Inorganic fertilizers disrupt mycorrhiza / Pascal Pernot culture sheet on AOS

[MateoinLosAngeles]

Hey everyone,

I was reading this Caledonia care sheet authored by Pascal Pernot, which mentions a recommendation to add blood meal to the potting media as "inorganic fertilizers are known to disrupt the mycorrhiza."

Is there any truth to that or is it a sweeping statement more aligned with demonization of anything synthetic?

E.g. can one use a high nitrogen synthetic fertilizer (K-lite has similar NPK % as Blood Meal, a clear analysis of many micronutrients) and supplement it with Bacillus subtilis? When you google organic fertilizers most only list the NPK value, no listing of micronutrients or microbiological strains. Also, no guarantees that the manufacturing process doesn't affect the microbiology. Should we assume that after so many viruses have jumped from bats to humans, bat guano doesn't go through a high-heat process to eliminate pathogens that also eliminate beneficial bacteria?

It's worth noting that Pascal Pernot has an extensive career documenting and writing about terrestrial orchids, especially those found in France. However, doesn't cite any scientific works to back his claim on the AOS website. Neither do we know if his documentation process has also translated into a successful orchid growing career.

What are your thoughts? Is this a myth to be busted?

[isurus79]

I know that organic gardeners have been parroting the idea that synthetically derived fertilizers are somehow detrimental to the microbiome garden for a while. We know that is incorrect. I suspect the fungi in our orchid pots are similarly unaffected by synthetically derived fertilizers, but I can't point to any papers indicating as much.

[Dimples]

The idea isn’t completely far-fetched, but it has definitely been twisted somewhat over time. Bacteria and fungi utilize organic fertilizer (any complex organic molecules nearby) in their own metabolism, and by doing so, they also unlock the complex nutrients and convert them into the simpler, plant useable forms. If you never add organic fertilizer (or raw/partially processed organic materials) to your garden or mono-cropped farms because you’re already directly adding the plant-available-forms of fertilizer, then over time as the microbes use up what material already exists, the environment eventually has very little food available for the microorganisms and their populations will decline. If the system lacks complex nutrition sources for a long time, the microorganisms can become all but nonexistent in that area. It’s possible that high concentrations of specific soluble fertilizers has a direct effect on microbe populations, but I haven’t looked into it for a few years.

Outside in the ground, this is a bad thing. Less biodiversity, less nutrient cycling, fewer symbiotic relationships happening in the root zone, so overall the plants won’t be as healthy or robust, and neither will the local environment.

Maintaining a robust population of microbes in a small pot isn’t easy, and makes feeding your plants with organic fertilizer a lot less predictable. As temperatures and moisture levels change, so does the population of microbes and their fertilizer processing abilities. You never truly know what % of the organic fertilizer gets converted vs lost, so making adjustments isn’t as easy if you start seeing problems. It’s not impossible if the pot is larger enough, but the larger the average particle size in the mix, the harder it will be for the microbes to establish themselves and stick around.

The older idea that the production process for organic fertilizer is better for the environment vs synthetic, is not as true as it once was. Mining naturally derived minerals on another continent, shipping them globally, and all the rest, now means non-local sources of organic fertilizers can be equally as destructive to the environment as the production of synthetic fertilizers. So, if eco-friendly choices are important to a grower, it’s doubly important to know the production history of the products.

I’m an organic farmer and I use synthetic fertilizer on my indoor plants because over time I’ve determined that it’s the choice with the fewest environmental downsides for my scale.

[Ray]

I have anecdotal evidence that bacteria can utilize inorganic fertilizer- The Exxon Valdez oil spill.

I spent most of my career working for the French petrochemical company, Elf Aquitaine, now known as Total Energies, courtesy of mergers and acquisitions (the company actually had 8 different names during my career).

If you work with oil, there will be spills.

At the time of the Prince William Sound spill, the state of the art was to inject oil-eating “super bugs” (bacteria) into the spill. That worked, but not very well, as they were not native to the Alaskan environment and were predated by indigenous species.

Scientists at Elf found that if you emulsify a high-nitrogen fertilizer with the cheapest olive oil available and sprayed that on the spill, the (inorganic) nitrogen sparked an explosion in reproduction of the native microbes, aided by the easy-to-digest source of carbon, the olive oil. Once that had been consumed, that mega-population went to work on the spill.

Six weeks after they sprayed 1.5 miles of coastline, there was no trace of the oil, and unlike those areas that were steam cleaned, the ecosystem remained alive.

We even formed a business unit based upon that, targeting train yards and any other place where oil is commonly dripped/spilled.