ROCKVILLE, Md. (DTN) -- Remember how wet and miserable it was last fall in much of the Midwest and South?
Your soybeans do.
Experts are urging growers to be on alert for soybean seeds with lower germination rates, less vigor and more seedborne disease this year, after a prolonged, wet harvest compromised seed quality in 2018.
Mike Stahr, seed lab manager at Iowa State University Seed Science Center, oversaw about 10,000 soybean seed samples from this past fall and winter. They had an unusually high level of seedborne diseases and lower-than-average germination rates, he said. "But this situation goes well beyond Iowa," he added.
Growers should check soybean seed bag tags closely for germination rates listed by the company, and make population adjustments as necessary. Some farmers might also benefit from re-testing germination rates closer to planting time, as seed quality can decline in certain storage conditions. And finally, growers may need to invest in the proper fungicide seed treatments to control seed- and soil-borne diseases.
PICK FUNGICIDE TREATMENTS CAREFULLY
Moldy and disease-damaged soybeans are usually sorted out during commercial seed cleaning and conditioning, but some infected soybeans do make it through, Stahr noted.
Seed labs saw high levels of Phomopsis seed decay in particular this fall, with Fusarium infections also running higher than normal. Fungicide seed treatments can help control these infections and improve germination and emergence, Stahr said.
"A dead seed is a dead seed and a seed treatment can't fix that," he cautioned. "But within a seed lot, you might have some seedlings that have Phomopsis present, and a fungicide seed treatment can stop that from spreading beyond the little area that it is on."
Don't assume any fungicide will do. "Various seed treatment classes and active ingredients do not work equally well against all pathogens," a team of University of Nebraska crop scientists noted in a recent CropWatch article. "Thus, it's important to understand which disease(s) have been or may be problematic in your fields and select products or a diverse combination from multiple fungicide classes."
Look for a laboratory that will test for soybean seed disease, and check the efficacy of fungicide seed treatments, using this CropWatch publication: https://cropwatch.unl.edu/….
Germination rates are indeed running lower than average this year, according to seed testing facilities. "I think our average germination rate was around 80%, but most samples fell between 45% and 85%," Stahr said of the Iowa State Seed Science Center. "In a normal year, most beans are in the 90%-range."
The Nebraska Crop Improvement Association reported soybean germination rates ranging from 43% to 98% germination, down from a more typical range of 88% to 98%, the Nebraska scientists noted.
The Association of Official Seed Certifying Agencies (AOSCA) sets a minimum germination rate for certified seed at 80%, so most growers are unlikely to see rates below that on their seed bag tags. Seed companies also put their seed soybeans through cleaning and conditioning procedures that sort out the majority of diseased, warped or broken soybean seeds, Stahr added. "Seed conditioning gets better every year," he said.
However, growers might consider re-testing a sample of their soybean seeds closer to planting time, as germination rates and seed disease can change under certain storage conditions, Stahr and the Nebraska scientists said.
Seed testing laboratories can do these additional tests if necessary, but growers can also do their own tests at home, Stahr said. "You can use a damp -- but not overly wet -- paper towel or hand towel and keep it at room temperature, and see how many seeds sprout," he said. See more guidance from University of Wisconsin Wheat and Soybean Extension Specialist Shawn Conley here: http://www.coolbean.info/….
Some growers might want to adjust their planting population on low-germination seed to ensure they still reach their targeted final stand. "If you're shooting for a 120,000-plant-per-acre stand, and the germination rate is 80% rather than the 90% you usually plant, increase the seeding rate by the relative difference. In this example, by 10%," the Nebraska scientists explained. "A lot of things can kill your stand after emergence and you don't want to short change potential yield early in the season."
But also keep in mind that soybeans are a resilient crop, Stahr added. They can branch to fill out thin spots in the field, and research suggests that lower soybean seed populations can be economically sound and even help limit the growth of certain diseases such as white mold. See work from University of Wisconsin Soybean and Wheat Extension Specialist Shawn Conley here: https://coolbean.info/….
Illinois farmer John Werries, for example, received soybean seed with 85% germination rates, down from 90% last year, but not low enough to worry him. "Our soybean seed germination is not enough lower than normal to change seeding rate," he said.
"We feel fairly confident that there are adequate controls in place to ensure that soybean seed quality is not an overwhelming issue," added Charles Williams, who farms in northeast Arkansas. "Our soybean planting population will be around 150,000 seeds/acre, and we consider a consistent 80,000 to 100,000 to be an adequate, workable stand in most cases."
For more details on germination, disease and population decisions, see the University of Nebraska Crop Watch article here: https://cropwatch.unl.edu/…, an article from the Iowa State Seed Science Center here: https://www.seeds.iastate.edu/…, and the Crop Protection Network here: https://cropprotectionnetwork.org/….
Emily Unglesbee can be reached at Emily.firstname.lastname@example.org
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