Ask A Farmer — The Fungus Among Us

ask a farmerBy Andrew Plack

The fungus is among us. In fact life as we know it would be impossible without fungus. Fungus is theorized to be the seed of life in the universe. Spore capable of surviving in space may be the colonizers of planets. Life may be fungus based from the start. The theory is that as objects smash into earth, spore are carried up out of the atmosphere and scattered across space. If this is so, then aliens are with us already.

Fungi are everywhere – beneath your feet, almost everywhere you look, and even in the air you breathe. Without these strange  life forms, neither we, nor the rest of life on earth would survive for long.

The interest in organic gardening has stirred a deeper knowledge of soil life. We know now that most fungi live in partnership with our garden plants in an unseen symbiosis. The  threadlike strands, the mycelia, of each organism effectively extend the root system of trees, shrubs and virtually all other plants. The plants feed the fungi sugars, giving them the energy to produce fruiting bodies, (mushrooms.). The fungi deliver nitrogen and other nutritious elements to the plants. 

Fungi are not able to ingest their food like animals do, nor can they manufacture their own food the way plants do. Instead, fungi feed by absorption of nutrients from the environment around them. They accomplish this by growing through and within the material on which they are feeding. Numerous hyphae network through the wood, cheese, soil, or flesh from which they are growing. The hyphae secrete digestive enzymes which break down the substrate, making it easier for the fungus to absorb the nutrients which the substrate contains. This filamentous growth means that the fungus is in intimate contact with its surroundings Most fungi are saprophytes, feeding on dead or decaying material. This helps to remove leaf litter and other debris that would otherwise accumulate on the ground. One calculation has us all buried under leaf litter, circling the globe without the interaction of our fungal friends. Nutrients absorbed by the fungus then become available for other organisms which may eat fungi. Most Plants on earth rely on a symbiotic fungus to aid them in acquiring water and nutrients from the soil. The specialized roots which the plants grow and the fungus which inhabits them are together known as mycorrhizae, or “fungal roots”. The fungus, with its large surface area, is able to soak up water and nutrients over a large area and provide them to the plant. In return, the plant provides energy-rich sugars manufactured through photosynthesis.

Mycorrhizal fungi are able to absorb and transfer all of the 15 major macro and micro nutrients necessary for plant growth. Mycorrhizal fungi release powerful chemicals into the soil that dissolve hard to capture nutrients such as phosphorous, iron and other “tightly bound” soil nutrients. This extraction process is particularly important in plant nutrition and explains why non mycorrhizal plants require high levels of fertility to maintain their health. Mycorrhizal fungi form an intricate web that captures and assimilates nutrients in soils. In non mycorrhizal conditions much of this fertility is wasted or lost from the system.

Mycorrhizal relationships are fascinating partnerships that take place when the hyphae of certain fungi wrap around, or penetrate the roots of a plant, whereupon a mutually beneficial exchange takes place. The fungus, which cannot obtain energy directly from the sun itself (as it lacks the chlorophyll found in plants), is able to obtain sugars that the plant produces using photosynthesis. In return the fungus provides the plant with vital nutrients that it extracts and transports from the soil, and that would otherwise be unavailable to the plant. Surprisingly, most of the plants in virtually all of the world’s terrestrial ecosystems rely on these relationships for their healthy growth. It gives some perspective on the importance of fungi when we consider that without them the world’s forest ecosystems would collapse. So what is natural is a dynamic community that works together as a whole. Nature is a whole, dynamic and ever adjusting relationship between all of life. The fungus along with the plants, all cycling air, water and nutrients around the environment.

Mycorrhizal fungi are key players involved with a wide variety of other functions that benefit plants and humans. The same extensive network of fungal filaments important to nutrient uptake are also important in water uptake and storage. In non-irrigated conditions, mycorrhizal plants are under far less drought stress compared to non mycorrhizal plants.

Disease and pathogen suppression is another benefit for a mycorrhizal plant. Mycorrhizal roots have a mantle (a tight, interwoven sock-like covering of dense filaments) that acts as a physical barrier against the invasion of root diseases. In addition, mycorrhizal fungi attack pathogen or disease organisms entering the root zone. For example, excretions of specific antibiotics produced by mycorrhizal fungi immobilize and kill disease organisms. Some mycorrhizal fungi protect  trees from Phytophora, Fusarium and Rhizoctonia diseases and attack. In a recent University study, trees were purposefully inoculated with the common disease organism- Fusarium. Over 90% of the trees died. Only the trees inoculated with the mycorrhizal fungus Rhizopogon survived. Survival rates for Rhizopogon treated trees exceeded 95%.

