A Rap on Soil

By Mel Lions

Gardeners have always understood the value of healthy, rich soil. They take great care to nurture and develop it as a treasured asset that gets better with use. But because its mysteries lie below the surface, it’s hard to know what’s really going on down there. Before the invention of the microscope, the underground world was beyond human perception. Finally, research is giving us insights into the ground beneath our feet.

What’s being learned is turning our understanding upside down. Healthy soil, it turns out, is a habitat. It is as dynamic and biodiverse as the above-ground world, albeit on a microscopic scale. It’s teeming with life, populated by billions of living creatures of myriad varieties alive in every teaspoon. All interacting with each other, along with the roots of the plants and the decaying roots of last year’s plants. They’re breathing the atmosphere and even interacting with the gardener herself. These microbial inhabitants of the soil jungle are the secret in the sauce of successful gardening. We now have evidence that cultivating our friends beneath the surface pays huge dividends above it.

Soil’s Historic Bad Rap

Language is full of negative terms related to soil: dirty, dirt poor, dirtbag, and being soiled. Modern agriculture diminishes the value of soil, treating it as an inert medium whose value is quantified in how easy it is to plow and the chemical inputs it needs. As it turns out, commercial agricultural practices are the leading causes of topsoil loss and the destruction of the microbial habitat. Agricultural soils are nearly lifeless due to regular tilling and chemical inputs.

Our agricultural ancestors were geniuses. The invention of the plow changed the course of human history. Tilling allowed humans to grow food with profound efficiency, making cities and civilizations possible. The development of agricultural technologies and tools have been primary drivers of human invention. However, over a 10,000 year history until about 200 years ago, most farm implements were animal or human-powered. Until about 100 years ago, the only nutritional inputs were from Nature: manure, compost, and cover crops.

The industrial revolution of the 1800s introduced mechanized tillage fueled by burning carbon. The 1930s introduced petroleum-based chemicals to agriculture, and soil hasn’t been the same since. Because most land-grant colleges doing soil research primarily examined industrially farmed soils, they had no clue about how alive non-cultivated soils are, and how important soil microbes are to plant health.

Think about it: plants, soil, and microbes have been co-evolving over billions of years into symbiotic systems, each supporting the other. Replacing this process with mechanical and chemical substitutions has led to a rapid expansion of food production, but with unsustainable side effects such as loss of topsoil, loss of biodiversity, and the diminishment of flavor and nutrition from the food we eat. With diet-related diseases being the leading causes of death and illness across the globe, our food is literally killing us, and how we grow food is killing the planet.

The Difference Between Dirt and Soil

Soil and dirt are not the same. Dirt is largely composed of ground-up rocks and minerals, with a minor amount of organic matter. Depending on how moist and compact the soil is, this organic matter may be biologically inactive or only seasonally active. Dirt is an ingredient in soil, like flour is an ingredient in cake.

Soil is the cake, the end product of combining ingredients in a way that transforms them into something else entirely. To get cake, you mix ingredients and add heat and time. With soil, you mix ingredients and add life and time.

Soil is best understood as a process rather than a product. While there are plenty of products you can buy that call themselves soil, it would be better to think about them as ingredients for soil, but not the soil itself. Like cake baking in the oven, soil happens in the garden over time, under the nurturing care of the gardener.

To Till or Not To Till?

One emerging concept revolves around tilling and whether this is good for the soil or bad. The answer: it depends. There’s no avoiding tilling when starting a new bed. Soil must be tilled to incorporate organic matter into the native soil. Tilling breaks up hard ground to allow water to percolate and become soft enough for roots to have a chance.

Depending on your soil and how actively you garden, tilling may be a necessary chore until the microbial engine kicks into gear. This happens when you garden frequently enough that your soil is consistently moist 3 to 12 inches below the surface, and you’ve adopted a few easy gardening practices. At some point, you may be able to stop tilling entirely while actually helping your garden reach the next level of awesomeness. Are you ready to say goodbye to double-digging?

Think of the soil as an apartment building, with some residents living on upper floors where there’s more light, air, and heat. Others live on the bottom floors, where it’s cooler and darker. Given their druthers and food to consume, bacteria and fungus will settle onto the floor where they’re happy and thriving, while creatures such as worms act like elevators moving up and down between floors. All are consuming soil nutrients or each other — it’s a jungle, after all. In a nearly magical, symbiotic interface, these microbes hand off nutrients to plant roots. And here’s the cool thing: the roots also feed the microbes, a positive feedback loop that gets stronger over time.

If every so often the “apartment building” suffers a natural disaster that discombobulates everyone from their happy place, it takes a while for the structure to rebuild. All the ingredients are still there but in the wrong place. Getting back to their happy place takes time. If your garden’s soil is ready, maybe it’s time to try no-till gardening.

