Fungi at work

Although we can’t see it, we live in a microbial soup. I just learned that there may be a Milky Way of viruses that floats on air currents around the globe and that trillions fall to earth every day. We know our guts are inhabited by billions of bacteria that we can’t get along without. A teaspoonful of soil contains up to a billion bacteria.

    Some of the most important players in this microscopic world are fungi. This summer has produced a particularly handsome crop of mushrooms and other fungal growths in woods and shady gardens in my area.  Walking woodland paths this month, I can’t resist stopping to snap photos of new, colorful fungal growths that seem to pop up almost every day.

Wet, rotting wood displaying a fungal bonanza

    The mushrooms I’m admiring are just the tip of an underground iceberg, the fruiting bodies of vast networks of thread-like fungal hyphae in the soil below. Compost couldn’t happen without the work of soil fungi. Bacteria, fungi, nematodes, insects and protozoa all work together to break down the organic material we throw on the compost pile into nice black compost.

Microscopic view of fungal cells

    I was amazed to learn a few years ago that experts can customize the balance of fungal and bacterial content in compost by choosing the right mix of ingredients. This is when they make compost on the scale of tons, moving giant mounds of material around with backhoes. 

At large-scale composting operations, piles are turned by machines

High-carbon, tough woody materials are what soil fungi like, so our yard’s endless supply of oak leaves predisposes the compost I make to have high fungal activity. I once had my compost tested for its biological content. The report came back showing excellent fungal presence.

    That’s just as well, because shrubs, trees and perennials—what my garden is mostly made up of—particularly like soil and compost with lots of fungi. By mulching with fall leaves and wood chips, I give the fungi even more to chew on.

Shredded leaf mulch

    Not only are these organisms hard at work in the soil. They actually create an underground architecture in the rhizosphere, the top few inches of soil where there’s the most oxygen and the most biological activity takes place. Roots and soil fungi have evolved to work together, exchanging nutrients. 

A stump in my yard is hosting this impressive mushroom bouquet

     This justifies the lazy woman’s approach to soil amendment: layering compost and good stuff such as composted manure on top of the soil and letting the soil organisms do the work of mixing them in. Tilling the soil, or even turning it with a spade, breaks up those underground networks that fungi have labored to create. That makes it harder, not easier, for plants’ roots to obtain the nutrients they need.

Let soil organisms do the digging

    As the beans and tomatoes in the vegetable garden finish producing and start to wind down, it’s almost time for me to play my part, spreading some compost on top of the bed. By spring, those fungi will have made the soil ready for another season’s planting. I appreciate their beautiful above-ground creations, and I’m even more grateful for the work they’re doing underground.