Research Highlights

Biological Seed Treatments: The Big Picture

In this article, you’ll find details on:

• Science for Success conducted more than 100 trials with biological seed treatments across 21 states in two years. 
• No active ingredients consistently provided statistically significant results when comparing the national average to the untreated control. However, the team observed some local, conditional responses.
• In-depth analysis of additional data beyond soybean yield may help identify places where biological seed treatments fit and offer an advantage.

By Laura Temple

From major companies to start-ups, countless ag input businesses are betting on biologicals. Their research and development investments have rapidly expanded the availability of products with biological active ingredients, like bacteria, fungi, plant extracts or algae extracts. Often they are applied as seed treatments, which has proven to be an effective way to deliver many of these new options.

Do these products deliver a return on investment in soybeans? 

Soybean extension specialists across the U.S. frequently hear questions like this from farmers. Because third-party data on these products was limited, they decided to collaborate through Science for Success to find answers. 

Science for Success is funded by the soy checkoff at national and state levels, allowing soybean extension specialists to collaborate on key research and outreach questions. By using identical research protocols across multiple soybean-growing states, they can quickly produce trial data across a wide range of environments and conditions. 

In 2022 and 2023, Science for Success took a close look at biological seed treatments.

“Biological active ingredients are very different than chemicals,” says Laura Lindsey, professor of soybeans and small grains at Ohio State University. “They are living organisms that need a host, in this case a soybean plant, and a conducive environment to thrive and provide the expected benefit.”

Lindsey served as the lead of this multi-state study, alongside one of her doctoral students, Fabiano Colet, who developed the trial protocol, coordinated logistics and gathered results. 

“Soybeans have a very complex biology, and introducing another biological factor just adds to that complexity,” she says. “With this project, we aimed to gather a broad range of data to help us identify general patterns and develop broad recommendations.”

Plant Growth Support

For these trials, the Science for Success team focused on biologicals that claim to support plant health and growth. These biologicals, often classified as inoculants or biostimulants, target improved nitrogen fixation, increased nutrient uptake or use efficiency, stimulated root growth and similar functions. 

“We developed our treatment list with a focus on active ingredients, the microbes themselves, rather than specific products,” Colet explains. “We see lots of product turnover because it’s a new, rapidly growing market.”

He says they based part of the treatment list on the results of a national survey asking farmers about their interest in 20 or 30 biological seed treatments. More than half the treatments tested each year came from survey responses. 

Active ingredients included common options currently available. Treatments included mixtures of multiple microbes from these and other groups. 

• Bacillus species can act as probiotics that influence nutrient availability and use, promote plant growth, fight off potential disease-causing organisms, and more. 
• Bradyrhizobium species play a role in fixing nitrogen.
• Glomus species form beneficial relationships with plant roots, potentially impacting nutrient uptake and plant resilience to stress or disease.
• Trichoderma species have been shown to suppress disease and promote plant growth.

“The products used in the trials had lots of handling variability, because they have to be alive when applied,” Colet notes. “The label requirements include storage timing and temperature, application timing prior to planting and more, to ensure the microbes live and perform as expected. We looked at products that can be applied either by farmers or retailers.”

Science for Success participants carried out research with these common protocols at 49 locations across 17 states in 2022 and at 52 locations across 20 states in 2023. Results from those 101 site-years covered plots from North Dakota to Florida and Nebraska to South Carolina.

Initial Results

In addition to collecting soybean yield data, trial participants collected soil samples, soybean tissue samples during reproductive growth, field history, soybean variety information, harvested soybean content samples, environmental data and more.

“Based on the data from these trials, nothing worked universally,” Lindsey reports. “In 2022, none of the microbes we looked at had statistically significant results compared to the untreated control. In 2023, we saw a national increase of 1.6 bushels per acre with Bradyrhizobium.”

She notes that they observed local, conditional responses to some active ingredients in some situations. 

“Those isolated results raised more questions,” she says. “Was it the weather? Something already in the soil?”

She notes that differences between Science for Success in-field research and company information could relate to the rapid development of the market and its products. She explains that often the way something works in the greenhouse is different than how it responds in the field, because so many other factors influence results.

For that reason, the team collected as much information as possible from these trials. However, the volume of data collected made it challenging for Lindsey and Colet to identify patterns initially.

“We have hired a statistician to review the data,” Lindsey adds. “We expect that more in-depth analysis will help us understand the fit for specific biological seed treatment options.”

From that in-depth analysis, Science for Success will develop outreach materials designed to answer farmer questions about biological seed treatments. Lindsey and Colet aim to have that information available as planning for 2025 starts.

In the meantime, Lindsey offers the following initial recommendations to farmers considering biological seed treatments for soybeans.

• Consider doing in-field comparisons before going all-in on a product.
• Follow product label directions, remembering that the active ingredients need to be alive when applied.
• Keep in mind that any yield increases are often small.
• Watch for additional information from Science for Success after the in-depth analysis has been completed.

Published: Jul 1, 2024

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.