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Teaming with Microbes – A Close Look, Part 2

Teaming with Microbes, A Gardeners Guide to the Soil Food Web was reviewed in an earlier post Teaming with Microbes – In-depth Book Review and in Teaming with Microbes – A Close Look, part 1.  In this post I’ll look at more content of the book and discuss their validity and the validity of the soil food web. A gardener can learn a lot by looking at these topics in some detail.

Teaming with Microbes - A Close Look, Part 1

Teaming with Microbes – A Close Look, Part 1

Teaming with Microbes – A Close Look

Items in quotes are taken from the book. In some cases the quotes have been shortened to make the concepts easier to understand but as much as possible I have used the same wording as found in the book.

Compost Tea Adds Diversity

“You can’t add too much compost tea. It does not burn plant roots, or leaves. Repeatedly adding compost tea only increases diversity of the microbe population. “

The reason you can add as much compost tea as you want is that it is not adding very much to the soil. It clearly has very few nutrients since an excess will not burn roots and leaves.

If you make a big batch of compost tea and add it repeatedly – how can this add diversity? Each addition would add the same microbes. The only way to increase diversity would be to start a new batch using a different source of compost and/or a different brewing method which might grow different microbes. Repeated applications of tea made , the same way, with your compost will not increase diversity.

One of the key claimed benefits of compost tea is to add diversity. The problem is that the gardener does not know which species are in the soil or which species are missing from the soil. They don’t know which species are in tea. And once applied, they don’t know if diversity has changed.

Do you really need more diversity? Maybe what you have is working just fine?

Current scientific testing of compost tea, applied in field situations has not shown any consistent benefits.

Moss and Fungally Dominated Soil

“Moss in lawns indicates that the soil is fungally dominated and acidic. Making the soil more bacterial will get rid of the moss. To do this, add bacterial teas. ”

Moss does not indicate acidic soil conditions – it grows just fine in alkaline soil. This is a well known myth.

Acidic soil makes more nutrient ions available to plants which makes them grow better. But … moss usually indicates a soil that is poor in nutrients – which is more likely in alkaline soil.

In home landscapes most lawns are growing over tree roots; the trees want a fungal soil according to the food soil web. Adding bacterial teas, if they worked, would keep down the moss and help the grass grow, but harm the trees. This is a good example of how the soil food web rules do not help a gardener who now needs to choose between trees or grass.

The reality is that the soil already has both bacteria and fungi. You do not need to add either. Moss tends to grow in low fertility lawns – usually due to a lack of nitrogen. Increasing the nitrogen levels will make the grass grow better and reduce the amount of moss. For more on this see Why Does Moss Grow In Lawns?

Pesticides Kill Microbes

“If your lawn has lots of weeds, consider the use of heat, vinegar, or manual labor to get rid of the weeds. If you use chemicals, follow it with compost tea. The microbes in the tea will immediately start to detoxify the soil by breaking down remaining chemicals“

Heat and vinegar do not kill plant roots, but they will damage grass as well as weeds. Vinegar Weed Killer Myth

Why add tea? The food soil web theory says that any chemical applied to soil kills all the microbes. After a chemical treatment the soil has no microbes – so you need to add them back in. The solution is that you add tea which is teaming with microbes. For some unknown reason, the chemicals kill all the microbes in soil, but don’t kill the microbes in the tea! These must be very special microbes. Not only are they immune to the chemicals, but they are able to break down the chemicals and detoxify soil.

Why are compost tea microbes so special? THEY ARE NOT!

The reality is that most chemicals sprayed on soil will NOT kill all the microbes. Even if they kill a few, there are many billions in every scoop of soil that survive. Bacteria are exceptional in their ability to eat (break down) just about every chemical including things like oil.

Your native microbes will help take care of any pesticide sprayed.  Weeding manually is a better option than pesticides.

Mycorrhizal Fungi

“Before planting, inoculate with mycorrhizal fungi”

The scientific evidence does not support the use of mycorrhizal inoculants on transplants. Most landscape soils already contain the fungi, or the soil is not suitable for the fungi to grow. Adding an inoculant will not help the latter situation. For more details see Mycorrhizae Fungi Inoculant Products.

Measure Rhizosphere pH

“Measure your soil’s pH in the rhizosphere.”

When talking about appropriate pH for plants it is important to talk about the pH of the rhizosphere. The above suggestion that the gardener should measure it, makes no sense. The rhizosphere is a 1mm thick layer of soil and water around the roots, and requires very special equipment to make any kind of measurement.

Gardeners have no way to know what their rhizosphere pH and soil labs won’t measure it for them.

Soil Food Web Eliminates Weeds

“soil food web gardeners need never worry about weeds again, which are the result of using high concentrations of nitrate commercial fertilizer”

It is true that adding nitrogen fertilizer to soil will increase weed growth – it increases the growth of every plant. What is false is that only commercial fertilizers have this effect. Adding any nitrogen source – organic or commercial has this effect. Remember plants can’t tell the difference.

