms are tiny forms of life that surround us – too small to be seen by the naked eye.

What is called a mushroom is merely the temporary structure some fungi grow to produce spores. The main body of a fungus typically consists of a network of fine-branching threads known as “hyphae” mentioned above. While you’ll sometimes see them massed together, spread like a web across a decomposing log, they’re usually hidden underground and essentially invisible to us; the individual filaments are only a single cell wide.
The network of fungal hyphae is called a “mycelium.” As it turns out, the largest known creature on Earth is neither a blue whale nor a redwood tree; it’s the several-hundred-ton mycelium of one humongous fungus that’s between 2,000 and 8,000 years old in Oregon’s Blue Mountains. By contrast, the mycelia of most species are small, but they’re as common as, well, dirt. If you pick up a pinch of soil almost anywhere, you’ll have miles of hyphae in your hand.

Although we think of fungi being most at home in deep, dank forests, they’re surprisingly abundant in open shrublands and prairies, too. The outer walls of hyphae contain gluey compounds that cause fine particles of earth to clump together on and around the threads. This process is a major factor in building soil structure and making the ground less vulnerable to erosion.

Estimates for the number of fungi species run in the millions. Mycologists have identified close to 100,000 so far. Of those, nearly 6,000 interact with plants’ roots. These are roughly divided into two types: those in which the fungus remains outside the root’s cells and those that penetrate the root’s cells. The outcome in both cases is a continual exchange.

Plants routinely face a challenge absorbing enough of certain key elements, such as phosphorus, nitrogen and potassium. Mycelium don’t face this obstacle; they produce specialized acids and enzymes that break the bonds that bind those nutrients to soil and organic compounds. Phosphorus builds up in soil more readily than the other two elements in common fertilizer mixes (nitrogen and potassium). Under a regimen of frequent, well-intended application, phosphorus can reach levels that actually discourage the formation of mycorrhizae.

Mycelial networks play a valuable role in sequestering carbon. Twenty years ago in an experiment carried on by, the Rodale Institute of Kutztown, Pennsylvania found that there was much more microbial activity in organic soils as compared to conventional chemical soils. They concluded that the solution to global warming was right beneath our feet. In 2015, the Institute produced a White paper stating, “we can sequester more than 100% of current annual CO2 emissions with a switch to widely available and inexpensive Regenerative Organic Agriculture practices.

The advent of tillage and deforestation released excessive amounts of carbon dioxide from our soils. Remember the disastrous effects of the “Dust Bowl” in the 1930s. The Plough That Broke the Plains was a documentary about what happened to the Great Plains of the United States when a combination of farming practices and environmental factors created this disaster.

Research has found that heavy or frequent tilling and the use of chemical fertilizers and soil-applied fungicides suppress beneficial microbes, including fungal mycelia. The problem worsened when we became dependent on fossil fuels to power our lives. Another destroyer of mycelia is Roundup - the brand name of a systemic, broad-spectrum glyphosate-based herbicide originally produced by Monsanto, which Bayer acquired in 2018. Glyphosate is the most widely used herbicide in the United States and has a strong connection to cancer deaths.

Regenerative organic agriculture for soil-carbon sequestration is tried and true: Humans have long farmed in that fashion, and there is nothing experimental about it. One of the Organic farming practices includes the use of compost especially when animal manures are added to the piles. Other practices include light tilling, weeding and mulching.

More advice is to avoid empty beds by keeping plants, whether food crops or cover crops growing at all times. Summer cover crops include oats, beans, buckwheat and annual rye. Plant hairy vetch in September and cut it before it is in full flower. In fall, plant winter rye. All of these plants have extensive root systems and readily harbor mycorrhizae. Cover crops of grass-and-legume blends along with compost help to retain a healthy mix of fungi.

If we are going to save the planet from ongoing global catastrophes including droughts, wildfires, the acidity of the oceans and flooding, let’s begin with how to sequester carbon in the soil and provide nourishment to the world of mycelium.

In soil, organic matter consists of plant and animal material that is in the process of decomposing. When it has fully decomposed it is called humus. Healthy, fertile soil is a mixture of water, air, minerals, and organic matter. Humus is important for soil structure because it holds individual mineral particles together in clusters. Ideal soil has a granular, crumbly structure that allows water to drain through it, and allows oxygen and carbon dioxide to move freely between spaces within the soil and the air above. The living microbial biomass includes the microorganisms responsible for decomposition (breakdown) of both plant residues and active soil organic matter.

Of all the components of soil, organic matter is probably the most important and most misunderstood. Organic matter serves as a reservoir of nutrients and water in the soil, aids in reducing compaction and surface crusting, and increases water infiltration into the soil. Yet it's often ignored and neglected.

Soil organic matter is the fraction of the soil that consists of plant or animal tissue in various stages of breakdown (decomposition). Most of our productive agricultural soils have
between 3 and 6% organic matter. I was once asked to study a soil in Benson, Vermont and I was surprised to learn it was at 7 percent. The soil had not been tilled for many years and was damp.

