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Soybean Field Observations in 2013

Soybean Field Observations in 2013

An agronomist looks at the season that was.

Mark Lawson has seen more than a few seasons come and go. Lawson, Danville, is an agronomy service rep for Syngenta, and also maintains a farm. In fact, he uses his farm to make observations and test and demonstrate various theories, products and practices.

Recently, he commented on observations he made in 2013 that have merit heading into another season. "There was quite a bit of green stem around this fall in soybean fields," he notes. "I didn't see a yield penalty for it, but it did make soybeans hard to cut."

In some fields there was more green stem on some soil types than others. Higher soils seemed to feature more green stem conditions.

Green stem returns: There was an ample amount of the green stem syndrome in soybean fields earlier this fall, especially on certain soil types.

"Draper heads went through these spots much more easily than platform heads," Lawson observes.

Nevertheless, the green stem was enough to cause some combining headaches and need for adjustment, even in modern combines. Depending upon the model the green material could build up and cause blockages somewhere in the machine.

That isn't the only observation Lawson made about soybeans this year. "Based on what I saw, positive results from fungicide application on soybeans came when application was made between the R 3 and R 4 reproductive stage, and no later than R 5," Lawson says.

When to spray soybeans with fungicide to get the best chance of a response has been an issue of contention recently.

According to the Corn & Soybean Field Guide published by Purdue University Crop Diagnostic Training Center, R 3 is defined as beginning pod stage, and R 4 is full pod stage. At full pod the pod is about ¾ inches long at one of the four uppermost nodes on the main stem with a fully developed leaf.

The R 5 stage is when seed in the pods at the same location is about one-third inch long.

That's a pretty narrow window for fungicide application. "Spraying too early or too late was not advantageous," Lawson concludes.

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