Turns out, it was the garlic. We’d pressed hundreds of cloves into pots in the fall, where they sprouted while awaiting the completion of our newest garden beds. But by now, they had far outgrown their nursery; yellowing tips and roots poking through the drainage holes in the bottoms of their pots spoke to me of stress, frustration. They seemed to suffer from their extended isolation, yearning, as living beings do, for the depth and diversity of context.
I was surprised by the flood of joy and relief I felt when we finally transplanted them into the garden. Lifting each plant from its plastic container, we gently massaged the tangled, spiraling root mass, encouraging it to grow freely in the soil.
In it’s early days, a plant directs most of its attention downward, using energy stored in the seed to develop a root system, until leaves emerge and begin their alchemic conversation with light and air. Roots, like our skin, act as organs of perception, the interface between an organism’s internal and external worlds. As young root tips grow, and from them smaller rootlets and exquisitely fine root hairs, they sense their way into the soil, seeking moisture and nutrients, excitedly exploring in multiple directions at once. From their sensitivity and dynamic responsiveness, the root system takes its own unique shape, particular to the individual plant in its particular context.
As they establish their own home in the soil, they secrete sugars, fats, and proteins, a “gelatinous sheath of food around the root” which “creates a buzz of biological activity, particularly near the root hairs.” (David George Haskell, The Forest Unseen, 2012, p. 225) Roots do not make their soil journey alone. In a healthy soil, the rhizosphere is a hotspot of life, pulsing with animal-vegetable-mineral interactions.
Bacteria, the common ancestors of all of earthly beings, are dazzlingly diverse, creative, and complex participants in soil ecology. In one gram of soil live an estimated 1 million different bacterial species. Of these, only a fraction of a percent can be observed in the lab. “The interdependencies among the other ninety-nine percent are so tight, and our ignorance about how to mimic or replicate these bonds is so deep, that the microbes die if isolated from the whole. The soil’s microbial community is therefore a grand mystery, with most of its inhabitants living unnamed and unknown to humanity.” (Haskell, p.223)
We may not have named or studied the vast majority of living bacteria, but we have at least a sense of their significance for soil ecology. Bacteria play the extraordinary role of cycling all kinds of organic and inorganic material throughout earth systems. They transform energy, making life possible for all kinds of other creatures in the soil food web. As biologist James B. Nardi writes, “It is to the bacteria of the soil, with a little help from the larger inhabitants of the soil, that most of the credit for the constant renewal of our earth is due.” (James B. Nardi, Life in the Soil, 2007, p. 51)
Plant roots attract these metabolic magicians by releasing substances which bacteria can utilize as a source of energy. With the help of enzymes, soil-dwelling bacteria facilitate decomposition, turning nutrients into a form that plants can use. In doing so, bacteria become a “living reservoir” of fertility; they take up nutrients and store them in their bodies, thereby bringing those nutrients into the soil food web and preventing nutrients being flushed away by rain.
Some bacteria thrive in anaerobic conditions (like that vast majority of bacteria in our gut, for example), while others require oxygen in order to survive and reproduce. In composts, it is often easy to detect the presence of anaerobic bacteria through your nose: the sharp, putrid smell of ammonia is a symptom of anaerobic decomposition. Anaerobic composts can foster pathogens and drive out beneficial aerobic bacteria. The smell of ammonia also indicates that nitrogen is being given back to the atmosphere as a gas rather than becoming loosely bound up with humus in the decomposition process. In soils, another sign of anaerobic conditions is color. In a well-aerated soil, particles have an iron-oxide coating formed in the slow process of mineral-weathering; this gives the soil a reddish- or yellow-ish brown hue. In the absence of oxygen, this coating is stripped away, and the soil will look a dull, mottled gray.
That clean, earthy smell that gardeners know so well as a sign of “good soil”? Your nose has not deceived you. Celebrity among soil microorganisms are aerobic actinomycetes, who produce enzymes containing volatile oils that give soil the odor we find so pleasing. Actinomycetes have characteristics of both bacteria and fungi. Their special talents include the break-down of lignin and other difficult-to-digest compounds in woody material; formation thread-like filaments that grow into a network similar to fungal mycelium; and production of antibiotics. They can also take up residence in tiny nodules on the roots of certain plants, sharing in some of the plant’s sugars, meanwhile transforming atmospheric nitrogen into a form accessible to the plant.
Bacteria travel by propelling themselves along tiny water channels using a whip-like structure on their bodies called flagella, use more passive means by hitching a ride on water, roots, soil critters, or other material, or by squirting bacterial slime (“biofilm”) to give themselves some momentum. This slime, slightly alkaline, “not only influences the soil pH where it counts most, in the rhizosphere, but also buffers the soil in that area, so the pH remains relatively constant.” (Lowenfels and Lewis, Teaming with Microbes, 2010, p. 49) The biofilm’s sticky quality also affects soil structure by binding soil particles together to form aggregates. One of the simplest ways of getting a sense of a soil’s structure is by taking a handful of soil, squeezing it into a ball, and then opening your hand and observing the degree to which it crumbles or holds together. Good garden soil — thanks in part to bacteria and their biofilm — is somewhere between compacted clay and loose sand, a “just right” loam that has enough stickiness and moisture to form varied clumps, while allowing for drainage and air infiltration.
One of bacteria’s primary partners in decomposition are fungi, which weave beautiful “subterranean spiderweb” structures among decaying organic matter (Haskell, p. 226). Like bacteria, fungi help facilitate the recycling of nutrients, but with their own distinct habitat preferences and metabolic styles. Some fungi are much-appreciated for their propensity toward mutualistic associations with plant roots. These myccorhizal fungi connect with plant roots, either externally (ectomyccorhizal) or internally (endomyccorhizal), gaining access to carbohydrates produces by their host’s photosynthetic activity. In return, the myccorhizal threads grow out into the soil, becoming an extension of the plant’s root system. Their hyphae are many times finer than even the finest root hairs, with a much higher surface area and thus higher capacity for water and nutrient absorption. The fungi receive quite a large share — an estimated 20-40% — of the plant’s total carbon intake, which hints, perhaps, at the significant benefits of this association for the plant.
