WESTERN PRODUCER — The hyperbole around biologicals and what they can do for crop production sounds like 10 million crickets in a suburban backyard.
There’s a lot of noise around biologicals, and for good reason. Soil contains millions of bacteria, fungi and other microbes that perform vital functions for plants.
As a result, global agri-science firms and dozens of start-up companies are trying to harness those biologicals and develop products that farmers can use.
Maybe a unique bacterium could be added to the soil that would increase corn yields by five per cent in Iowa, or a microbe could control soil diseases in a Saskatchewan canola field.
These biological products have potential, but the noise and hype may have got ahead of the science, says a plant scientist and soil microbiology expert from the University of Kansas.
“We’re at this really interesting point where we have all these results coming out of the lab that are extremely promising and tell us that the potential is there for products like this to make a huge difference,” said Maggie Wagner, who specializes in the interaction between plant genetics and the community of bacteria and fungi in soils, sometimes called the soil microbiome.
Unfortunately, when that unique species of bacteria is applied to the soil in real world conditions, its performance often disappoints.
“The products that focus on addition of microbes into the (soil) system tend to have inconsistent results,” Wagner said.
Field trials on nitrogen-fixing biologicals conducted by Manitoba Pulse & Soybean Growers from 2019-23 found that the commercial products were not effective on peas, dry beans and soybeans.
“So far, we’ve tested 12 products over 28 trials in three different crops…. We’ve not seen a yield increase with any of these products that we’ve tested,”” said Laura Schmidt, a production specialist with MPSG, who is 99 per cent confident in the results.
“I’m leaving that one per cent of the time where we might find this biological product that’s actually going to perform. That is something we would like to find.”
The effectiveness of biological products is likely higher than one per cent, but there’s a list of reasons why a single species of bacterium, added to the soil, fails to deliver results:
The pH of the soil is too high or too low for the bacteria to survive.
It’s too dry for the microbe.
There’s too much competition from other microbes in the soil.
Too much variability exists in the established community of microbes.
“The microbiome in the soil is going to vary quite a bit (within a field and from field to field),” Wagner said.
“We think that has a big impact on whether these (added) microbials are able to persist or not.”
A different approach
Instead of adding another bacterium to the soil and hoping it can outcompete the other micro-organisms, Wagner has proposed another way to improve the relationship between crops and soil microbes.
In a paper published in 2021, Wagner suggested that scientists could change the crop’s genetics so the plants work in synergy with the life in the soil.
“One potential method … is to alter host (plant) genetics to promote the recruitment and growth of beneficial microbes,” she wrote in a paper called Plant Genetics as a Tool for Manipulating Crop Microbiomes : Opportunities and Challenges.
As an example, there could be a bacterium that helps wheat use nitrogen in the soil. Maybe it’s possible to breed the crop so it supports and assists that species of bacteria.
“Imagine you have a particular beneficial microbe … that has an ability to (consume) some chemical that the plant can produce,” Wagner said.
“If the plant is optimized to produce that chemical, that would set up a situation where … that beneficial microbe will have a competitive advantage.”
In addition to that genetic change, farmers could add the microbe or bacteria to the soil to achieve the desired result — in this hypothetical case, deliver more nitrogen to the crop.
This scenario is comparable to bacterial inoculants for soybeans, which help develop nodules on soybean roots and fix nitrogen for the crop.
Wagner admitted that this research is in the conceptual phase. Plant breeders are not developing new varieties of wheat and corn so that they promote the growth of certain bacteria in the soil.
The science isn’t ready for that.
“There is a ton of evidence that plant genes do matter for the microbes that associate with their roots,” Wagner said.
“I don’t think the basic research into understanding what those microbes are doing for the plan t… and which plant genes would make a difference … (it’s) just not there.”
Early days
Wagner is just one member of a much larger community of scientists who are trying to comprehend the soil microbiome and what it means for crop production.
Dozens of researchers are studying soil — in Saskatchewan, Nebraska, Illinois and elsewhere —to understand how soil bacteria and fungi are different from one region to the next.
“The vast majority of microbes in the soil have never been grown in a lab…. We don’t know what they do. There is a whole lot of research going into that,” she said.
“We have barely scratched the surface of understanding and possible functions of all these microbes. That is a massive area of research.”