No-Till = Carbon Sequestration

Soil’s natural ability to sequester atmospheric carbon for generations is being considered a leading solution for climate change. The carbon being referred to are the microbes, fungus, worms, and many other living creatures in the soil, and the living and decomposing plant roots and compost they consume and support. Carbon is black (soot, coal), and as your soil incorporates more organic matter, it will darken towards black — visual evidence of carbon sequestration.

Supporting your garden soil’s life is a proactive statement that you are part of the climate-change solution. When you till, creatures die and fungal networks break. This begins the process of releasing sequestered carbon back to the atmosphere as carbon dioxide. In otherwise healthy beds, the microbes will rebuild over time, but wouldn’t it be more efficient if they didn’t need to?

Understanding Terms: Tilling • Forking • Cultivating

Tilling (or plowing) means breaking the soil’s surface with a shovel or other implement (disc, rototiller) and physically turning it over — what was below is above and vice-versa. As we stated earlier, there are times when this is necessary and the best thing you can do for your garden. We don’t want to cast any judgment about tilling, which has been with us since the dawn of agriculture.

Forking can be quite beneficial to a no-till bed. This involves pushing a four-pronged digging fork into the soil about 8-12 inches and wiggling it back and forth a few times — being careful not to turn the soil over. The best time to do this is after adding a layer of compost or amendment to the soil’s surface. The wiggling will work the compost down a bit (giving the worms a heads-up that there’s a feast up top) and open up the soil for better air and water penetration, factors that help your microbiome thrive. If plants are in the ground, be careful not to break the roots. Try your best to keep everyone in their happy place and you’ll be fine.

Cultivating means breaking up the surface (top 2–3 inches) of the soil using a hand cultivator or other implement. This is good for the soil and will not disturb the soil’s critters. Cultivating is good for weed abatement and helps break the soil’s surface, allowing for better air and water penetration.

When Clearing Beds, Leave the Roots

Plant roots are Nature’s perfect cultivators. Given the right conditions, a healthy plant will do a better job cultivating the soil than a plow can any day. Roots break up hard soil as they seek moisture, creating pathways for water to penetrate even deeper. After the plant dies, decomposing roots become food for the microbes, providing overall support for the below-ground ecosystem.

So rather than pulling roots out of the ground when clearing your garden, we recommend cutting the plant just below the root crown near the surface. This technique works for most annual vegetable and flower crops, some perennials, and even some weeds (weeds can be tremendous cultivators, as long as the growth node of the weed isn’t in the root). When you can, leave the roots and let them rot!

What Microbes Need

Microbes thrive in soil that is as moist as a wrung-out sponge up to about a foot deep, and loose enough to allow air to penetrate. These conditions are perfect for the good microbes, all of which are aerobic (needing air). If soil is too wet or watered only at the surface, anaerobic microbes can develop. These are usually smelly and indicate that things are not right.

Irrigation practices greatly influence how deeply water percolates into the soil. Roots penetrate only where the soil is moist. If you irrigate often but not for long (thinking this saves water), the water you apply stays at the surface, and roots never grow deeply. In extreme cases, the soil beneath the level where the water percolates can become hydrophobic and actually repel water.

On the other hand, if you irrigate for longer times but less often — and you’ve opened up your soil with a fork so that the water can penetrate — plant roots will grow deep. The more of a plant that grows below the surface, the more resilient it will be against above-ground conditions such as heat and drought. Deep roots act like radiators that keep the whole plant cooler.

Ancient Practices, Meet Modern Science

You’ve heard the joke — Q: what did they call organic gardening before 1950? A: Gardening.

For the inventors of agriculture and every farmer and gardener until about 100 years ago, organic was the only way to grow food, though it was not a term because it was the only method in use until the chemical/agricultural revolution of the 1930s. One outcome of the cultural revolution of the 1960s was reclaiming the word organic to define food grown without chemicals. Pushing back, big ag marginalized the practice, discounting it backward and calling those who practiced it wacky. It was only in the 1980s, after consumer demand for organic foods became a market factor, that university research into organic soil began.

Fortunately, many of those researchers were young and radical enough to be organic gardeners themselves. They put living soil under the microscope, where the abundance of soil life became apparent.

Permaculture, emerging from this marriage of organic gardening and soil science, has become a useful way of approaching soil as a process that can be nurtured and cultivated with profound results. Early permaculturists observed that barring a natural disaster such as an earthquake, flood, or landslide, Nature doesn’t turn over soil. This observation led to the first experiments in no-till gardening. Outcomes showed that undisturbed soil develops vast networks of mycelium that fuel decomposition so that communities of microbes — all attuned to the soil in that place — work together to provide optimal conditions for the plant.

As a gardener, you are a steward of your soil. Season upon season, we ask a lot from it. Because soil is a bit mysterious, it’s hard to know what to do. Time spent understanding and caring for your soil will be time saved solving problems above the ground. We hope these few tips will guide you in your garden for years to come!