Production Blog
Pam Smith DTN\Progressive Farmer Crops Technology Editor

Friday 06/13/14

Evaluate Soybean Emergence

KANKAKEE, Ill. (DTN) -- My father used to worry about soybeans breaking their necks. During tough springs, our heaviest clay soils would often crust over enough to cause emergence problems.

Some soybean stands have been ragged in appearance this year, but specialists say to evaluate stands before replanting. (DTN photo by Pamela Smith

The fields I've seen so far this year seem to be hampered more by cool, wet, muddy conditions. Even the sandy soils I scouted outside of Kankakee, Ill., last week were showing some uneven stands -- although most of the stand issues I saw there I'd attribute to preplant residual burn.

Whatever the issue, replanting at this late date isn't always the answer. An Ohio State University release this week does a good job of detailing what conditions warrant replant.

Unless growers with uneven soybean emergence can determine that their seedlings are dead, they may want to hold off on replanting decisions, said Laura Lindsey. She is a soybean and small grains specialist with the college's outreach arm, Ohio State University Extension.

"Planting conditions weren't ideal this year, and some soybean stands may not look good right now," she said. "But you have to keep in mind that while stands may not look so great right away and emergence is uneven, soybeans will even out in most situations," she wrote.

First try to diagnose why plants aren't coming up before making any replanting decisions, Lindsey said. "When considering replanting soybeans, make sure to take into account the existing stand, yield loss due to late planting and the cost of additional seed," she said. "Soybean yield is decreased by approximately half a bushel per acre every day when planting later than mid-May."

Dig to see if seeds have germinated and perhaps have just not emerged. Growers who find dead seedlings or no seeds or seedlings should take a stand count to see how many plants are remaining, she recommended in the news release.

One way to estimate stand is to count the number of plants in 69.8 feet of row for a 7.5-inch row spacing. This represents one-thousandth of an acre, so 120 plants in 69.8 feet of row grown at a 7.5-inch row spacing represents a stand of 120,000 plants per acre.

"Soybean populations of 50,000 plants per acre yield approximately 15% lower than soybean populations of 116,000 plants per acre when planted in May, according to research by Ohio State's Agronomic Crops Team," she said. "But they still yield."

Estimates can also be done using 34.10 feet of row for a 15-inch row spacing or 17.5 feet of row for a 30-inch row spacing, she said.

Others use the hula hoop method for this planting stand exercise. Here's another good link if you're trying to decide whether to replant or fill in substandard stands: http://www.coolbean.info/…

That guide's title: "Think Twice Before Replanting Soybeans" sums up the current thinking on this agronomic question.

Pamela Smith can be reached at Pamela.smith@dtn.com

(AG)

Posted at 2:44PM CDT 06/13/14 by Pam Smith
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