By Paul James
That’s right. Soil is alive. It’s a living organism. And until you get your head around that concept, you’ll never really get gardening. Sorry, but it’s true. So make those three words your gardening mantra. Carve them into the handle of your favorite shovel. Paint them graffiti-style on your fence. Shout them out at the top of your lungs for all your neighbors to hear!
But just what do I mean when I say soil is alive? Well, consider the following.
More organisms occur in soil than in all other ecosystems combined. In fact, in just one tablespoon of soil there are more living things than there are people on the planet. (You might want to read that sentence again. It’s pretty mind blowing.) And in that one tablespoon lives a diverse and dynamic community composed of all sorts of critters, some of which you can see, most of which you can’t. But all play a vital role in keeping the soil healthy…and alive.
I want you to meet these critters, and learn to appreciate all they do for us, which is a lot. After all, without them, life as we know it would cease to exist. Seriously. They’re that important.
In one teaspoon of soil, there are as many as 100 million bacteria, most of which reside in the top six inches. These single-celled microorganisms reproduce by cellular division at an astounding rate. In fact, a single bacterium can produce 47 million descendants in 12 hours! Their population tends to remain fairly stable simply because they die at a rapid rate as well, and because many of the other critters you’re about to meet like to eat them.
Bacteria are responsible for such things as nitrogen fixation and sulfur oxidation, processes that make essential nutrients available to plant roots. They also aid in the decomposition of organic matter. Without them, plants simply cannot grow.
However, there are harmful bacteria as well, namely those that cause annoying and difficult to control plant diseases such as blight, leaf spot, and certain cankers. But hey, you’ve got to take the good with the bad.
Fungi are multicellular organisms that account for the greatest amount of living mass in soil. And within the world of fungi, there are the good, the bad, and the downright ugly.
Most gardeners, when they hear the term fungi, think of those that are harmful to plants, from powdery mildew on cucumbers to rust on roses to fusarium wilt on tomatoes. But there are all kinds of beneficial fungi as well. Many of them are saprophytic scavengers (they feed on all those dead bacteria), but their varied diet also includes leaf litter and other organic matter. There are also fungi such as mycorrhizae that enter into a symbiotic (mutually beneficial) relationship with the roots of plants to facilitate nutrient uptake.
So not all fungi are bad. In fact, some are quite good, especially mushrooms, morels, and truffles. Yummy!
Ever wonder what makes soil smell sweet? Or why the air smells so good after a spring rain? Well, it’s all due to Actinomycetes, a sort of cross between bacteria and fungi. These single-celled organisms devour the tough, woody stuff in the soil – chitin, lignin, and cellulose – as well as phospholipids (a fancy word for fats). In the process, they produce geosmin, the compound that gives the soil its distinctive, earthy smell. That smell is so enticing that geosmin is sometimes added to perfumes to give them an alluring earthiness. Eau de Compost, anyone?
Chances are you’ve seen Actinomycetes colonies in your own soil or mulch or compost pile. They look like grayish-white spider webs, and they’re a sign that your soil is healthy. So don’t freak out.
Actinomycetes also have antibacterial properties, which explains why Streptomycin and related antibiotics come directly from Actinomycetes.
Algae are bit players, really. They primarily live on rather than in the soil, because they contain chlorophyll and therefore need light to grow. Other critters dine on them.
These “animals” include amoeba and paramecium, both of which you probably observed under a microscope in science class. They reside in the top six inches of soil, where they graze on bacteria while other critters graze on them.
Again, most gardeners think of nematodes as bad guys, and some are. But soil is full of beneficial nematodes, and they comprise as much as 90 percent of the multicellular invertebrates in the soil. Millions can be found in a single shovel-full of good garden soil. Think of them as microscopic roundworms, chomping on fungi and recycling nutrients into the soil.
This group includes the more familiar forms of life – ants, beetles, crickets, earthworms, grubs, millipedes, mites, slugs, and so on. Collectively, you can think of these guys and gals (or in some cases, both) as nature’s rototillers, because as they move through the soil in search of food, they aerate it. They also leave behind their nutrient-rich poop.
But just what do they – and all their fellow soil mates – actually eat, besides each other? Organic matter in its myriad forms, that’s what. And that’s why the only way to keep soil alive is by adding lots of organic matter – shredded leaves, grass clippings, homemade compost, barnyard manures, or bagged products from Fox Farm, Back to Nature, and other companies committed to keeping soil healthy…and alive.