John Kempf explains how to build a healthier soil microbiome: plant diversity matters most, applying microbial inoculants at seeding gives the best return, and low-rate applications actually work despite what skeptics claim. He points to rhizobium on legume seeds as proof that even single-strain inoculants succeed.
Chapters
What are the most effective and practical steps for improving soil communities? Number 1 is plant species diversity, plant family diversity. Soil microbial community doesn't thrive well in a monoculture, or maybe a better way to say it would be that it becomes very specialized in long-term monocultures, which usually isn't associated with optimal soil health, at least not from an agricultural perspective. You can add microbial inoculants when seeding. That is the greatest ROI application that we see consistently for across almost all types of applications. Putting on a plant or putting on a microbial inoculum at seeding is critical. And then what are the myths to watch out for? Well, two big ones that I see. One of them is targeted towards compost tea applications, and one of them is towards purchased inoculants. The one myth is that putting on a purchased inoculant at small application rates of a few pints or a quart per acre— actually, in this case, this myth is also extended to compost tea— is that whatever you apply out there is meaningless and it's going to be consumed by the native soil ecology and microbiology, and it will disappear in a matter of hours or days or weeks and have no effect. I beg to differ. And I would suggest that the evidence also has a different perspective because you look at the history of the use of mycorrhizal fungi or of the use of rhizobium bacteria. I mean, it's, it's common industry standard practice to inoculate legume seeds with one single strain of bacteria, rhizobium. And that's an application of tiny amounts of a single species inoculant that is effective. So that's one myth. Another myth, I kind of already addressed it with Rhizobium, but another myth is that a purchased inoculant with only a few strains cannot be successful. Rhizobium is Exhibit A, mycorrhizal fungi inoculants are Exhibit B. There's a number of others. Yes, single species, single strain, It's not ideal. It's not how nature works. Generally, it works in consortiums and in communities, but single species can be impactful and they can make a difference. And products with only a few strains in them can also be very impactful. Another common myth, um, most compost teas and most purchased inoculants do not address 95% of the soil microbiome. Why? The very simple reason is that the majority of the microbiome can only be propagated in the presence of living plant roots. Not in a compost pile and not in a laboratory unless the laboratory is growing plants to propagate microbes. And there are some laboratories that do. That's how BioCoat Gold, some of the materials and source materials in BioCoat Gold get propagated. So actually growing plants in compost piles and doing those types of things as the second stage of inoculant development, I think are very important.
