Gardening

Dirt on Dirt

Even as gardeners, it’s not something we think about all that much. But if it weren’t for soil, we wouldn’t be here. We’d be on Mars. Or worse.

A mixture of air, water, minerals and countless microorganisms, dirt, or, more precisely, soil, is the thin outermost layer of the Earth’s surface. But as with our own skin, we can’t live without it: everything we eat comes from soil, either directly or indirectly, which also affects the air we breathe, absorbing carbon dioxide, dust and gasses.

And all the time, soil is changing, evolving and teeming with life. In fact, there’s more life in the dirt (billions of organisms per teaspoon) than on top of it. The original recycler, soil takes on whatever falls onto it, and then those microorganisms get to work, breaking it down and taking possession. One publication refers to healthy soil as “a frenzy of reproduction, ingestion and death.” And from that comes life.

As vast and varied as the planet itself, soil forms from surface deposits of rock, sediment, sand, silt and clay. It’s a lifelong process, with external factors such as sunlight, water, wind, ice and time working together—and sometimes at odds—with one another. A tree falls down and decays, then microscopic critters get busy, and eventually all that organic matter is reabsorbed by the soil, providing nutrients for the next generation of life. Soil formation is, in fact, so slow that it is considered by many circles to be a nonrenewable resource.

“I learned many years ago that over 90 [percent] of my success in the garden hinged on one thing: the quality of the soil that I plant in,” writes Mark Cullen, our own Gardening Editor, on his blog. “It goes without saying that my golden rule for a productive garden is, by extension, at the root of our success as a civilization. Perhaps it does not go without saying; after all…most of us are wholly unaware of the importance of soil.”

That lack of awareness is one factor among many that threaten the human food supply. Historically, cities have appeared in fertile areas (consider everything from ancient Mesopotamia to modern-day Toronto). As those fledgling cities grew, new homes and businesses pushed out the farmers and gardeners. Food producers migrated onto land that was increasingly marginal, while prime agricultural land was lost forever. Arable land still being gobbled up at a rate of nearly two hectares (five acres) every minute.

Soil also plays an important role in climate change. As one of the largest sources of carbon on the planet (second only to our oceans), tilled soil releases sequestered carbon into the atmosphere. As a consumer of dead leaves and plant life, soil gathers carbon and then slowly releases it in the form of carbon dioxide. Soil can also produce other greenhouse gasses such as methane and nitrous oxide. As the planet warms, those processes speed up.

There are a number of potential unknowns in the climate change situation. Higher temperatures and increased carbon dioxide could lead to increased plant growth, leading to increased decaying plant matter in the soil, which, in turn, would be affected by increased activity by the soil’s microorganisms. If any of those factors fail to keep pace with the other parts of the soil life cycle, things could take a turn for the worse.

“The exact direction and magnitude of those impacts will be dependent on the amount of change in atmospheric gases, temperature, and precipitation amounts and patterns,” says a 2012 study published in Soil Horizons. “Recent studies give reason to believe at least some soils may become net sources of atmospheric carbon as temperatures rise and that this is particularly true of high latitude regions with currently permanently frozen soils. Soil erosion by both wind and water is also likely to increase. However, there are still many things we need to know more about.”

Indeed, it’s a topic we all should know more about. As activist Peter Maurin said, “It is impossible to have a healthy and sound society without a proper respect for the soil.”