Protoctists are single-celled eukaryotes who are thought to be the primary predators of soil bacteria. They live in films of water on soil particles, and have also developed associations with various animals by taking up residence in the microbially-rich environment of the digestive tract. Looking at one through a microscope, I caught a glimpse of it’s cilia, extremely fine hairs protruding from its body which wave about rapidly, drawing bacteria, algae and water into itself. In the same sample, a comparatively long, slender nematode wriggled quickly by. Nematodes also feed on bacteria, as well as protozoa and fungi. Some fungi can detect the presence of nematodes, send out odors to lure them closer, and then creatively trap them by producing a sticky substance or even a snare-like loop.
Arthropods we can often see with the naked eye. Their identifying features are exoskeletons and jointed legs; they are a diverse bunch, including little critters like spiders, ants, mites, sowbugs, beetles, springtails, and more. Some are predatory, others are detritivorous, meaning that as they eat they break down material into finer pieces which smaller organisms can then begin munching on.
And, of course, there’s the humble and heroic earthworm. Aristotle deemed them the “Intestines of the Earth”. According to Charles Darwin, who observed his garden worms closely over the course of his life, “The plough is one of the most ancient and most valuable of man’s inventions; but long before he existed the land was in fact regularly ploughed by earthworms. It may be doubted whether there are many other animals which have played so important a part in the history of the world as have these lowly, organised creatures.” (1881) I’ve always been told that worms were a good sign in the garden, and delighted in watching them slide across the ground, bend their bodies this way and that, encounter different shapes and textures, and slip back into the safe, dark earth. But in what way do these ‘lowly, organised creatures’ plough? And how does this influence life in the soil?
As a wildlife tracker, I’ve spent a good many hours kneeling close to the ground to look, smell, and poke one of the most revealing signs about an animal’s life — it’s poop. Worm poop, or worm castings, are a good place to start. A worm’s digestive tract, like ours, is an incubator for bacteria; detritus and soil particles that pass through it are microbially richer coming out the other end. Castings also tend to be higher in calcium, nitrogen, phosphorous, and potassium, and less acidic, than the surrounding soil — conditions worms themselves prefer as habitat. They are not passive occupants of their environment; rather, their presence actually changes qualities in their environment to be better suited to their needs. Our gardening and theirs are intertwined.
Their burrows are constructed, as Darwin described in rigorous detail, by a combination of maneuvering and munching their way through the soil. They have a habit of drawing leaves down into their burrows to plug them, or to eat later, underground. Bringing leaves and other detritus downward, they integrate decomposing organic matter into the topsoil and below, essentially cultivating the soil like we do, but gently, with more finesse, and collective power.
There is what seems to me a beautiful partnership between the burrowing actions of worms and the growth patterns of plant roots. Burrows create space in the soil, aerating it and allowing for drainage, which is conducive to the bacteria and other creatures who have associations with plant roots. Also, the burrows themselves become lined with castings. It is as if those searching roots are invited in to a perfect little tunnel, pre-drilled by the muscle of the worms, and lined with nutrient-rich, biologically active soil. As the roots grow, they continue to break up compacted ground, opening up new territory for the worms, and as the worms burrow, they too loosen the earth, making room for further root explorations.
“At present I am preoccupied with sense-impressions to which no book or picture can do justice. The truth is that, in putting my powers of observation to the test, I have found a new interest in life. How far will my scientific and general knowledge take me: Can I learn to look at things with clear, fresh eyes? How much can I take in at a single glance? Can the grooves of old mental habits be effaced? This is what I am trying to discover.” (Italian Journey, September 11, 1786; p. 21 in Auden translation/edition 1982)
What I have described here just barely skims the surface of what we "know" about soil ecology. And all that we “know” about soil ecology just barely skims the surface of the living realities beneath our feet, which are largely beyond human perception and narratives. However, those worlds are not completely inaccessible to us, either. Plants and their partners in the rhizosphere are continuously expressing themselves in form and behavior, and through themselves expressing their contextual relationships.
Their expressions are the shared, experiential language of the “biospheric web” in which our own senses and sciences are embedded. “It is no more true” cultural ecologist David Abram writes “that we speak than that the things, and the animate world itself, speak within us[.]” (Spell of the Sensuous, 1996, p. 85) As human animals, we have access to this language through our senses, our body, our felt experience. The smell of earth, the glimpse of a fine fungal web tucked beneath the leaf litter, the sound of water finding the air pockets in soil, the texture of worm-tilled earth, the feeling evoked by pot-bound garlic… all speak to us, invite us into conversation.
Amy Stewart. 2004. The Earth Moved: On the Remarkable Achievements of Earthworms.
David Abram. 1996. The Spell of the Sensuous.
Stephan Harding. 2006. Animate Earth
George David Haskell. 2012. The Forest Unseen: A Year’s Watch in Nature
Jeff Lowenfels and Wayne Lewis. 2013. Teaming with Microbes: The Organic Gardener’s Guide to the Soil Food Web
Charles Darwin. 1881. The Formation of Vegetable Mould Through the Action of Worms With Observations on their Habits
James B. Nardi. 2007. Life in the Soil: A Guide for Naturalists and Gardeners
Craig Holdrege. 2013. Thinking Like a Plant
And learning in the garden at Schumacher College with Jane Pickard, Jane Gleeson, and the Sustainable Horticulture apprenticeship team