The reason the soil food web system produces less weeds is that they also recommend using a mulch. Mulch keeps light away from weed seed, preventing them from germinating. This happens in every garden even those that do not follow the soil food web system. It also happens in gardens that mulch and use commercial fertilizers.

Reduced weeds is not a result of getting the bacterial to fungal ratios correct or getting the NH4 to NO3 ratio correct, as claimed. Mulch works this way on every soil.

The Miracle of Compost

“To inoculate your soils, put ¼ to 1 inch of compost around your plants. Compost can work its magic in as little as 6 months – new life will be evident down to 15 inches providing the benefits of decompaction, aeration, better water retention, and increased nutrients. After a year, the soil life will be down to 18 inches.”

Compost is great for the garden, and overtime it will do all of the things mentioned. But a ¼ inch of compost will NOT decompact your soil down to 15 inches in just 6 months. That is a ridiculous claim.

If the claim was correct, every garden would have great soil after only one application of compost. The reality is that adding compost yearly will make good soil after 10 years, and rarely will it be down to 18 inches.

The claim seems to stem from the notion that adding a few microbes to soil will suddenly change things. It won’t. If the soil is compacted and lacks organic matter, adding microbes will do almost nothing. You need to add the organic mater back to the soil and this is done over many years. The organic matter will feed the microbes which will slowly start to populate the compacted soil, and decompact it – this is a slow process.

The advice of adding a 1 inch layer of compost every year is great. Just don’t expect sudden changes. Nature does not work that way.

 

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Robert Pavlis
Editor of GardenMyths.com
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

11 Responses to 'Teaming with Microbes – A Close Look, Part 2'

  1. Ralph Lett says:

    So if humus does not exist do you believe that all composts are equal or do you prefer a certain type of compost over another ?

    • Composts are fairly similar. They consist of organic material that needs to break down. Once they break down they all produce the same thing – nutrients for plants. Some have a bit more of one nutrient, and others have less.

      The best compost is the one that is cheapest. Cheap usually means less processing and less trucking. Both of which are good for the environment.

      But you do need to watch things like sodium levels. For example some mushroom compost has high salt levels.

      • Ralph Lett says:

        If that is the case then you you would have no trouble in spreding composted bio waist all over your vegetable garden ? Bio waist is very cheep …

        • Provided that the bio-waste is properly composted and tested – I would have no problem.

          In this case it is important to test it heavy metals.

          A very large % of the population in the world uses human waste for growing food. We have been doing that for thousands of years.

  2. Bobby says:

    U claim compost tea does very little for soil life. Yet millions of organic growers use them ALONE to feed theyre plants. Comfrey? Popcorn? Earthworm castings.The list goes on the teas u can use at different stages of life. To claim they pretty much won’t benefit your soil is Purely False imo. Then u claim mycorrhizal really has no benefit Cause soil life already has it. Another claim i laugh at Mycos come in two forms endo and ecto one is for hard wood species like trees and one is for soft tissue species. Do the test yourself innoculate the roots of a transplant with mycos then plant one in your precious soil. The difference Will be mine growing and rooting much faster. Why i just cut the corner and instead of my plant searching for it its right there to create the symbiotic relationship. NO HUNTING for it in the dirt. Cation Exchange capacity when understood will kick the living horse crap out of synthetics based on chelating of compounds and holding them in the solution instead of draining right into the water table and then into our streams etc. OR is that false also???? And Compost contains humus its just not PURE humus cause that is compost that has been broken down even further

    • You have clearly been reading a lot of the organic propaganda and I can’t blame you for believing all these things. Many seem very logical and have strong proponents. I would ask one thing – look for the scientific evidence that supports these ideas. You won’t find it.

      You say that millions of organic growers use teas and that there are many concoctions, “the list goes on” you say. Why is it that with so many concoctions, no one has been able to show that one is better than the rest? Why has no one been able to show, in a scientific setting, that compost tea works better than compost?

      I have now spoken to three university professors who specialize in mycorrhizal fungi – they all agree, the commercial products are not needed. If you really believe you need to add more fungi, then take some soil from a local wooded are and use that. A better product and it is free.

      Interestingly you have made a number of claims – but you did not present one reference to back up your claims.

      Humus does not actually exist. Read http://www.gardenmyths.com/humus-does-not-exist-says-new-study/

  3. David Joly says:

    Hi !

    Interesting blog ! Would you recommend a better book/document about soil organisms, fertility and gardening/agriculture ?

    Thanks,

    David

  4. rogerbrook says:

    I makes me cross when so much rubbish is peddled around and believed by the gardening public. Out two countries are the same – no public sources of accurate horticultural knowledge – right up to government level!
    Keep up the educational work Robert

  5. Marnie Lett says:

    Hi! So if compost is all that in the end… What about humus? Same as compost or different? Thanks! M

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