What the research measured
Independent corn and soybean field results show no yield gain. Iowa 2019 strips differed by 4 bu/ac in corn and 2 bu/ac in soybean, inside LSDs of 11 and 14; Nebraska 2019 measured 226 vs 235 bu/ac, a 9 bu/ac loss (P=0.003); Alabama’s five soybean site-years (2022–23) showed no statistical difference among any treatments, with the Glomus seed treatment ranging 36.4–70.9 bu/ac against checks of 41.7–72.9. A 2024 Kansas assessment of 23 retail inoculants found half produced no root infection and eight colonized no pot at all. A meta-analysis of 38 wheat field trials, mostly with research inoculants, reported higher grain yield on average.
Three US on-farm or research-station trials in corn and soybean (Iowa, Nebraska, Alabama; 2019–2023), one greenhouse assessment of 23 US retail products, and one global meta-analysis of wheat field trials. No multi-site US corn or soybean trial of a named product was found.5 independent sources.What it is. Propagules of arbuscular mycorrhizal fungi (the MycoApply line uses four Glomus species: G. intraradices, G. mosseae, G. aggregatum and G. etunicatum) applied in-furrow at planting, either as a liquid concentrate tank-mixed with starter fertilizer (EndoPrime SC: one gallon treats 64 acres, 2 oz/ac in the Nebraska trial) or as a 2 lb/ac granular. The fungi are meant to colonize roots and extend nutrient and water uptake; they are already present in most farm soils.
Study conditions and limitations
- Product quality varies: in the Kansas assessment, 8 of 23 inoculants showed no fungal colonization in any pot, 50% produced no infection in sorghum, carrot or lettuce, the best commercial product reached about 10% infection potential, enumerated spores were under 2% of labeled propagules, and 5 products carried the root pathogen Olpidium.
- Cost without a measured return in the two Midwest trials: the Iowa cooperator paid $12.50/ac and recorded no yield effect; Nebraska costed EndoPrime SC at $8.66/ac and measured a $41.63/ac lower marginal net return.
- The Nebraska trial also recorded a lower early-season stand with the product (21,619 vs 22,571 plants/ac on June 5), with no difference in the September count or in stalk rot.
- Alabama’s trials were seed-applied to soybean in no-till rye residue at two to three stations over two seasons; they are not corn and not in-furrow.
- The wheat meta-analysis found response depended on soil organic matter, pH, total N, available P, texture, climate and the fungal species inoculated, and did not evaluate retail products or US corn.
- OMRI status differs by formulation: Mycorrhizal Applications lists its Injector Endo powder as OMRI Listed, while the EndoPrime SC product page does not mention OMRI.
Read the sources · 5
- MycoApply Soil Inoculant for Corn and Soybeans ↗
Four replications of two treatments in each of a corn and a soybean field, MycoApply at 2 lb/ac in-furrow at planting for $12.50/ac: mean corn yield 248 bu/ac with a 4 bu/ac difference between treatments (LSD 11), mean soybean yield 61 bu/ac with a 2 bu/ac difference (LSD 14); the product had no effect on either crop and only added cost.
- Impact of In-furrow Applied Mycorrhizae Fungi to Non-irrigated Corn ↗
Seven replications of MycoApply EndoPrime SC at 2 oz/ac in 4 gal/ac 10-34-0 starter on no-till rainfed corn: 226 vs 235 bu/ac for the untreated check (P=0.003), and $857.46 vs $899.09/ac marginal net return at $3.83/bu corn and $8.66/ac product, a 9 bu/ac and $41.63/ac shortfall.
- Evaluating Microbial Seed Treatments for Alabama Crops (ANR-3259) ↗
Soybean seed treatments at two to three research stations in 2022–23, including a four-species Glomus mix: the mix yielded 40.7 vs 40.8 (EVS 2022), 25.2 vs 23.5 (TV 2022), 70.9 vs 72.9 (EVS 2023), 65.0 vs 63.8 (TV 2023) and 36.4 vs 41.7 bu/ac (PARU 2023) against the untreated check, and yield P>F was not significant at every site-year.
- An assessment of twenty-three mycorrhizal inoculants reveals limited viability of AM fungi, pathogen contamination, and negative microbial effect on crop growth for commercial products ↗
Greenhouse assessment of 23 retail inoculants under organic conventions: eight produced no fungal colonization in any pot, 50% gave no infection in sorghum, carrot or lettuce, the best commercial product reached about 10% infection potential, spores were under 2% of labeled propagules, and five products carried Olpidium. With fertilizer effects removed, 13 commercial products were neutral for crop growth, two inhibited it and one promoted it, while every laboratory-grown culture promoted growth.
- Responses of wheat to arbuscular mycorrhizal fungi: A meta-analysis of field studies from 1975 to 2013 ↗
Across 38 published wheat field trials with 333 observations, inoculation with AMF raised aboveground biomass, grain yield, harvest index and grain zinc on average, with grain yield tracking root colonization; response depended on soil organic matter, pH, total N, available P, texture, climate and the fungal species. Wheat, largely outside the US, with research rather than retail inoculants.
Before you buy, ask
- Is the formulation and application method I would buy the one that was tested?
- Was the comparison a yield gain at the same nitrogen rate, or held yield with less fertilizer?
- What happens to my result if I cut nitrogen and the product does not fix enough?
Record
- Sources checked
- October 12, 2026. Every figure shown is printed on the linked page; unit conversions are noted on the chart.
- Company response
- None yet. Makers and suppliers of this product can send corrections, additional trials, or a statement; it is published here, labelled, and never edits the research summary. Send a correction →