Mycorrhizal fungi also improve soil structure. Mycorrhizal filaments produce humic compounds and organic “glues”  that bind soils into aggregates and improves soil porosity. Soil porosity and soil structure are key for the growth of plants by promoting aeration, water movement into soil, root growth, and the ability to distribute. In sandy or compacted soils the ability of mycorrhizal fungi to promote soil structure may be more important than the seeking out of nutrients.

When we alter  the conditions that beneficial fungus need to live, we reduce the capacity of the land to grow plants and trees. As we affect the health of the mycrorysomial interfaces in a negative fashion, we reduce the plants ability to feed. The next thing that may happen is we see distress and add more inputs, many of which may speed up the destruction of the total health of the plant  fungus symbiosis.  This basic destruction of fungus and bacteria leads into a downward spiral of productivity in our orchards and gardens. Plowing, or turning the soil exposes fungus to light, something that can be deadly to our ally. In fact a healthy garden doesn’t look like a clean room, instead there is a bit of leaf litter and plant debris on top of the soil. This layer protects the fungus and bacteria from sunlight, as well as becoming a food source and weed suppression layer. If you just call it green mulch, you can feel that you are still an orderly human.

Soils in natural settings are full of beneficial soil organisms including mycorrhizal fungi.  Many common practices can degrade the mycorrhiza-forming potential of soil. Tillage, fertilization, removal of topsoil, erosion, site preparation, road and home construction, fumigation and leaving soils bare are some of the activities that can reduce or eliminate these beneficial soil fungi. In many man-made landscapes we have reduced or eliminated the soil organisms necessary for plants to function without high levels of maintenance and inputs. This condition worsens over time and can lead to dramatic events like the dust bowl years of the southwest in north America.

When we keep in mind the nature of plants and their relationship with fungus, it seems obvious that farming and gardening , knowingly or unknowingly , involves the health of fungus. There are of course pathogenic fungus, but a healthy soil is a whole community and working towards the total health of the soil is simply the best approach to long term productivity. When your garden beds have fine white threads of mycelium, (or even better fruiting mushrooms),it is a good indication that you have healthy soil.

There are mushroom kits for garden beds. Growing mycorrhizae and even edible mushrooms right in your growing beds not only gives another crop in a tight space, but ensures that the soil structure is maintained and makes nutrients readily available for your vegetable crop. Unlocking nutrients in the soil is the real key to soil fertility, as adding petrochemical inputs can burn and destroy micro organisms. This effect is that in the short term the plant looks greener, but by destabilizing the soil community , the effect is to invite unbalance and disease.

Other ways to boost mycorrhizae are  the use of pre-made IMO products, or you can learn to wildcraft your own from the areas close by that still are somewhat undisturbed.

If what we want is health and fertility, the only question becomes,”what is natural”. All answers lie there.

Happy garden, happy life.

(Andrew Plack farms in Hamakua.)

3 replies
  1. fruit farmer
    fruit farmer says:

    I can attest to this in my own organic orchard. I used to use chicken manure and dolomite mainly and got decent results, except that I still needed to hand weed acres of trees. since I have to mow a large area, I began to collect the grass to spread under the trees, usually half a foot deep. If my grass piles sat for awhile, it would be hot and grey inside from fungus. Now I have stopped using any fertilizer at all, and the trees are better than ever. And there’s almost no weeding. Under the rotting mat of grass is teeming with life, especially millipedes that are found in compost. Even in drought it stays moist, and mushrooms are coming up under the trees, even the pasture kind, proving that cows are not a necessary part of the loop for that mycelium. Another benefit is that rooting pigs no longer dig up tree roots, since they find all the worms they need under the grass layer. I am wondering if I still should use lime?

  2. fruit farmer
    fruit farmer says:

    Thanks Andrew, for the informative article. This may be one key argument in favor of non pesticide farming, since the use of chemicals could destroy the mycelium, making trees dependent on more chemicals. Mulch!!!!!

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