The Efficacy of AMF Inoculants: Findings From the Sound Agriculture Lab

When our Research Scientists began exploring Arbuscular Mycorrhizal Fungi (AMF) three years ago, they set out on a mission to identify whether AMF inoculants could meaningfully improve crop performance and if so, what it would take to develop a product that consistently works in production agriculture.

These are their findings.

Written with expertise provided by Anne Kakouridis, PhD, Mycologist, Sr. Scientist, Sound Agriculture

Creating a reliable AMF product is challenging and there aren’t many available AMF products for large-scale agricultural use. 

So when Sound’s Research Scientists decided to explore the possibility of bringing a potent AMF product to the agricultural market, they knew they would have to make a significant investment in the vetting process in order to accurately evaluate AMF quality.

Starting from classic methods such as Oehl et al., 2003, the team developed an evaluation pipeline that converged on the same vetting methods used by leading academic labs and in recent academic studies such as Boussageon et al. (2025) and Koziol et al. (2024). Sound’s Research Scientists concluded that it was essential to use the same testing framework during their three year discovery process when evaluating the efficacy of existing AMF products on the market.

AMF quality is about more than just having ​‘spores in a bag.’ ​“AMF products are actually pretty tricky to make, and for a product to work it needs to have a lot of active spores,” notes Anne. Spores are living fungal propagules, and their ability to colonize roots depends on:

• The number of spores
• Whether those spores are alive
• Whether they can germinate
• Whether they can actually colonize a plant

To evaluate that, each AMF product went through five independent assays:

1. Propagule Extraction: Are there AMF spores?

Sound extracted AMF spores and colonized root fragments using sucrose density fractionation and wet sieving, the same core methodology established by Daniels & Skipper (1982) and still in use today.

2. Microscopy: How many spores are there?

Sound verified the number of spores per gram or mL of product (for powder and liquid formulations, respectively) — not just what’s printed on a label.

3. Spore Viability Assay (MTT): Are the spores alive and active?

Spores were stained to determine whether they were metabolically active, alive, and capable of functioning.

4. Germination Assay: Can the dormant spores activate?

Sound tested whether spores could exit dormancy and produce hyphae — an essential precondition for root colonization.

5. In Planta Root Colonization Assay: Can the AMF colonize roots?

Sound grew plants with the inoculant and used microscopy plus molecular methods (PCR & qPCR) to confirm real colonization.

After evaluating more than two dozen commercial AMF products ranging from home-garden inoculants to agricultural formulations, our Research Scientists reached a clear conclusion:

Very few AMF products on the market passed basic quality standards, much less our stringent ones. 

“Most of the products we tested contained spores that were already dead,” Anne notes. ​“Others had so few spores that you’d need to apply 10X or even 100X the recommended rate for it to do anything. They may as well have been a bag of sand.”

But Sound’s Research Scientists became intrigued by one product that continuously stood out by exceeding strict quality standards. Sound’s quality assessment was validated by successful field trials. Sound brought the product, now known as BLUEPRINT, to market in 2024. Vetting BLUEPRINT took several years, but ​“it’s the best commercial AMF product we’ve seen,” Anne adds. 

BLUEPRINT consistently passed all five assays and the lab continued to observe germination, root colonization and AMF DNA within the root structure. ​“I wanted to make sure the product was tested at different points in time up until the expiration date, so that no matter when growers use the product, they can trust the spores in BLUEPRINT are still alive and well” she says. 

Sound’s Research Team continues to test each new batch of BLUEPRINT in the lab for viability and germination, and all batches are retested every six months to ensure it passes high quality standards. 

This level of monitoring is uncommon but essential to ensure growers are achieving consistent results in the field. 

Learn more about BLUEPRINT’s mode of action here.
Learn more about our findings from the lab here.

In order to get the most benefit from AMF, it’s critical that they establish a relationship with the crop, which can be challenging in modern agricultural soils.

That’s why Sound recommends pairing BLUEPRINT with SOURCE which mimics a signal that activates AMF spores to colonize plant roots. SOURCE stimulates the microbes that make nutrients available to AMF to then transport back to plants. 

In fact, when using BLUEPRINT alongside SOURCE, we’ve observed a consistent 2 – 3X increase in AMF colonization of roots.

Growers using BLUEPRINT continue to see many crop benefits including improved macro and micro nutrient uptake, enhanced soil structure, improved stress tolerance, protection against pathogens, and more access to water when it’s needed most.

SOURCE and BLUEPRINT deliver a consistent 84% win rate with 8+ bu/​ac on corn — view additional crop and regional-specific performance data here.

Don’t wait to give your soil the support it needs. Learn more about BLUEPRINT or contact us today to see how it can transform your fields.