Guest Post: Want Happy Plants? Feed the Microbes!

Five Ways To Improve The Health And Diversity Of Your Soil Food Web: A guest post by Phil Nauta, The Smiling Gardener.

Most of the work in our gardens is done by the “soil food web.”

If you’re not familiar with this term, it refers to the inhabitants of the soil, including plants and animals, and importantly (the very, very tiny) microorganisms. They do the work, and us gardeners are really just helpers.

All of these soil dwellers manipulate the soil so it can support life. They also feed and protect plants. In fact, microorganisms play many vital roles, and there can be a billion of them in a gram of healthy soil.

Unfortunately, most of us don’t have healthy soil, especially when we’re starting out, and without them, our garden gravitates toward being a desert, which is happening on much of our agricultural land. In fact, in most places where humans have spent some time, the health of the soil has gone downhill, but fortunately, we can move our garden back toward a lush paradise.

A lot can be said about exactly what these organisms do for us, but I want to jump right into how to make sure they’re in our soil. While it’s less than ideal to bring in external inputs when we’re trying to be as sustainable as possible, our gardens often just need a little help at the beginning to move back toward a state of microbial abundance.

Here, therefore, are five ways to improve the health and diversity of your soil food web.

1. Compost. I know you already know about this one, but I have to list it first because it’s arguably the most important. We know compost brings in crucial organic matter to our soil as well as a broad array of nutrients, but just as important are the microorganisms. It needs to be well-made, aerobic compost in order to bring in aerobic microbes, which tend to be the most beneficial. You can make it yourself outside in a big pile, or even inside with earthworms. In the meantime, you can get it from the garden center.

Action Step: Apply one-fourth to one-half inch of quality compost to your gardens this spring and/or fall. Doesn’t sound like much, but it’s actually more than enough.

2. Compost tea. Compost tea has been made for centuries by putting some compost or manure into a pail of water for a few days, stirring occasionally, and applying it to the soil and plants as a fertilizer. Nowadays, we often add some microbe foods to feed the microorganisms, and aerate the water to give them oxygen and physically pull them from the compost. If done properly, this yields a vast number of diverse, beneficial, aerobic microbes that can be applied to the soil much less expensively/faster than compost, and can also be applied to the leaves which need to have these microbes, too. Making good compost tea requires some knowledge, so be sure to research before getting into it.

Action Step: If you’re interested in this topic, read ‘Teaming With Microbes’ (note from Gen: this book changed my gardening life!), ‘Compost Tea Making’ and the more detailed ‘Compost Tea Brewing Manual’ before getting started.

3. Leaf mold. Every year, I watch gardeners rake their leaves to the curb for the city to take them away. Then some of them buy it back in the spring as “leaf mold,” which is just leaves that have been piled up and partially broken down largely by fermenting microbes, which is why it smells kind of like a brewery. In most climates, the leaves would have been better left right in the gardens over the winter (sometimes people in wetter climates don’t want too many leaves piled up because it can promote slugs and other pests). But if you have extra leaves, you can rake them into a pile to make your own leaf mold, which can be applied in the spring as a terrific mulch that’s loaded with beneficial fermenting microbes.

Action Step: This fall, keep most of your leaves in your gardens or mow them right onto the lawn. If you have extra, compost them or make leaf mold.

4. Effective Microorganisms (EM). It’s not as well known in North America as in Asia and many other countries, but EM has been used successfully since the early 80s to inoculate plants, compost and soil with beneficial fermenting microbes, including some of the organisms in leaf mold. Whereas with compost tea we try to get tens of thousands of different species of microbes, EM contains only 5-20 specific microbes (plus perhaps a couple hundred wild ones) that just happen to be incredibly important in the garden. You can’t find it in most garden centers, but you can buy it online as ‘effective microorganisms’ or ‘efficient microbes’ for $15-$30. Sometimes the results are quite amazing. It’s easier to use EM than compost tea.

Action Step: Get some EM and apply it this year – to your soil, compost and especially plant leaves – with a watering can or sprayer. It’s best used regularly, such as monthly.

5. Mycorrhizal fungi. These special fungi form relationships with the roots of over 95% of plants. They bring water and nutrients to plants in exchange for food from the plants. This symbiotic relationship is vital for optimal plant health. They should already be in our gardens, but as with many important organisms, they often aren’t. You can buy them as a granule or powder that is best applied at planting/seeding time when you can actually get it down into the soil near the roots, since this is where the relationship occurs. The powder can also be watered into porous soils. A good product will have several different species of fungi. Some garden centers carry it, but again, you can buy it online.

Action Step: Get some mycorrhizal fungi and apply it whenever you plant and seed this year. As long as you keep the fungi happy (proper watering, no chemicals, no tilling), you don’t have to apply it again.

I’m very much into creating self-sufficient gardens that don’t require external inputs in the long run, but if you live in an area that has seen much human activity, it’s often necessary to bring the soil back to more of a balanced state, not only nutritionally, but also in terms of the actual inhabitants of the soil.

As our gardens age, if we’ve focused on creating a proper ecosystem, they will largely take care of themselves. But in the beginning, these five methods are exceptionally helpful to achieve balance more quickly.

Phil Nauta is a SOUL Certified Organic Land Care Professional and author of the book ‘Building Soils Naturally’, to be released by Acres U.S.A. this spring. He has taught for Gaia College and been a director for The Society For Organic Urban Land Care. He had been an organic landscaper and ran an organic fertilizer business before starting his organic gardening site to teach others what he has learned.


  1. Kate says

    Great list of ways to introduce microbes into the garden, Phil! I especially like that you included action steps – not just what to do, but how to get started!

    I’m a huge fan of worm composting, so I had to smile at suggestion # 1 when you mentioned composting with worms. I have a Worm Factory 360 (from Nature’s Footprint) in a closet in my laundry room at home and I get really high-quality compost out of it. Worms work with billions of aerobic bacteria in the Worm Factory and the stuff that comes out is teeming with life for my garden.

    • says

      Kate, I couldn’t agree more! I just adore my Worm Factory and it’s nice that it takes up so little room, yet is so effective at breaking down kitchen scraps. They’re definitely easier pets than a cat!

    • says

      Thanks, Stevie! Yeah, Phil definitely knows his stuff. One thing I keep thinking – wildlife gardening is kind of “in” right now. But we forget about the wildlife in our own soil – the microbes! Yet they are every bit as important as the more visible bugs and animals.

  2. says

    I love learning about new ways to grow soil and EM is totally new to me. I don’t use a lot of compost teas but I do swear by leaf mold. It gets mixed into the soil mix I use to fill almost every planting hole I dig. The action steps after each recommendation certainly make it easy to know where to begin to start feeding your soil.

    • says

      That’s awesome, Debbie. EM was totally new to me, too. Love that after so many years of being in this business we can still learn new things every day. This is probably the element I like best about gardening.

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