June 4, 2012

3 Microbial Inoculants To Improve The Health Of Your Soil Food Web

Microorganisms are vital to the health of our gardens. They:

  • Provide nutrients for our plants
  • Protect our plants from predators
  • Drastically improve soil health
  • Clean and filter our water
They keep insects and diseases at bay - and even help control weeds - simply by being there and performing all of the above tasks. In fact, that's one of the main reasons we use compost, to increase the number - and diversity - of microorganisms in our soil food web.

They were probably present in our garden soil in abundance 100 years ago, but for many reasons, they're often lacking these days.

The problem is, good compost isn't cheap, and it takes time and materials to make it yourself. That's not to say you shouldn't use compost, but I'm sure we can all agree that we never have as much as we'd like.

That's where microbial inoculants come in. They're inexpensive, quick and easy to use, and we can apply some of them not only to the soil, but directly onto the leaves.

There are new kinds being developed all the time, but there are 3 proven ones I've used regularly since moving to organic gardening in 2005:

1. Compost Tea

The simple compost tea recipe I use every time is to put a few cups of quality compost into a pail of water and bubble air through it with an air pump. This air helps pull the microorganisms from the compost and allows them to breathe. We generally want to encourage the aerobes, the microorganisms that breathe air.

We also add foods like kelp and molasses to feed the microorganisms. Doing this means we actually multiply an incredible number of beneficial microorganisms, ending up with as many as 100 trillion per millimeter of liquid. This is then sprayed directly onto the soil and plants, where 5 gallons of good tea can do more than an acre.

2. Effective Microorganisms

EM is a liquid of "facultative anaerobic" microbes. They're a bit of a different set of microorganisms than the ones we get from the compost tea, but they still provide amazing benefits for your garden when combined together in the specific proportions of effective microorganisms.

They can live in air, but also in low oxygen conditions. With compost and compost tea, we want aerobic microorganisms, but with EM, we're okay with the fact that they're different. They’re also called fermenting microbes and some of them are the same ones that make your bread, beer, wine and yogurt. This is used similarly to compost tea, but it is diluted often with 100-1000 parts water first - a little goes a long way.

3. Mycorrhizal Fungi

I use mycorrhizal inoculant nearly every time I plant. Over 95% of plant species join up with mycorrhizal fungi at the root level. The fungi provide nutrients and water in exchange for carbohydrates and other treats from the plants.

In fact, many plants will trade more than 50% of their carbohydrates with these fungi and other microbes. Mycorrhizal fungi improve the soil and are among the most important microorganisms that form relationships with plants. Unlike the other 2 inoculants, this is applied only to the soil, and it's best if you can get it on the roots, which is why I try to apply it during planting.

I’ve had great success with these 3 inoculants in my own gardens and my clients' gardens. I've seen much healthier plants, increased yields and better-tasting food. I’ve controlled diseases such as mildew and insects such as spider mites.

Feel free to ask me any questions below.

About the Author

Phil Nauta is a SOUL Certified Organic Land Care Professional. He's the 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 was an organic landscaper and ran an organic fertilizer business before starting Smiling Gardener to teach practical organic gardening tips.


Phil Goold is a retired landscaper of 30 years. He loves being outside more than anything else, except maybe pie. He enjoys connecting with other landscapers and gardeners because everyone brings something new and fun to the table. Connect with Phil on Twitter and Google+.

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