feed the soil: my experiment with mycorrhizae

mycorrhizae illustration copyright Bio-OrganicsI 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.)

  1. devra says:

    i’m doing a lot of planting this spring and am eager to give this a trial. my concern is that i need to spray one of my beds with copper (some late blight last year), which would seem to destroy the fungi to begin with. any ideas?

    1. margaret says:

      I asked Graham and the founder of the company as well, and here’s what they say, Devra:

      “We would recommend not spraying the bed but to rely on the natural protection of the mycorrhizal fungi instead. The mycorrhizal fungi will protect her plant roots from harmful fungi (one of the many benefits of introducing “friendly” fungi) and that there should never again be a need to try to kill off soil organisms. It is also very difficult to completely kill all harmful organisms. If she must do it, she would then inoculate afterwards but she could also destroy other helpful organisms in the process of spraying.”

  2. Lillian Osborne says:

    So glad to find this conversation. There have been some articles about caring for the soil food web that have me wishing to know more about the soil microbes and their beneficial functions. The next step would seem to be to get my hands on Lowenthal’s book(s). I will be watching for any followup comments.

  3. Lillian Osborne says:

    Beth asked in an earlier post about striking a balance in till/no till soil care. Digging or tilling in the fall appears to do the most damage to the microbes and critters that have taken up residence in your soil during the growing season. The current thinking seems to be that shallow cultivation of your garden soil in preparation for spring planting is the most beneficial for the soil and the gardener alike.

    If your soil tends to become compacted, using a spading fork or broad fork to punch holes deeply into the soil works well to help get beneficial materials, air , and water to deeper levels This in turn encourages deeper rooting of your plants.

    We have a lot of clay in our garden soil, so when I prepare the beds I use a broad fork to punch holes , then rock back just a few inches before removing the tines from the soil. I do this at 6 to 8 inch intervals throughout the beds. Do not lift and turn the soil. As you add amendments some falls to the bottom of the holes, and as the season wears on, water and your microherd carries more goodies downward improving porosity and structure in the proess.

    1. Paul Caine says:

      This is just the advice I was after.
      I have a very reactive black clay soil and am looking for a way to improve the soil, without the “till” damage.
      What might you suggest for 5 acres of soil needing improving.?
      Thanks again.

      1. Ken mosley says:

        Get you some mycor plus from agusa or listen to Elaine Ingham microbiologist on utube u will get awesome soil results

  4. Marjie says:

    I have an abundance of the fungi in my garden. I know this because I was concerned when I thought I had veins of mold where I grew my veggies. I took a sample of it in to WSU extension office (Washington State University) and they said it was good fungi. I have a TON of it, and I noticed lots in my compost pile that sat during the winter. My question is….Can there be too much mycorrhizae in the soil? Can this be harmful to breath in while working in the soil?

    1. margaret says:

      Hi, Marje. I don’t know (and think it was smart to ask WSU — good for you), but here’s my non-scientist approach to answering:

      When I see too much of anything like that happening in the heap — a spot that’s too dry, too wet/slippery, anything that’s getting smelly, or fungi as you describe, I think it’s time to turn things and mix up the blend of ingredients. I believe that fungi are specific to particular materials (they develop on and break down one thing or another — not necessarily everything), so I have mostly had this happen when I got a load of wood chips, for instance, that were all one material…or a load of mulch that was too damp or I applied to thickly (or in a wet season). So I’d turn things to get air in there, add more “green” materials, and not worry.

  5. Chuck says:

    Thank you for the good info. I intend to try the m. fungi on my Dahlias this year to get better show blooms.
    Wondering why some plants are more mutualistic than others?

  6. scott says:

    I never heard an update on your experience? Are you still using Mycorrhizae? BTW, I loved you show today on weed ridding!

    1. margaret says:

      Thanks Scott re: the show. I’m not sure if there was any perceptible difference — but hmmm, hard to tell I bet, right? I guess I would have to do before/after soil analysis.

  7. Kristen Bishop says:

    Do you ever make it up to the Common Ground Fair? Two years ago I attended a talk about a no till method that is used in Korea. It was fascinating. The mycellium was captured in a box of white rice that was in the wooded part of the property. When one found the Mycellium it would then be used to inoculate a bed that had been solarized. A top layer of mulch would then be used to keep weeds down and feed that mycellium. The farmer giving the talk had stopped using tractors- which is startling when one is talking about acres of crops. He has a higher yiels and it costs less to produce. I bought the book Mycelium Running because I was told it describes how to do this & it will be how I tackle my acre plus plantings this year.

    1. margaret says:

      Hi, Marty. Yes, many versions can be applied that way. Normally each product gives instructions for dilution depending on application method, including that one.

  8. C&M says:

    We live on the edge of a river, where we have an long-established “swamp maple”. The tree is doing poorly. It seems to have responded positively to the rotted manure we spread beneath it mid-summer, but we are wondering if mycorrhizae can be part of the help this beautiful tree needs, and how/when to best get the fungi where it can help the tree.

  9. Tyler says:

    What are your thoughts on native vs nonnative mycorrhizae? Could the commercialization of mycorrhizae be introducing invasive fungi into our soils with unintended consequences? This sort of thing has happened before in the nursery world.

    1. margaret says:

      I don’t know, Tyler. I did that interview above 10 years ago, and haven’t since that first exploration used any products. Thanks for reminding me of a topic worth investigating.

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