I've done some reading on fungi and microbes in the last year, but I'm still somewhat confused by it all, so if this question makes no sense, my apologies.
My friend tells me that it is the plants giving sugars to the mycelium that causes the mycelium to generate/excrete glomulin and this "builds topsoil".
1. Is this true?
2. If it is, are there certain plant species and mycelial species that are known to work together to build topsoil faster than average?
I suspect it's no where near as simple as this, but if there are some "Three Sisters" version of the mycelial/topsoil building super-hero supersize combo, my friend wants some because he figures farmland has lost topsoil feeding him and he really wants to try and give some of that back!
Great question! Yes! Non-mushroom-forming arbuscualar mycorrhizae produce glomalin, a sticky protein that "gloms" soil particles together, turning dirt to soil and creating the tilth we love. It is a very stable and degradation-resistant comound, lasting ~50 years in the soil. This protein directly contributes to increasing aerobic conditions in soils and is only produced by these fungi.
These fungi are ubiquitous around the world and can be cultivated with a range of plants to increase their abundance and improve soil health. Soil tilling and over fertilization destroy these fungal networks.
See the 700-page Radical Mycology book—a compendium of all things related to fungi, their cultivation, and application—here: http://bit.ly/rmchthaeus
Here are more questions: In an existing 1/4 acre orchard which has mostly grass under it which is mechanically cut, but which has not been fertilized or tilled in over 10 years, do you feel that suitable mycorrhizae should be present?
Would adding tree guilds to each existing tree (like berry shrubs, comfrey, strawberry plants) increase the amount of glomalin those mycorrhizae produce?
Would adding a nitrogen fixing shrub (like goumi - Elaeagnus multiflora) help or harm the process of encouraging the mycorrhizae?
I know we aren't allowed to ask for references on Permies, but if you know of reliable research that supports this concept, it would be worth knowing about. Somewhere we have a specific thread asking about what research we need to be doing, and this strikes me as an area of "real-life" research with tests beneath trees grown traditionally vs trees grown with various supporting undergrowth and would support the Permaculture principles at the soil level.
In this situation, are there tests which could be done on the orchard, then we make certain changes, and then re-test to get some indication if we've increased or decreased chemicals that we tested for? I have one contact with a local University, so I might be able to get some support for this idea.
Helen A. Violi, et.al. published a paper in 2007, "Density dependence and interspecific interactions between arbuscular mycorrhizal fungi mediated plant growth, glomalin production, and sporulation" In the Canadian Journal of Botony.
Much of their research was done at the University of CA, Riverside and you should be able to get the whole paper there.
They found one thing that was particularly interesting; growth rate of plants and Up take of P, Zn and Fe were found to be reduced when Glomus intraradices and S. heterogama interacted.
"relative to plants inoculated with G. intraradices alone. Thus, for plant growth and nutrition, no evidence for functional complementarity was detected. Instead, interspecific interactions between mycorrhizal fungi resulted in a negative feedback on plants. Under high available P, fungal functional differences were reduced, whereas the overall difference between mycorrhizal and nonmycorrhizal plants was greatest. Overall, S. heterogama produced more glomalin than did G. intraradices. In a mixture, sporulation of the inferior mutualist, S. heterogama, was lower than that of the superior mutualist, G. intraradices, but interspecific fungal interactions increased the sporulation of both fungi. Despite the negative impact of interspecific interactions on plants, supporting multiple arbuscular mycorrhizal fungi was of greater benefit than being nonmycorrhizal."
In our orchard we have multiples of guild plants both under and between trees, which show signs of benefiting from both the mix of N fixing plants (we are using clovers and alfalfa) and the current density of mycorrhizae in our orchard soil seems to be helping the tree growth and fruit set/hold.
We also have started to put in raised beds for more vegetable production between the orchard trees drip lines, we do not anticipate any negative issues arising from doing this.
Next month I will be pulling plug samples to gather mycorrhizal and worm density data as well as nutrient makeup data.
We do not use any "chemical" fertilizers on the farm but we do use Fish Emulsion, Bone meal, Sea-90 and compost.
I would expect mycorrhizae to increase in both numbers and functions where N fixing nodules are present in the sub surface soils. We had a two fold increase in mycorrhizae numbers in the two places where we grew crimson clover last year, this was allowed to go to seed and die off/ collapse to the soil surface on its own.
This year it has come back nicely and the soil has 15.5:1 cm3 density ratio of mycorrhizal fungi