A Preparation For the Georgia Master Gardeners Convention
I almost always agree with Fukuoka. There are real limits to human knowledge, especially regarding what we can truly understand about nature. I don't think humans can improve nature, and most of our attempts to do so have the opposite effect. What we can do, however, is learn to imitate nature's design. If our attempts to understand the subtleties of nature lead us to build food systems more in line with natural ecologies, then I believe we are on the right path.
One of the areas of natural ecologies we have almost entirely overlooked in our food production systems is the role of fungi in the landscape. At the conference we will spend some time talking about growing mushrooms for the table, because hey, they are delicious and, despite the common American perception, extremely nutritious. Some of them are world-class medicinals, like reishi and shiitake. For example, in Japan shiitake mushrooms are not just some wingnut alternative treatment for cancer; they are the go-to medicine for all types of digestive system cancers. The government has officially held them in such high regard since 1985. How much more pleasant would a plateful of sauteed shiitakes be than chemotherapy? We will be discussing more about mushroom medicine at the conference, too. We'll also talk about the use of fungi in mycoremediation efforts - fungi that filter harmful levels of E. coli from runoff water, fungi that digest diesel fuel spills and jumpstart ecosystem regeneration, and a few other surprising abilities the fungi possess.
For the purposes of this article, though, we will focus on the most pressing myco-issue for gardeners: the role fungi play in the generation of living topsoil. Would it be an overstatement to claim that incorporating fungi into your garden plan is THE big secret to building healthy, living topsoil? The answer is an emphatic NO! I'm going to lay out a strategic circular pathway for significantly increasing the amount of humic substances (more commonly "humus") in your garden soil. These are the complex and recalcitrant carbon-rich molecules that persist in the soil for decades, even centuries, providing abundant sites for cation exchange, and the characteristic "blackness" of healthy organic soils.
The first question that is probably popping into a lot of heads right now is, isn't that what compost does? Yes, but not very well. Only 1-5% of compost is represented by the stable humic substances we're looking for. That's not all that much. For the moment think of compost simply as organic fertilizer. We'll get back to this in a minute, after we jump over to the big tamale.
What creates the bulk of our stable soil humus are the mycorrhizal fungi. This is one of the three major categories of fungi - along with the parasitic, and saprophytic fungi - and they form mutually-beneficial associations with the roots of living plants. The filamentous underground body of the mushroom that forms the bulk of its mass is called the mycelium. Ecto-mycorrhizal fungi grow around the roots of the host plant, while endo-mycorrhizal fungi invade the living tissue of the plant's roots. From Stamets: "In either case, both organisms benefit from this association. Plant growth is accelerated. The resident mushroom mycelium increases the plant's absorption of nutrients, nitrogenous compounds, and essential elements (phosphorus, copper, and zinc). By growing beyond the immediate root zone, the mycelium channels and concentrates nutrients from afar. Plants with mycorrhizal fungal partners can also resist diseases far better than those without."
These minerals, these cations, that are made more available by the associated fungi only become bioavailable to the plant if there are sufficient cation exchange sites to host the transactions involved, and those are, most commonly, provided by the molecules of humus that we are trying to build. The mycorrhizal fungi create these humic substances as a byproduct of carbon induction while mining new mineral fertility from the underlying subsoil and/or bedrock. And they create a lot of them. This is what the fungi do for the plants (and the rest of life on Earth in turn), and in exchange, the plants feed the fungi with exudates - sugary carbohydrates, amino acids, fats and lipids - from their roots. The more of these the plant produces, especially the fats, which are three times more energy dense than carbs and proteins, the more energy the fungi can tap to digest rock and create humic substances.
That's where the compost comes in. Compost provides a ready source of rapid-cycling carbon to feed the plants. The carbon bank in a compost application will mostly be used up within a few years, but it's the kickstart from which an organic system benefits enormously; although it doesn't, by itself, add much to the long-term durability of the topsoil. The compost makes happy plants, happy plants make happy myccorhizal fungi, and happy mycorrhizal fungi make loads of humus from the subsoil...which makes happy plants, which make...I think you get it. A positive feedback loop has now been established that will promote ever-happier and healthier plants in perpetuity. Until it's screwed up again, say, by cultivation and the aerobic acceleration of humic degradation, which is, unfortunately, (drum roll please) the crown jewel of modern agriculture. It's only a matter of time before food production methodologies that don't respect the fungi and their role in soil building will compromise every last acre of soil on Earth. This will be agriculture's lasting legacy...if there's anyone around to notice. Fungi can only dominate the soil, feed the plants, and create stable carbon, if they are left intact. Tillage destroys fungal networks, accelerates the decay of typically-stable humic substances, and creates the need for prepared fertilizers and pesticides. Remember, a plant growing in healthy living soil can take care of itself - just look at the nearest wild forest. Are people fertlizing it and spraying to control pests and disease? Cultivation is where we really messed up as a culture. That and generally disrespecting the fungal components of our ecosystem. Now we know better.
Use your knowledge of this cycle to become an unstoppable master gardener. People who can do this stuff, who can repair the damage agriculture has wrought upon the landscape, will be tomorrow's leaders. About that I have no doubt. The only way that wouldn't be true is if everything just fell apart, and the global population collapsed, leaving many more acres per capita to the remaining human population. We created our current population by mining our topsoil's capital resources - mined ever-faster on the back of oil - and those resources are dwindling fast. Even the mainstream agricultural establishment is starting to talk about this problem! Our charge, as the younger generations alive today, the only task before us really (except perhaps nuclear decommissioning), is the rebuilding of the world's topsoil. Without it, none of the other peak issues we face today will even matter. Rebuilding the world's topsoil will automatically restore the dying freshwater cycle. Both of these dire situations are part of the same systems failure that is becoming more obvious by the week, but, luckily, the repair of one initiates the repair of the other. In my opinion this is THE task before us in the 21st century. Renewable energy, social justice, there will never be enough to matter until we get our mineral cycles - the topsoil, atmosphere, and freshwater cycles - back in order. Praise the people who tend to such items, theirs is a noble endeavor, but the folks who can restore topsoil will rule the contractionary future. And there is room for all of us in this task.
Growing Gourmet and Medicinal Mushrooms and Mycelium Running, both by Paul Stamets (Ten Speed Press, 1993 and 2005, respectively) are indispensable resources for all things mycological.
"Changing Dirt Into Soil" by Michael Martin Melendrez, Acres USA, October 2011.
"Carbon Building, Carbon Cycling" by John Kempf, Acres USA, October 2011.