July 11, 2020 4 min read

In recent decades, numerous studies about soil microbes have revealed their complex functional mechanisms in and around plant root systems, as well as their positive and at times negative influences on soil and plants. Thanks to the effort of many researchers in the relatively new field of pseudo-fertilizers, professionals and home gardeners alike have come to recognize the potential of products based on soil microbes as alternatives to conventional fertilizers. Mycorrhizal fungi, in particular, have been singled out for their potency amongst other soil microbes, resulting in their wide penetration of the market. Now everywhere you go, you can easily find a commercial mycorrhizal product without breaking a sweat.

What about mycorrhizal fungi is so effective that it has catapulted their status to microbial stardom? Let's start unpacking by first establishing the two different classes of mycorrhizae- Endo Mycorrhizal Fungi (Arbuscular Mycorrhizal Fungi, otherwise known as AMF) and Ecto Mycorrhizal Fungi. We will primarily focus our attention on AMF, since this type of mycorrhizae holds more weight in agriculture and gardening. According to one of the leading manufacturers of mycorrhizal products, “the key benefits among many others that mycorrhizae provide to professional growers are: root system enhancement, improved nutrient efficiency, and increased water absorption & utilization.” True to its description, most commercial brands market their mycorrhizal products as ‘root boosters’ and ‘growth promoters’, often paired with photos of abnormally large roots balls of plants. Thanks to years of repeated marketing efforts of these brands, almost everyone who buys mycorrhizal products have come to hold high expectations- ones that anticipate miraculous results in plant/crop/grass growth and yields. Fortunately for these buyers, mycorrhizal fungi have proved themselves to be up to the task, showing time and again their success in boosting plant growth and yields, to the point where it’s no longer a question whether they are effective or not.

As cultivators of soil microbes, we, at Microbial Applications, Inc. also understand the important role that mycorrhizal fungi will continue to play and expand in the upcoming agriculture and gardening industries. We also believe that it is our role and responsibility to deliver the true nature and potential of this miraculous fungi, beyond the pervading marketing messages and slogans currently dominating the market.

So without further ado, let us dig further into what other functions mycorrhizal fungi might serve. First, plants have two ways of achieving nutrient uptake- direct and indirect. Necessary nutrients are partially absorbed directly from the soil by plant roots through diffusion, while the rest are indirectly fulfilled by AMF. "How?" you might ask. Once inoculated to a plant, AMF penetrate the cortical cells of roots and build a symbiotic relationship with the plant. Plants provide AMF with sugar produced through photosynthesis, and in return, AMF provide the host plants with nutrients in soil via fungal hyphae. Roots can only absorb nutrients in limited areas of the root zone, whereas the finer and thinner structure of fungal hyphae have better access to soil pores and can explore larger soil volumes, resulting in a more efficient and effective structure for mining nutrients including one key nutrient- phosphate. This is a mechanism already widely known to the public, and this is the very mechanism which has made AMF stand out among other microbes as an alternative to traditional fertilizers. However, the hyperfocus on this mechanism alone fails to take into account the full extent of what mycorrhizal fungi are capable of.

This brings us to our next point: most soils, in their natural state, lack phosphorus. This is due to the fact that phosphorous is fixed as insoluble iron and aluminum phosphates in acidic soils (particularly in soil with a pH lower than 5.0) or as calcium phosphates in alkaline soils (with a pH above 7.0). This is where other soil microbes such as pseudomonas, bacillus, aspergillus, Trichoderma, and penicillium play an important role in solubilizing ‘fixed phosphate’ into accessible phosphate in the form of H2PO4-(dihydrogenphosphate) or HPO42-(hydrogenphosphate). They do this by producing organic acids- gluconic, citric, oxalic, lactic, isovaleric, succinic, glycolic, acetic, etc., through chelation, and through mineralization via alkaline/acid phosphatases. AMF then absorb and transport the phosphate made accessible back to the roots for the nutrient consumption of the plant. 

Phosphate solubilization, or P solubilization capacity of microbes varies highly depending on nutritional conditions, already-existing microbial community in the soil, soil pH, and plant type, among many other factors. In theory, mycorrhizal fungi are not much more than transporters of nutrients. Further, the nutrients in soil will not be plentifully available unless other soil bacteria and fungi work to produce and make them available. In reality, however, mycorrhizae alone can also be effective, because most soils already contain microbes in their soil ecosystem, and because most people apply additional nutrient supplements when applying mycorrhizae. Nevertheless, all things considered, you have a higher chance of getting better outcomes when combining mycorrhizae with other beneficial soil bacteria and fungi, and this should always be kept in mind. When combined, different species of soil microbes interact with each other on a functional as well as a physiological level. One example of how this interaction manifests can be observed in the influence of AMF on the colonization of PSB (phosphate solubilizing bacteria). Another example is how Bacillus and Trichoderma come together to contribute to AMF propagation.

A graphic explaining some of the functions & processes of Mikro-Myco:

There are so many mycorrhizal products to choose from- some with only mycorrhizal fungi, and others with varying inclusions of non-mycorrhizae soil bacteria and fungi. Even with a large selection of choices, rarely have we seen brands combining considerable amounts of rhizobacteria and beneficial fungi with mycorrhizae. This was the logic behind the creation of our first product- Mikrobs, which contains significant amounts of AMF, Trichoderma, AND Bacillus, along with organic nutrients for microbes and plants. In Mikrobs, however, the leading player of the blend is PGPR (plant growth promoting rhizobacteria). For this reason, we decided to launch a different formula that focuses on mycorrhizal functions: Mikro-Myco. A primarily mycorrhizal product, it is comprised of an ideal combination of Endo Mycorrhizae (260 cfu/g), Ecto Mycorrhizae (218,000 cfu/g), Trichoderma (750,000 cfu/g), and Bacillus (400,000,000 cfu/g). We are proud to introduce Mikro-Myco to the market and we urge you to check it out!!

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