The Johnson-Su Bioreactor Enriches Beneficial Soil Fungi

Stop Turning Your Compost

Composting offers a terrific way to culture native microbes that benefit your soil. However, there is more to a good compost than simply building a pile of manure and yard waste. Proper aeration is important to prevent overheating and to ensure that aerobic bacteria-bacteria that consume oxygen, dominate the mixture.  While there are exceptions to every rule in the microbial world, aerobic bacteria are typically less pathogenic than the strict or facultative anaerobic species that thrive when oxygen is lacking.  Aerobic composts also smell better and attract fewer flies because they don’t produce the foul smelling organic acids and sulfur compounds that anaerobic composts generate.  This is a key reason many large scale composting facilities aerate their composts by turning it at regular intervals. Certain composters sold for home gardeners are also designed for frequent turning, and many gardening shows, books, and even extension agents will recommend that composts be turned.

Unfortunately, while turning does increase the abundance of aerobic bacteria (and that is good), it also shatters delicate fungal hyphae  (long filaments) before they can become fully established in the compost (and that is bad).  The reason you don’t want your fungal hyphae to break is because fungi are key to the establishment of a thriving soil community.  As decomposers, fungi build soil. They transport water and mineral nutrients they absorb from pebbles, soil particles, and dead stuff, and transfer them to plants in exchange for organic carbon compounds like sugars and amino acids. A fungus must reach a mature size, and extend its hyphae across several meters in order to maximize its ability to mobilize nutrients and reproduce.  The the bigger the fungal hyphae networks in your compost grow, the more nutrients they are able to extract and transfer from your waste material to the plants you hope to support.  A healthy fungal population will also decompose weed seeds in your compost, and reduce potential for pests and disease organisms that might otherwise dominate your compost.

A Johnson Su Bioreactor Provides Aeration and Moisture Without Turning

Dr. David Johnson of New Mexico State University has tackled the problem of producing fungal rich compost by designing a bioreactor that provides proper aeration and moisture without turning.   His design works well for small farms and household gardens.  It can also be upscaled for large commercial operations by simply maintaining the principles of including enough finely chopped woody material (straw, dry leaves, sawdust, etc) to feed fungi (fungi love a high fiber diet) and by providing adequate air and moisture without turning.  Watch the video below, contributed by David Johnson, to learn how this is done.  Dr. Johnson’s research is helping growers worldwide increase yields while building soil health and mitigating climate change, so you might also want to check out other videos on his YouTube Channel.

By means of disclosure, I know David Johnson, and consider him a colleague.  However, I have no sort of financial affiliation, and I get no benefit from sharing links to his pages. I value his message, and I share his perspective that we can use microbes to increase agricultural productivity, build food security, improve human nutrition, and combat climate change.

(The above video is used with permission from Dr. David Johnson.)

Putting the Bioreactor to the Test

We have evaluated David Johnson’s bioreactor on our own site in Southern New Mexico, and also at Schultz Family Farms in Longmont, Colorado.   The setup takes a bit of work, and requires quite a bit of starting material, so it is important to plan ahead.  While having adequate material on site is rarely an issue for farmers, home gardeners often build their compost using a few table scraps at a time, and the bioreactor needs to be filled all at once.

My advice to growers who don’t have enough material on hand is to wait until fall, gather at least a pickup bed full of dry leaves from your neighbors, chop them with a mulcher, and get started.  As for your table scraps, even if you have 4 or 5 teenagers in your home, it will be hard to generate enough leftovers to fill this bioreactor.  You will provide nutrients to your garden more quickly if you simply chop your food scraps into bite sized pieces and place them directly on your soil. Finely chopped scraps will dry quickly on the soil surface here in the southwest, and they are unlikely to attract pests or disease.   Of course, if you live in a more humid area, you will want to bury them a few inches below the surface to keep raccoons and other unwanted guests away.  Avoid placing perishable food wastes near plants that are close to harvest.  And if you are growing commercially, verify regulations with the appropriate state, federal, and organic certification boards.  Science and policy are not always well aligned.   I’ll expand on safe practices for mulching food scraps in another post.  

The video below, taken from bioreactor compost prepared at Schultz Family Farms in Longmont, Colorado, emphasizes one of many very long, dark septate fungi we found in the bioreactor only two weeks after we initiated the process.  A diversity of fungal spore types, bacteria, and protists are also visible in the video.  This is what you want good compost to look like under the microscope.



When Does a Bioreactor Make Sense to Use?

Now, a few very green minded growers I’ve spoken to have challenged the wisdom of using a leaf mulcher and going through all this effort to chop woody material and build compost, when microbes will eventually break it leaves down anyway.  I agree that microbes will do the job in time.  If all farms were currently using proper organic, permaculture, or regenerative approaches on quality land today,  and if all sites were free of environmental threats that inhibit plant growth, I would agree that a bioreactor may be more work than is necessary.  But the point of the bioreactor is not to simply build compost.  The point is to build a living culture of beneficial microbes, capable of supporting plant growth, soil health, and crop nutrition.  A composting bioreactor makes sense to maintain on any site that may be prone to pests, disease, heat waves,  or unexpected cold spells that challenge plant growth.  Why?  Because bioactive compost is a necessary ingredient for making compost teas rich in minerals, fungi and bacteria.  These compost teas can increase plant resistance and resilience to stress.

Don’t want to mess with teas?  Simply broadcast handfuls of finished compost on your soil prior to irrigation.  The microbes will migrate to your soil, and begin building.  If the bioreactor compost is applied in conjunction with other regenerative practices, and if soil organic matter is being maintained above 3%, one application may be all you ever need.  However, I like to keep a batch on site at all times as a sort of rescue remedy.

Seeds mixed with fungal rich compost are more likely to germinate and establish with minimal effort.  Compost teas can rapidly disperse microbes and nutrients on leaf surfaces to protect them from a wide range of environmental threats, including pest and disease outbreaks, heat waves, and cold fronts.

You can learn the fine details and best practices for making fungal rich compost by downloading BEST MANAGEMENT PRACTICES:
JOHNSON-SU COMPOSTING BIOREACTORS, by David Johnson and Patrick DeSimio, from the button below.  Yes, it is totally free.  No, we can’t take the credit for it.  The agencies and individuals who made the publication possible are duly noted within the pdf file.

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