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Research Highlights

Research Highlights
Determining the Impact of Foliar Nutrient Feeding on Soybean Yield

By Barb Baylor Anderson

Farmers across a wide range of U.S. soybean growing environments are interested in using foliar nutrient products to increase yield and profitability. But applying foliar fertilizers increases on-farm expenses and could decrease profitability where they are not associated with yield gains. 

In 2019 and 2020, universities in 16 states established field trials to allow scientists to better understand which growing environments may see a yield increase when foliar nutrient products are applied as a preventative measure. The goals were to identify the most effective products and to conduct economic analyses on the value of foliar fertilizers for maximizing soybean yield. 

Principal investigators on the checkoff-funded effort include: Emma Matcham, University of Wisconsin graduate student; Rachel Vann, North Carolina State University Extension soybean specialist; Shawn Conley, University of Wisconsin Extension soybean specialist; and Laura Lindsey, Ohio State University soybean and small grain associate professor. Other states involved include Arkansas, Florida, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, North Dakota, Oklahoma, South Carolina, South Dakota and Virginia.

Researchers found a significant difference in soybean yield among sites, but no significant difference among treatments or treatment-by-site interaction, concluding that there was no impact on soybean yield of evaluated foliar fertilizers applied prophylactically at R3.

“Six foliar nutrient products were selected with the input of industry professionals, applied to small plots and compared to an untreated control,” says Vann. “Products were applied at soybean growth stage R3 to align with commonly used fungicide and insecticide application timing.”

Various foliar nutrient products were tested in 20 environments in 2019 and 26 in 2020.

“Based on these 46 site years of data generated across the nation capturing many environments, we saw no impact on yield of the evaluated foliar fertilizer products applied prophylactically at R3,” says Vann. “Most research has consistently shown foliar fertilizer use is only valuable for protecting soybean yield when a visual nutrient deficiency has been detected. We recommend farmers invest in management areas that have been proven to have a consistent impact on yield.” 

Wisconsin’s Conley agrees in the absence of micronutrient deficiency symptoms, there is a low probability of a positive farm-wide return on investment for any of the products. He adds, “We can’t test everything, but there is a finite list of micronutrients and most of these products have some combination of a few or all that could impact yield. It’s not magic, it’s science.”

Vann contends it may be time to move the research in a fresh direction. “We have thoroughly investigated the value of these products in unbiased research trials and have found no impact on soybean yield. In my opinion, as Extension Specialists, we need to focus on efforts elsewhere in production areas that have been proven to most consistently protect and increase soybean yield.” 

Soybean farmers like Kris Folland, who chairs the Minnesota Soybean Research & Promotion Council Research Action Team from Halma, Minnesota, appreciates the work of researchers. 

“The soybean checkoff is important in helping fund projects such as production research. From improved genetics to best management practices for soybean aphid control and soybean cyst nematode management, farmers use these results to improve the bottom line,” he says. 

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.