Released April 4, 2008
EAST LANSING, Mich. -- As if soybean growers don’t have enough to think about, last fall’s widespread occurrence of green stem disorder is adversely affecting the quality of soybean seed available to plant this spring.
According to Mike Staton, Michigan State University (MSU) Extension educator and Soybean 2010 coordinator, the green stems delayed harvest operations, exposing the seed to repeated wetting and drying cycles. That reduced the thickness and integrity of the seed coats.
“When seed was finally harvested, it was difficult to adjust combines to be both gentle to the tender seed coats and also aggressive enough to remove the green plants,” Staton says. “Mechanical damage occurs when the seed embryo, which is near the surface of the seed coat, is bumped or hit. This causes a break or bruise to the radicle (root) of the germinating soybean plant. Depending on the severity of the damage, some of the plants grown from these seeds die, and others may have weak root systems.”
Three factors contributed to mechanical damage this year: seed coat deterioration, green plants and dry seed. Mechanical damage is often not detectable with the naked eye and should be determined with laboratory tests such as the tetrazolium (Tz) test.
In the Tz test, individual seeds are stained, dissected and evaluated for breaks or damage to the embryo to determine viability and damage. Warm germination results printed on the seed tag may not completely reflect the total mechanical damage. The warm germination test indicates how the seed will perform under ideal conditions and may not predict how the seed will perform when planted into the cool, wet soils common with early planting.
Staton cautions seed suppliers and growers to handle all soybean seed with great care to avoid further mechanical damage to the seed coats or the embryos. Growers may want to determine the quality of their seed lots by asking for Tz or cold germination test results from seed suppliers.
“If the information is not available, consider having the seed tested by the Michigan Crop Improvement Association,” Staton says. “With test results in hand, growers can rate the relative quality of their seed lots and determine their planting order -- always plant your highest quality seed first and your lowest quality seed last.”
Staton also suggests that growers who aren’t sure of the quality of the seed they are using consider delaying soybean planting until ideal conditions exist. They can also consider increasing seeding rates to achieve higher plant populations.
If planting into ideal conditions, use the warm germination test information to adjust seeding rates, and consider protecting seed with seed-applied insecticides and/or fungicides this year. These products will not improve the vigor or the germination of poor quality seed, but they have been shown to improve emergence in seed with reduced vigor.
MSU and the Michigan Soybean Promotion Committee will continue to research green stem to find answers to the questions this phenomenon generated this fall. Soybean producers can learn more about green stem by participating in regional corn and soybean research updates and Soybean 2010 educational programs.
For more information about improving Michigan’s soybean crop, visit the Soybean 2010 Web page at http://web1.msue.msu.edu/soybean2010/. Soybean 2010 was developed to help Michigan growers increase soybean yields and farm profitability by 2010. Funding is provided by MSU Extension; Project GREEEN (Generating Research and Extension to meet Economic and Environmental Needs), the plant industry initiative at MSU; and the Michigan Soybean Promotion Committee.
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http://anrcom.msu.edu/press/040108/040408_soybeangreenstem.htm
Contact: Laura Probyn, (517) 432-1555, ext. 171
