feed the soil: my experiment with mycorrhizae
I ALWAYS SAY “feed the soil, not the plants,” which for decades has meant to me to turn in compost—lots and lots of compost, and then more—and every few years a topdressing of organic fertilizer. Lately I’ve been curious what more I can do, as stressors ranging from dryspells to disease test me and the plants. I’d often read about inoculating the soil with mycorrhizae–myco means fungus and the suffix means root, so literally root fungi, a word used to indicate a symbiotic relationship between the two. Until last fall, at garlic-planting time, when I purchased $49.50 worth (enough for the garlic, plus my whole vegetable garden) I’d never experimented hands-on. More about my mycorrhizae adventure:
The tipping point had been meeting Graham and Layla Phillips, who had recently taken over Bio-Organics, founded in 1996 and one of the first companies to commercialize mycorrhizal agricultural products (disclosure: they have advertised on A Way to Garden). We got to talking, and I pestered them with my usual endless questions–and then bought myself that jar of a blend of viable beneficial organisms from their online store.
I didn’t just take their word for how it all worked, however; I dug deeper. Extensive Texas A&M research over more than 25 years reports that the benefits of mycorrhizae include plants that are more vigorous, with increased drought and disease resistance and the ability take up more nutrients and water. They may also need less pesticides because of their overall better response to stress. (Mycorrhizae have even been used by Aggie researchers on Texas lignite coal-industry land to try to revitalize it after mining, but I’m hoping your garden isn’t in that condition!)
Even deeper background: Mycorrhizae weren’t “invented,” not by Bio-Organics or Texas A&M any other current commercial producer or research institution. They’re a group of naturally occurring soil organisms, one or more species of which most plants depend on to thrive (different plants, different preferred species). The interaction is mutualistic, not just one-way: The fungi use the Carbon produced by the plants to support their own functions, in turn helping the plant to reach farther into the soil by creating an extensive network or web of fungal filaments–they look like root hairs–called hyphae.
When I first read about using mycorrhizae, it all sounded a little like pre-treating beans and peas with Nitrogen-fixing inoculant, or taking probiotics for a healthy gut—you know, natural, or holistic. But of course those examples are uses of friendly bacteria, not fungi like the mycorrhizae. (And you know how I’m fascinated by the power of fungi.)
Much of the commerce in mycorrhizae to date has been geared to agriculture and the nursery industry. Grapes, for instance, are very dependent on mycorrhizae (as are roses, for another example), so vineyards are one industry that extolls their virtues. Spurred by Texas A&M findings, wholesale nurseries, including giants like Monrovia, have begun inoculating their potting soils, seeking potential benefits such as reduced transplant issues and faster establishment.
Such industries hadn’t initially come to mycorrhizae seeking a ”save the earth” solution, says Graham (read more about the Wharton law-and-business graduate in this “Philadelphia Inquirer” story), but rather a better economic equation in crop production. For instance, they may harvest at a younger age (as with the grapes), or reduce fertilizer costs, or otherwise improve the bottom line.
Now other potential customers—including more gardeners—are coming asking about natural solutions to growing success.
Like me with my curiosity about fine-tuning my soil-feeding mantra. And so when the raised beds here can be worked in a couple of weeks, I’ll continue my experiment with mycorrhizae, by using the rest of my supply.
I’d love to hear if you’ve begun your own experiments with these fascinating microbes and what your experience has been.
mycorrhizae 101, the basics
I ASKED GRAHAM PHILLIPS a few key practical questions about using mycorrhizae, in this short Q&A:
Q. When do I apply mycorrhizae? Do I re-apply every year?
A. Mycorrhizal products are often used by gardeners when sowing seeds, when transplanting, or to inoculate a bed before planting, working them into the top 4-6 inches. Inoculated soils will actually improve year after year, so it’s a sustainable product.
Q. Do I till in coming seasons?
A. We recommend no- or low-till practices, so the network of filaments, or hyphae, can develop and flourish year to year. Keep using your compost.
Q. Do I use fertilizer as well?
A. Many synthetic plant foods, especially fast-acting liquids, harm microbial activity in the soil and create fertilizer-dependent plants, so we don’t recommend using them. We say that the fungi are not an “add-on-” to a chemical-fertilizer routine, but best used “instead of.” We recommend ongoing use of compost, compost tea, cover crops, and if needed, small amounts of dry organic fertilizers that release slowly.
Q. Does mycorrhizae work on all plants?
A. There are a few plants that are said to be non-mycorrhizal, meaning they don’t form the mutualistic relationship with the microbes. These include blueberries and other ericaceous plants such as azaleas; brassicas (cabbage, broccoli, mustard, etc.); spinach and beets.
Q. Where do I store leftover product, or can I?
A. You can store it for two years, preferably in a cool, dry place, but it will last longer. After two years the spores begin to degrade as time passes, but many will remain viable–you would just have to use a little more each subsequent year.
(Top illustration courtesy of Bio-Organics.)