Life in the Soil

James B. Nardi

Life in the SoilSoil is that dark stuff beneath our feet.  Or it is dirt. Or it is the digestive system of plants.  The more knowledgeable we become about the soil the more amazing it becomes.  We can understand cation and anion exchange, or how clay works to humidify a soil, or how to read a soil report and successfully amend  our soil but that tells us nothing about the teeming multi-trillions of denizens that dwell in our gardens and fields.

James Nardi starts with the bacteria and fungi in the soil, the nitrogen fixers, the digesters of plant and mineral matter and the largest populations in the soil. In a square meter of soil one could find 1010 bacteria, 109 protozoa, 5 million nematodes, 100K mites, 50K springtails, 10K rotifiers and tardigrades, 5K insects, myriapods, spiders and diplurans, 100 slugs and snails and one, just one vertebrate—possibly the farmer or the dog.

The bacteria and fungi live on plant roots, decaying matter and live in every small space in the soil. Nardi mentions a researcher in Britain who calculated that the surfaces lining all the tiny pores and passageways in a couple of tablespoons of soil add up to a quarter of a million square feet--the area occupied by a city block. But, we are warned, if there is no humus, no organic matter in the soil, if the clay particles are forced together then there is no room for these micro-organisms to flourish. 

As we climb the ladder of evolution Nardi leaves the microbes of the plant kingdom behind and considers the invertebrates, that 97% of the animal kingdom that have no backbone. They can be predator or prey, herbivores or fungivores, scavengers, shredders of plants, munchers of dung.  They are the nematodes, earthworms, rotifirs, mites, and others numerous. Possibly the earthworm is the most familiar of these creatures as they are so sociable, turning up in shovels of dirt, hanging out in the early morning to catch the first rays or drowning in the driveway after a heavy rain. Darwin devoted his last book to earthworms, noting that the worms can  examine a leaf to determine which end of the leaf will be easier to drag into its burrow. Earthworms are more effective than plows at moving earth, opening the soil to oxygen and water and providing habitat for smaller creatures. We are told to disturb the earth as little as possible but the earthworm never stops rearranging and reordering the soil for the benefit of all creatures, including us. There are many other soil movers and diggers, some that live on the surface of the soil, some that live in the layers of decaying plant matter that should be covering the soil and some that rummage through these layers from the top: all are looking for food, mates, reproduction chambers and to escape being someone else's meal.

The list of creatures that disturb the soil is very long, but think of beetles, ants, termites, wasps, hornets and bees, crayfish, moles and voles, chipmunks, woodchucks, snakes, birds, wombats (yes, their burrows can extend a hundred feet), mice and badgers (the best diggers), prairie dogs, meerkats and gophers.  Think of thousands of bison trucking their way across a prairie, digging it up with their hooves and leaving it open to sun and sky, or dung beetles dragging a fragrant ball into an earthen burrow with one precious larvae tucked inside each nutritious sphere.  When you remember that 30% of the production of a plant goes back into the soil to feed the life there (Arden Anderson, Science in Agriculture), then you have a picture of a fertile garden of Eden for creatures large and small but a garden in which the denizens are forever cultivating, pruning, tending and seldom relaxing.

The latter part of Nardi's book is a short course on how to get along with the creatures and plants of the soil. He talks about the many things we do that directly and adversely affect the soil and its inhabitants.  Acid rain for instance, caused by the pollutants from power plants and automobiles puts soils at risk, as does excess sodium, both explained in part three of the book.  James Nardi makes all of this easy to understand and relate to our soils. Naturally he cautions against using artificial fertilizers which deplete the soil.  He mentions that in 2005 it took three times the amount of artificial fertilizer to get the same results as gotten in 1975. The problem with these fertilizers is that they ultimately remove organic matter from the soil that gives the soil it's spongy, water holding capacity and turns large granules of soil into those small, packed together grains that have no spaces for water, oxygen or humus and, hence, no flora and fauna in the soil, all of this leading to erosion and dramatic loss of topsoil.

Another warning he gives is against invasive plants, one of which, garlic mustard, has no mycorrizal  association and a chemical given off by the roots disrupts such associations in its vicinity. And, to carry coals to New Castle, an invasive species of earthworm, when introduced to forests, decomposes leaf litter in a matter of weeks when the normal cycle would be several years thus depleting the nutrient load for other forest floor and soil dwellers.  

Composting is the answer to many of the ills we have visited upon the soil and its denizens. He advises cover cropping to restore organic matter and composting, complete with instructions, for smaller spaces. I might add, that disturbing the soil as little as possible beyond opening it to let in air and water is now thought to be the best way to handle the problem of disturbing soil life.

This book has pictures of many of these inhabitants of the soil,  many clear line drawings and some photographs that let us imagine our way into the soil as if we were visiting a new city. And this is exactly what this book is about. When we look over a field we might see some birds, a woodchuck or a rapidly disappearing rabbit but the sight of those few vertebrates, those surface dwellers we have seen all our lives, do not hint at what lives below.  If we think of that subsurface as city, filled with happy citizens going about their work of rotting, consuming, ionizing, reproducing, predating, and growing plants we will have the correct metaphor for the life beneath the surface. The first Europeans who came to this county had in mind that they were going to create a Godly place, The City on the Hill, they called it, that place where all was in accord with divine ideals.  How strange to find it beneath our feet and to understand, finally, that we must work in concord with these unseen creatures, as much a part of the Creation as we are and possibly more important.