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Seedling disease is a focus of recent research

Article cover photo
A recent research project explored the use of soybean seed treatments and seedling vulnerability to Pythium in cold, wet conditions. (Photo: Joseph L. Murphy/Iowa Soybean Association)

By Carol Brown, ISA environmental communications specialist

For farmers looking to save money on input costs (and who isn’t?), purchasing soybeans with seed treatments may be one area to look.

Years of tight margins means farmers look at everything in hopes of cutting costs without negatively affecting yields. While some costs — like fuel and rent — are difficult to trim, farmers can take a closer look at seed treatment options.

“There are definitely conditions when farmers need to use seed treatments, but I don’t think they’re needed on every field on every single planting,” said Alison Robertson, a plant pathologist at Iowa State University (ISU). “Based on my research through the Iowa Soybean Association (ISA), we rarely see a yield increase from having a seed treatment.”

Through the project “Developing tools to protect soybean stand from seedling disease caused by Pythium species,” funded by ISA and the North Central Soybean Research Program (NCSRP), Robertson explored the soybean seedling disease caused by Pythium. She wanted to improve the understanding of soybean and Pythium interaction as one goal of the research project. Another goal was to develop a tool that farmers could use to make seed treatment decisions.

Robertson’s research started with focusing on the vulnerability of the soybean seed to Pythium after planting in cold, wet soils. Her research team focused on cold, wet conditions at one, two, four and seven days after planting and the risk of seedling disease at each stage. Soybeans germinate very quickly or more slowly depending on soil temperature.

 “We found out that when planting soybeans early, under good conditions, and a wet, cold front comes through within four days, there is more chance of Pythium infection, which could cause a reduction in plant stands,” said Robertson.

The researchers studied four soybean species at the very early germination stage, when the soybean was most susceptible to infection. They found that just as the seeds were starting to germinate, and the roots were still very young, the soybeans were most affected by Pythium.

“Once we got past five, six or seven days of growth, they got more resistant to infection,” Robertson said.

When using a seed treatment, the effects of those cold, wet conditions after planting were mitigated, based on Robertson’s NCSRP research. But seed treatments cost farmers $14 an acre and upwards, making it tough to pencil a profit in years of tight returns, she said.

“Farmers need to have a two-bushel yield increase just to see a return on investment,” said Robertson. “Right now, the price of soybeans isn’t great, and farmers are trying to cut inputs wherever they can.”

The other goal of the project was to expand the research model APSIM (Agricultural Production Systems sIMulator) with Sotirios Archontoulis, ISU professor of agronomy.

APSIM is an internationally recognized interactive tool developed in 2007 by scientists in Australia. Researchers around the globe are working on improving the model, currently consisting of 80 simulation modules, which is where Archontoulis is involved.

The APSIM model can help farmers when making decisions for emergence scenarios. Robertson has worked with Archontoulis to improve soybean emergence data and added seed treatments as an option. By entering details such as planting date, seeding rate and depth, soil moisture and other information, the model can estimate the time to reach 50 percent emergence and the number of plants emerged for each scenario. By changing factors such as seeding rates and seed treatment, the outcomes may change. A farmer could experiment with different scenarios and make decisions based on the scenario that best fits their production system. Unfortunately, the model is not readily available for farmers at this time. But Robertson and Archontoulis are working to change this.

“We hope to receive funding to develop the APSIM model into a web-based tool that would be more widely available,” said Robertson. “We have some grant proposals out there for this specifically.”

Farmers can get help using the APSIM model now by contacting their ISU Extension and Outreach field agronomist or the ISU Agronomy Department.

Contact Carol Brown at

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