Research HighlightsTesting Emerging Input Recommendations
By Laura Temple
Soybeans can grow fine with just the basics: sunlight, water and soil. But additional products and recommendations flood the market, claiming to help soybeans thrive — and boost yields. From biologicals to micronutrients, separating valuable inputs from snake oil can pose a challenge for farmers.
Jeremy Ross helps farmers sort through those claims with his unbiased trials, conducted as a professor and soybean extension agronomist for the University of Arkansas System Division of Agriculture’s Cooperative Extension Service. Thanks to the Arkansas Soybean Promotion Board, Ross has funding to test emerging recommendations for soybeans and share the results with farmers.
“Farmers have lots of questions about new products or recommendations from their suppliers,” Ross says. “Many of my trials seek to answer those questions.”
For example, he conducted seeding rate trials with varieties that include dicamba and 2,4-D herbicide-tolerant technology. He found existing planting rate recommendations hold true, but given rising seed costs, he believes it was worth checking.
His work includes local trials, as well as involvement in multi-state research projects through Science for Success that produce data from a wide range of conditions in just a couple years. For example, Ross and his team have participated in studies examining biological seed treatments, added fertilizers and foliar feeding.
Biological Seed Treatments
The term “biologicals” refers to products created from naturally occurring microbes or their synthetic equivalents. A wide range of biological seed treatments on the market add bacteria or fungi to soybean seed with claims of improving soil interaction for germinating soybeans. Multi-state trials in 2022 and 2023 focused on seven such products, including plots at two Arkansas locations.
“Overall, the first year of trials didn’t show much benefit from these products,” Ross reports. “In a few locations, products that include rhizobium bacteria that help soybeans fix nitrogen (N) did benefit yield.”
That observation aligns with his previous research. He found inoculating soybean seed planted after mid-May in Arkansas pays with significant yield increases compared to the cost of treatment. However, many of the new treatments available don’t appear to deliver that level of returns.
“Once we have two years of data from around the country, we expect to be able to determine when and where some of these treatments may make sense, if at all,” he says.
Nitrogen and Sulfur Fertilization
Based on yield goals and changing environmental conditions, emerging recommendations include fertilizing soybeans with N and sulfur (S). Again, Ross reports that in Arkansas trials and those in other regions, the extension agronomists did not see an economic impact from adding either N or S.
“Soils no longer get free S from the air with the Clean Air Act,” he explains. “However, most soils still have sufficient S to meet soybean needs. Unless fields have zero organic matter, we aren’t recommending adding S for soybeans — yet.”
He plans to continue monitoring this issue. Ross anticipates that recommendation could change in several years, as S in the soils is used over time.
Though soybeans fix N, anecdotes from some farmers suggest that adding it later in the season can boost yields. Ross has not been able to duplicate those results in his research.
“Likely those results are location-specific,” he says. “As long as soybeans have good nodulation, extra N isn’t needed.”
Many companies offer a variety of foliar micronutrient products that can be applied to soybeans mid-season. However, the Science for Success team did not see yield increases or a return on investment for these products in their trials.
“Plants are designed for nutrients to come through their roots, not their leaves,” Ross explains. “Plus, the rates of micronutrients in these products are a drop in the bucket compared to plant needs.”
He says foliar products do fit in specific situations. They can address known micronutrient deficiencies in-season. However, he considers that a short-term solution.
“It’s a band-aid for this season,” he says. “Foliar feeding doesn’t put nutrients into the soil system. That’s where plants need nutrients to truly improve the soil in the future.”
Published: Dec 18, 2023
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.