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Research Highlights
Impact of Soybean Planting Date on Growth Promoter Fit

Photo: United Soybean Board

By Laura Temple

Many growth-promotion products tout benefits for soybean production. Proprietary combinations of fertilizers, carbon, sugars, growth regulators and other ingredients crowd the input market, as companies continue to release new products.

“Farmers asked me about growth-promotion products,” says Andy Kness, an agricultural Extension educator with the University of Maryland. “Local suppliers were offering new products, but very limited third-party research existed to assess their fit in specific production systems. With tight soybean margins expected, farmers want to understand the potential return on investment for this type of product.”

With soy checkoff support from the Maryland Soybean Board, Kness conducted research trials comparing soybeans treated with several locally available growth-promoters. He tested eight products in 2019 and 10 products in 2020 at the Western Maryland Research & Education Center (WMREC) in Keedyseville and the Wye Research and Education Center (WYE) in Queenstown and summarized his findings.

“Overall, we saw no significant yield responses with the products in the trial,” he says. “There likely are applications where they do fit, but not in our standard Maryland soybean production systems.”

He also monitored emergence, vegetative growth and canopy height during the season. That trial data revealed one exception: the seed treatment product Take Off® ST, a combination of carbon, a growth promoter and a fungicide.

In side-by-side plots, soybeans planted at early and mid-season dates showed a statistically significant increase in relative yield with Take Off ST compared to untreated soybeans.

“Our trial in western Maryland, was planted earlier than our eastern location,” Kness explains. “In both 2019 and 2020, we saw significantly higher emergence in plots treated with Take Off ST at WMREC but just a small, statistically insignificant bump in emergence at WYE.”

These results led Kness to ask if soil conditions impact the fit of this product. In 2021, he looked at just Take Off ST at three different planting dates.

“I assumed that at earlier planting dates, cooler, wetter soils are more prone to slowing early soybean growth,” he says. “However, planting soybeans earlier is a growing trend in Maryland and many other regions.”

A combination of weather and equipment challenges caused the western Maryland location to be planted well before the trials in eastern Maryland. With planting dates spread from late-April to mid-June, Kness saw benefits at early and mid-season planting dates, but no difference at late planting dates.

He also observed differences between growing seasons.

“Although emergence improved significantly with Take Off St at early plantings in 2019 and 2020, there was no statistically significant yield response, likely because soybeans compensate well for reduced stands,” Kness explains. “However, in 2021 there was no difference in emergence, but there was a yield response, especially at the mid-May planting date at our western location.”

He looked at weather data for those three years and noted cooler, wetter April weather in 2019 and 2020, compared to excellent planting conditions in 2021.

“Data from these three years suggest that Take Off ST may help soybeans emerge in soils that are cooler and wetter, but may have little benefit for later planted soybeans,” he concludes. “That may be due to the fungicide component of this growth-promotion product. But this product could be a good fit for soybeans planted in April and early May.”

Kness believes more data is needed for firm recommendations. He plans to leverage the existing checkoff-funded research to garner industry support for continued study of the relationship between this growth-promoter and soybean planting date.

This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.