A large-scale field study shows that treating farmland soil with mycorrhizal fungi can increase corn yields by 40% without the need for any additional fertilizers or pesticides, which is a very promising sign for ensuring and improving food yields. In the Swiss study, researchers mixed arbuscular mycorrhizal fungi (AMF) into the soil before sowing in 800 experimental plots on 54 corn farms.
This fungus occurs naturally in healthy soil and penetrates plant roots to form tree-like structures (sclerotia). When they branch, they increase the surface area of the plant's roots, which promotes nutrient uptake.
"On a quarter of the plot, mycorrhizal fungi increased yields by 40 percent, which is a huge improvement," said study co-leader Marcelvander Heijden, a soil ecologist at the University of Zurich and the Center for Agricultural Research.
When researchers investigated why one-third of soils produced little or even less, they found that healthy soil produced the same (or in some cases produced less) than healthy soil.
"We found that inoculation works best when there are already large numbers of fungal pathogens present in the soil," said co-first author Stefanie Lutz from Agroscope.
Fungi are considered the soil's first line of defense against plant-attacking pathogens that can significantly reduce crop yields. Thus, in fields with pathogens, yields can remain unchanged in the absence of fungi, whereas in fields without pathogen contamination, the beneficial impact of fungi on yields is lower. As beneficial organisms, fungi also help plants absorb nutrients from the soil.
Building on the extensive results, the team then used soil microbiome indicators to successfully determine plant growth changes in any given plot before sowing with 86% accuracy.
"We were able to predict the success rate of inoculation in nine out of 10 fields and therefore the harvest yield well in advance of the field season," says co-first author Klaus Schläppi from the University of Basel. "This predictability makes it possible to use the fungus in a targeted manner in fields where it can be effective. This is a key factor in developing these technologies into reliable agricultural methods."
The discovery could increase food production without the need for heavy use of pesticides and fertilizers. A 2022 United Nations report found that 40% of the world's soils are moderately or severely degraded and predicted that this proportion could rise to 90%.
How to effectively spread the fungus on a larger commercial scale remains to be solved, but "the results of this field trial represent a big step towards more sustainable agriculture," says Vanderheiden.
The research was published in the journal Nature Microbiology.