How to Evaluate Emerging Soybeans

Soybean. Photo: Thinkstock

COLUMBUS, Ohio – With the majority of soybeans now planted in Ohio and some plants beginning to emerge, growers statewide should evaluate soybean stands to determine if their crops are doing well or if they may need to consider replanting.

With high costs associated with replanting, most growers should carefully weigh all options before deciding to replant, said a field crops expert in the College of Food, Agricultural, and Environmental Sciences at The Ohio State University.

While most soybean growers across Ohio report good stands, a few growers are seeing damping-off and uneven emergence, said Laura Lindsey, a soybean and small grains specialist with Ohio State University Extension. OSU Extension is the college’s outreach arm.

“If soybean emergence is uneven, growers should determine the cause before making decisions on whether they need to replant,” Lindsey said. “Most reports I’ve heard from growers are that things are looking good right now, with a few reports from some growers of uneven soybean emergence because of dry soil.

“To determine the cause of uneven emergence, growers can dig up seed in an area of the field that has no plants emerged to see if the germinated seed is healthy and free of disease or insect damage. If the seed is healthy and germinated but just not broken through the soil, growers don’t need to worry because a little bit of rainfall will help it to continue to emerge.”

However, if growers find insects or diseases have affected the seed, they may want to consider replanting, she said.

Statewide, for the week ended May 24, soybeans are 71 percent planted and 38 percent emerged, according to the May 26 U.S. Department of Agriculture crop progress report. That compares to soybeans at 32 percent planted at the same time last year, with 10 percent emerged during that same period, the USDA said.

Topsoil moisture is 86 percent adequate to surplus in Ohio, with subsoil moisture at 92 percent adequate to surplus statewide, USDA said.

“Scattered showers occurred over the past week, however many areas haven’t had much rainfall in recent weeks, contributing to a growing seasonal deficit,” the USDA said in a statement.

Before replanting, growers should conduct a stand count, Lindsey said.

Previous research conducted by the Ag Crops Team at Ohio State indicates that soybean populations of just 50,000 plants per acre yield approximately 15 percent lower than soybean populations of 175,000 plants per acre, she said. 

“Also, keep in mind soybean yield is decreased by approximately half a bushel per acre every day when planting later than mid-May,” Lindsey said. “When considering replanting soybeans, make sure to take into account existing stand, yield loss due to late planting and the cost of additional seed.

“We recommend higher seeding rates when planting in June.”  

One way to estimate stand is to count the number of plants in 69.8 feet of row for a 7.5-inch row spacing. This count represents one-thousandth of an acre, so 120 plants in 69.8 feet of row grown at a 7.5-inch row spacing represents a stand of 120,000 plants per acre. 

Tracy Turner
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Laura Lindsey