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Research Highlights

Research Highlights
Variable Soybean Seeding Rates Maximize Profit, Minimize Risk

Photo: United Soybean Board

By Laura Temple

Seed has become the single most expensive input cost for soybean production, which is why Dr. David Holshouser, Associate Professor and Extension Agronomist with Virginia Tech University, focuses on seeding rate recommendations.

“The goal is to plant the least amount of seed to reach maximum profitability,” he explains. “At the same time, farmers should understand the risks of yield loss at a given seed population rate. Saving $10 or $15 per acre in seed costs while maintaining yield potential can make a big difference in profitability.”

For the past few years, Holshouser has been conducting both small-plot and field-scale seeding rate research to develop and test site-specific recommendations. The research, funded by the Virginia Soybean Board, aims to factor yield, profitability and risk management into seeding rate recommendations, among other agronomic variables.

He is gathering data for both full-season and double-crop soybean production systems, and he is accounting for environmental variability. During the 2020 growing season, Holshouser and his team compared seeding rates in 10 small research plots, a full-season and a double-crop plot in each of Virginia’s five agricultural regions. In addition, five field-scale trials were conducted with farmer cooperators, looking at seeding rates that vary above and below their typical practices.

Throughout the season, in-field measurements and drone-collected data helps Holshouser understand how various seeding rates respond to their environments. At the end of the season, yield data is layered with this information to identify “sweet spots” for seeding rates in variable environments.

“The data we are seeing is validating the recommendation that lower seeding rates perform well in highly productive soils, while higher seeding rates are needed in less productive environments,” Holshouser says. “This is counter-intuitive, and the opposite of corn.”

He explains that in productive soils, soybean plants grow well, filling in whatever space they can with leaf area to support pod production and fill. Soybeans compensate well for gaps in seeding in these environments. However, in less productive soils, soybeans find it harder to fill in space and grow well, so higher seeding rates help reach maximum yield potential in those environments.

At the same time, Holshouser is evaluating the risk of not meeting yield potential due to lower seeding rates. Understanding that risk and balancing it with seed cost can help farmers optimize soybean profitability. As Virginia soybean farmers select seeding rates ideal for their cropping system, location, environment, fields and soil types, they will have recent data on how popular varieties perform under Virginia environments.

“The long-term goal is to develop updated variable rate seeding recommendations between and within fields,” he says. “Assuming just a 1percent gain in net profit from this research, nearly $2.1 million could be added annually to the value of Virginia’s soybean crop. And, the seeding rate data we collect will be valuable to soybean growers throughout the country.”

Holshouser is sharing this work with farmers in a variety of ways. For example, a video produced for the Virginia Ag Expo explains the work and its potential benefits for soybean farmers.

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