Charles
I”m no expert on the subject, but I get the impression that fungi are most valuable for plants when soil and moisture conditions are particularly suboptimal, as the symbiosis allows the plants to access minerals and moisture from far greater areas than alone?
In market gardening situations where you replenish the soil with compost once a year, I would reckon naively that the absolute need for fungi was less, although of course they will still be beneficial.
My other reading suggests that the fungi can decrease in population if they go 3 months or more without plants to interact with, so if there is no winter crop or green cover, then there is the possibility over a few seasons for levels to drop far below what you might see with e.g. a grass-covered field.
Thus the use of fungi may be most beneficial for gardeners who cannot access large amounts of high quality compost every year for their vegetable patches??