Soils need all kinds of fungi, not just mycorrhizal types. Here are some reasons why.

Updated: Dec 19, 2019

Soil fungal hyphae, aerobic, beneficial fungi.
Free-living fungal hyphae in compost. 400x tot. mag.

Pick a fungal-inoculum product off the shelf. Unless it’s the work of a boutique or specialized producer (like this one), the product you’ve selected contains only mycorrhizal fungi -- anywhere between one and a dozen-or-so strains. And maybe a Trichoderma species or two.

What do these fungal types have in common? They are all plant symbionts, depending for survival on plant roots into which they can grow. These are the fungi that have evolved over billions of years to consume the carbon secreted by plants, meanwhile digesting from the surrounding mineral and organic matter an array of soluble nutrients to feed back to their partner plants.

The entire inoculum market is composed of only a few-dozen of the hundreds of species known to exist in healthy soil. To rely solely on these products for microbial inoculation, therefore, is to ignore the vast benefits unlocked by our understanding of microbial ecology. In better understanding how the microbial world works together, and therefore how our farm fields work (or should work), we can’t leave out the many thousands of species of free-living fungi estimated to exist out there. They all play some role in their own microbial ecosystems, and therefore play direct and indirect roles in plant health.

The following are some good reasons for including free-living fungal types in biological remediation.

Bacterial-Fungal Competition

To reproduce the organism communities that thrive in our own regions, we sample local soils and develop those microbes on a diet of diverse organic materials (basically, composting). Quick bacterial development, and the resulting heat, are important to the process, and newly ‘cooked’ material will almost always be dominated by bacteria.

Soil Fungi, testate amoeba, bacteria in compost sample.
Free-living fungal hyphae (diag. and center-left), testate amoeba (center). Compost sample. 400x tot. mag.

Bacterial communities are great, but we need fungal development too. Bacteria and fungi are nature’s two decomposers, the only organisms that make the enzymes necessary for breaking organic and mineral materials down to their constituent compounds. As such, there is well-documented competition between the two for resources. Given enough time, fungi will overcome bacterial dominance, aided by bacteria-feeding microbes like protozoa and nematodes.

What can we do to give fungal development a boost? Simple: inoculate clean composted material with free-living, saprotrophic fungi. For this application, we can’t use plant-symbiont types because our stored inoculum