Microscopic cells called "mycelium" -- the fruit of which are mushrooms -- recycle carbon, nitrogen, and other essential elements as they break down plant and animal debris in the creation of rich new soil. "We can capitalize on mycelium's digestive power and target it to decompose toxic wastes and pollutants (mycoremediation), catch and reduce silt from streambeds and pathogens from agricultural watersheds (mycofiltration), control insect populations (mycopesticides), and generally enhance the health of our forests and gardens (mycoforestry and mycogardening)."
Some of those nutrient deficiencies are kind of pretty! Although I imagine they won't help with fruit and vegetable production!
I think mycorrhiza have a big role in phosphate transport into plants, and that in general we've overfertilized with phosphates, causing depletion of those fungi.
You make a great point about soil building. I read that a good mycelial population holds soil in place, makes it drain better as well as hold moisture better, due to increased sponginess. A good cellulosic/lignin mulch - wood chips, chopped straw, chopped leaves - might promote mycelium. Also, somewhere I read the mycelial substances put a lot of carbon into the soil, so it's not in the atmosphere, which is a good thing too.
Resurrecting this discussion.... Here are a few links on mycorrhizae from recent news.'"
The pics here are mushrooms I photographed in my yard today. I don't know if they are beneficial, or mostly degrading organic matter, or benefit plants. I suspect some are beneficial because of their proximity to healthy trees.
From Yakima Herald, "Plants use fungi to communicate": "mycorhizae fungal hyphae increases nutrient and water intake as much as 100 to 1,000 times more than plant roots could. In return, plant roots release carbohydrates for mycorrhizal fungi to use for food. Since fungi cannot make their own food because they lack chlorophyll and live underground, it becomes a good deal for both fungi and plants." I don't know where they get that figue of 100 to 1000 X better nutrient and water intake. It sounds interesting. I imagine it depends on the plant type, the soil, and the type of fungi.
They also state, "How effective these plant/mycorrhizae mutualistic systems thrive depends to a large degree on how you care for the soil under your lawn, trees, shrubs, flowerbeds and vegetable garden." They state, avoid tilling. The advice is, limit soil disturbance to the top one inch. Use mulch generously.
The article states that mycorrhizal inoculants will not help,
I can see that. Fungi spread directly, buy extension of the fungal filaments, and indirectly, by spores. Thinking about the spores, just leave a piece of bread out. It will quickly get moldy. So some types of spores are everywhere.
From "Manitoba Cooperator": ". The old idea that tillage destroys the mycorrhizae is not entirely true, ... “In Western Canada, tillage is no more than eight centimetres. That has very little impact on mycorrhizae. In other areas, where farmers till deeper, with more aggressive implements, mycorrhizae are suppressed.” I don't know why the earlier article states till only one inch. Is that evidence based?
The glycoprotein that mycorrhizal fungi produce, Glomalin, is thought to contain 1/3 of the world's soil carbon storage. " it permeates organic matter, binding it to silt, sand, and clay particles. Not only does glomalin contain 30 to 40 percent carbon, but it also forms clumps of soil granules called aggregates. These add structure to soil and keep other stored soil carbon from escaping." That says to me, activities that support underground fungal growth are beneficial to the environment and would be helpful for the global climate change issue.
From wikipedia on glomalin, " When AM fungi are eliminated from soil through incubation of soil without host plants, the concentration of GRSP declines. A similar decline in GRSP has also been observed in incubated soils from forested, afforested, and agricultural land and grasslands treated with fungicide. Concentrations of glomalin in soil are correlated with the primary productivity of an ecosystem.
One thing I wonder about, is how to enhance mycorrhizal fungi in the artificial situations of our gardens. In the native soil, my thought is lawns, if one must have them, should be mowed fairly high, and the grass clippings left to decompose in place. That would mulch the grass. Around trees and shrubs, there should be larger areas of mulch, preferably organic mulch such as leaves, straw, wood chips, compost, or bark mulch. In raised beds.... I speculate that once the bed is built, fungal populations should increase with time. The soil in the beds should contain at least some native soil - to supply inoculum of local fungi, as well as generous amounts of compost. When possible, the surface should be mulched.
My raised beds are still fairly new. I started building them last summer. I did use the commercial inoculant mentioned earlier in this discussion. I don't know if it helps or not. As the soil settles, I add more compost on top and let the earthworms work it in.