A couple of weeks ago, I attended a conference on producing high-yielding soybeans. The event was sponsored by the Michigan Soybean Board and the Indiana Soybean Alliance. The focus was on answering the following questions: Why haven't soybean yields gone up like corn? What is limiting our production?
The first and most talked about issue was disease. Soybean cyst nematode and white mold topped the list. Experts encouraged sending soil samples for cyst testing. Additionally, the Michigan Soybean Board will pay for type testing if the infestation meets thresholds.
It has been about 10 years since we identified race shift on one of our farms. Management tools for SCN include rotating to non-host crops and planting soybeans with alternate race resistance. Seed treatments such as VoTivo and N-hibit showed modest yield gains over untreated, however had little impact on reducing SCN counts.
Until this meeting, I had heard there may be ways to control white mold, but had never met anyone who was successful on a regular basis. Multiple fungicide treatments (with properly labeled fungicides) seem to be the key here.
The first treatment comes when the soybeans first flower, with follow up treatment(s) at key intervals through the season. In severe cases, a soil fumigant may be an option, though it is quite pricey. It is common for growers who have white mold to plant in wider rows and lower populations in order to have better air circulation through the crop canopy.
When to allow soybeans to stress and when to irrigate were also discussed. The resilient soybean plant can overcome early stress and still produce good to excellent yields. Continuing irrigation through pod fill is a key to pod and seed retention as well as seed size and weight. The recommendation to use some sort of irrigation scheduling progam was made as well.
The bottom line is for soybeans to break this current plateau, growers will need to implement a systems approach. Along with practices mentioned earlier, this approach will likely include techniques proven successful in other crops and vegetables. It may also include late season plant nourishment.
Ultimately, in order to increase yields, we have to stop treating soybeans as a secondary crop.
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