Many times we think of organic matter as the plant and animal residues we incorporate into the soil. We see a pile of leaves, manure, or plant parts and think, "Wow! I'm adding a lot of organic matter to the soil." This stuff is actually organic material, not organic matter.

So what's the difference between organic material and organic matter? Organic material is anything that was alive and is now in or on the soil. For it to become organic matter, it must be decomposed into humus. Humus is organic material that has been converted by microorganisms to a resistant state of decomposition. Organic material is unstable in the soil, changing form and mass readily as it decomposes. As much as 90 percent of it disappears quickly because of decomposition.

Organic matter is stable in the soil. It has been decomposed until it is resistant to further decomposition. Usually, only about 5 percent of it mineralizes yearly. That rate increases if temperature, oxygen, and moisture conditions become favorable for decomposition. It is the stable organic matter that is analyzed in the soil test.

Maintaining Soil Organic Matter - Building soil organic matter is a long-term process but can be beneficial. Here are a few ways to do it.

Reduce or Eliminate Tillage - Tillage improves the aeration of the soil and causes a flush of microbial action that speeds up the decomposition of organic matter. Tillage also often increases erosion. No-till practices can help build organic matter.

Reduce Erosion - Most soil organic matter is in the topsoil. When soil erodes, organic matter goes with it. Saving soil and soil organic matter go hand in hand.

Soil-Test and Fertilize Properly - Proper fertilization encourages growth of plants, which increases root growth. Increased root growth can help build or maintain soil organic matter, even if you are removing much of the top growth.

In November of 2020, I spread year-old compost in my community garden in the Intervale in Burlington. I love the feel of a handful of rich, dark compost. I call it “Black Gold.”

One handful contains more microorganisms than people on Earth, from the tiniest microscopic decomposers to nutrient recycling nematodes to soil-moving earthworms. These creatures use carbon-rich organic matter as energy and, in the process of eating, release valuable nutrients such as nitrogen into the soil.

They also help trap carbon underground as they turn everyday waste products, such as food scraps and manure, into fertile humus in your garden. Compost is also useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover.

Brown and green waste
What is “Black Gold?” Compost is decomposed organic material, such as leaves (brown), fresh grass clippings (green), old plants (brown), manure (brown and green) and fresh kitchen waste (green). It provides many essential nutrients for plant growth and therefore is often used as fertilizer and soil conditioner.

Compost improves soil structure so that soil can easily hold the correct amount of moisture, nutrients and air. It improves the texture of both clay soils and sandy soils, making either type rich, moisture-retentive, and loamy.

It takes a period of months and up to a year for the materials to break down into humus. It depends on the ingredients in the pile and how many times you turn it. I attempt to turn my piles at least once. More on heating, moisture, aeration and smell below.

I’ve been making compost a long time. I starting working at Hill and Dale Farm in Putney in the spring of 1969. We made compost in 100-foot-long windrows from cow manure mixed with bedding material. Compost made from animal manures is higher in nutrients and quality than those from vegetable scraps, hay and other organic materials. By the way, the nitrogen produced in the piles comes from cow urine. I use my urine mixed with water and pour it on my compost piles like I did on the solstice.

The Carbon to Nitrogen Ratio
The course of decomposition of organic matter in a compost pile is affected by the presence of carbon and nitrogen. The C:N ratio represents the relative proportion of the two elements. A material, for example, having 25 times as much carbon as nitrogen is said to have a C:N ratio of 25 to 1, which is an ideal ratio in a backyard compost pile. The ratio composting animal manure and bedding material is 12 to 1.

If there is too much carbon, decomposition slows when the nitrogen is used up and some organisms die. I have found over the years that, in many backyard compost piles, there is too much carbon, and the pile doesn’t heat up.

Heat, moisture, aeration and smell
The Four Greek Elements: fire, water, air and earth.

The first stage in the breakdown in the compost pile is fire. The optimum temperature range is 135° to 160° Fahrenheit during the heating stage. You’ll burn your hand if it’s too hot in the pile.

The next stage is water. The amount of moisture is also critical in a pile. It should be damp but not wet. Use your hand to check this out. Make sure to aerate the pile by turning it. When the compost is complete, it should smell sweet. Use your nose. I once knew a gardener who tasted well-composted manure. Hmm!

To summarize, composting takes place as a multi-step, closely monitored process with measured inputs of water, air, and carbon- and nitrogen-rich materials.

The decomposition process is aided by shredding the plant matter, adding water and ensuring proper aeration by regularly turning the mixture when open piles or “windrows” are used. Fungi, earthworms and other detritivores further break up the material. Aerobic bacteria and fungi manage the chemical process by converting the inputs into heat, carbon dioxide and ammonium.

Understanding how to make and use compost is in the public interest, especially today as the problem of waste disposal grows. So start now! Save the environment and build your own compost pile.

And remember that, without compost, soil would be dirt, the stuff you drag into your house when you forget to take off your shoes. Soil, on the other hand, is our life support system. It anchors plant roots, creates habitat for millions of critters, filters water and holds nutrients.