Research Highlights

Research Highlights
Optimizing New Jersey Soybean Planting Populations for Yield and Profit

Differences between soybean planting populations were not obvious at the New Jersey demonstration site. Photo: Kate Brown, Rutgers Cooperative Extension

By Laura Temple

New Jersey farmers typically seed soybeans at a rate between 150,000 and 200,000 seeds per acre, based on long-standing state recommendations. However, their profit margins are shrinking as input costs increase.

“Inflation has driven up input costs and current supply chain disruptions have led to market volatility,” says Kate Brown, Rutgers Cooperative Extension program associate in Burlington County. 

She notes that existing planting density recommendations for New Jersey soils don’t account for improved technologies like seed treatment, breeding for improved vigor and herbicide tolerance. These advances often increase germination rate and yield.

“Data from other states suggests that planting populations can be reduced while maintaining yield, and more importantly, profits,” she adds. 

Brown took the first step in exploring how this applies in New Jersey soils by staging a demonstration plot with lower planting populations in 2022. The New Jersey Soybean Board invested checkoff funds in this demonstration plot, a first step toward updating state planting recommendations.

“We wanted to look at lowering soybean seed costs to help the bottom line for our farmers,” she says.

Burlington County has an ideal location that provides a unique opportunity to explore questions like this: a county-owned field that can host both field trials and on-farm research. 

The New Jersey soybean planting population demonstration plot was planted with a no-till drill in narrow 5.5-inch rows. Photo: Kate Brown, Rutgers Cooperative Extension

Brown’s demonstration included replicated plots of a Maturity Group 3 hybrid at seeding rates of 180,000, 150,000 and 130,000 seeds per acre. The cooperating farmer planted all the plots in 5.5-inch rows with a no-till drill. The seeds were treated, and they were managed identically throughout the season.

“Research has shown that soybean plants are able to modify their branching to maintain a constant yield across a range of planting densities.” she says. “When we asked farmers to identify the different planting populations at the demonstration site during a twilight meeting mid-season, they weren’t able see a difference.”

However, the combination of drought and severe heat in late July and August impacted yields in the demonstration plots and across the region. 

“The drought may have inhibited soybean adaptability in lower populations,” Brown reports. “Though the populations of 150,000 and 130,000 seeds yielded statistically the same, they showed a 10-bushel-per-acre yield drag and no economic advantage compared to the 180,000 seeding rate in the 2022 growing conditions.”

However, she says they observed trends that warrant further evaluation. She plans to increase the scale of this demonstration into a full research study, including on-farm plots, with a wider range of planting rates. Additional locations would also allow observations in both the Coastal Plains soils along the Atlantic and the heavier soils found further north and west in New Jersey.

“Multiple years of data through a range of conditions and larger plots will help us determine if the recommended planting rates can be reduced for New Jersey farmers,” Brown says.

Kate Brown profile

Published: Feb 13, 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.