What to do about soybean quality concerns

While soybean yields were good (even above average) last year, seed quality has been a concern for the next crop year. In many areas, wet weather delayed harvest and led to increased grain moisture. In some cases, several cycles of this delay occurred before beans could actually be harvested. 

The increase in days of mature soybeans remaining in the field reduced the seed quality, with soybeans sprouting or rotting in pods, or pods shattering and releasing the soybeans to the ground.

What’s the big deal about soybean seed quality?

The wet conditions and extended harvest gave rise to a variety of seed diseases.

Two of the most common soybean diseases we saw were:

  1. Phomopsis seed decay (Diaporthe longicolla): Attacks soybean seed that are shriveled or have a cracked seed coat. Often times phomopsis can be seen on the seed coat as a chalky white substance.

  2. Purple seed stain (Cercospora kikuchii): Appears as purple seed or seed partially covered with purple staining.

These diseases and others may be more likely to appear throughout the next growing season. Both diseases, if left unchecked, have the potential to lower future germination rates significantly.

The presence of these diseases also means seed treatments could  be especially important next year.

The seed treatments will not increase the germination rate, but will protect the soybean seed from further degradation. Be prepared to apply a fungicide if and when the need arises.

What the germination tests are telling us

Cold germination tests done in Indiana and Arkansas show germination is down roughly 10 percent from normal at 80 percent germination. Accelerated aging tests were also performed — this test subjects the seed to 72 hours of high heat and humidity before the germ test. Those results showed 53 percent germination (25-32 percent) less germination than back in 2017.

Soybean seed options

Keep in mind that germination numbers vary by variety, and some varieties may not be available this spring due to low germination numbers. Be prepared to make some new picks where your soybean seed is concerned; in fact, now would be a excellent time to visit with your seed supplier about your soybean seed quality and options.

Emergence numbers

If you wind up planting lower germination seed, first do some back of the napkin emergence math.

If you normally plant 160,000 of 94 percent germ seed, you should have a final stand of 150,400 plants per acre.

Planting the same amount of 80 percent germ soybean seed should have final stand of 128,000 plants per acre.

You can increase seed drop to try and achieve the same final stand, but this doesn’t always translate into increased yield.

Low germination doesn’t necessarily mean low yields.

Low germination years have happened in the past, and they rarely result in overall lower yields. You might see lower yields due to low germination combined with other production factors, such as drought, heat, disease and weeds. Diligent scouting will help you to protect your soybean yields by managing all of the potential challenges and pressures associated with soybean production and performance.

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Sources:
https://www.canr.msu.edu/news/thin_soybean_stands_can_produce_surprisingly_high_yields
https://www.dtnpf.com/agriculture/web/ag/perspectives/blogs/ag-weather-forum/blog-post/2018/12/06/lower-soybean-seed-germination-2019

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